About Christian Timmerer

Christian Timmerer is a researcher, entrepreneur, and teacher on immersive multimedia communication, streaming, adaptation, and Quality of Experience. He is an Assistant Professor at Alpen-Adria-Universität Klagenfurt, Austria. Follow him on Twitter at http://twitter.com/timse7 and subscribe to his blog at http://blog.timmerer.com.

MPEG Column: 137th MPEG Meeting (virtual/online)

The original blog post can be found at the Bitmovin Techblog and has been modified/updated here to focus on and highlight research aspects.

The 137th MPEG meeting was once again held as an online meeting, and the official press release can be found here and comprises the following items:

  • MPEG Systems Wins Two More Technology & Engineering Emmy® Awards
  • MPEG Audio Coding selects 6DoF Technology for MPEG-I Immersive Audio
  • MPEG Requirements issues Call for Proposals for Encoder and Packager Synchronization
  • MPEG Systems promotes MPEG-I Scene Description to the Final Stage
  • MPEG Systems promotes Smart Contracts for Media to the Final Stage
  • MPEG Systems further enhanced the ISOBMFF Standard
  • MPEG Video Coding completes Conformance and Reference Software for LCEVC
  • MPEG Video Coding issues Committee Draft of Conformance and Reference Software for MPEG Immersive Video
  • JVET produces Second Editions of VVC & VSEI and finalizes VVC Reference Software
  • JVET promotes Tenth Edition of AVC to Final Draft International Standard
  • JVET extends HEVC for High-Capability Applications up to 16K and Beyond
  • MPEG Genomic Coding evaluated Responses on New Advanced Genomics Features and Technologies
  • MPEG White Papers
    • Neural Network Coding (NNC)
    • Low Complexity Enhancement Video Coding (LCEVC)
    • MPEG Immersive video

In this column, I’d like to focus on the Emmy® Awards, video coding updates (AVC, HEVC, VVC, and beyond), and a brief update about DASH (as usual).

MPEG Systems Wins Two More Technology & Engineering Emmy® Awards

MPEG Systems is pleased to report that MPEG is being recognized this year by the National Academy for Television Arts and Sciences (NATAS) with two Technology & Engineering Emmy® Awards, for (i) “standardization of font technology for custom downloadable fonts and typography for Web and TV devices and for (ii) “standardization of HTTP encapsulated protocols”, respectively.

The first of these Emmys is related to MPEG’s Open Font Format (ISO/IEC 14496-22) and the second of these Emmys is related to MPEG Dynamic Adaptive Streaming over HTTP (i.e., MPEG DASH, ISO/IEC 23009). The MPEG DASH standard is the only commercially deployed international standard technology for media streaming over HTTP and it is widely used in many products. MPEG developed the first edition of the DASH standard in 2012 in collaboration with 3GPP and since then has produced four more editions amending the core specification by adding new features and extended functionality. Furthermore, MPEG has developed six other standards as additional “parts” of ISO/IEC 23009 enabling the effective use of the MPEG DASH standards with reference software and conformance testing tools, guidelines, and enhancements for additional deployment scenarios. MPEG DASH has dramatically changed the streaming industry by providing a standard that is widely adopted by various consortia such as 3GPP, ATSC, DVB, and HbbTV, and across different sectors. The success of this standard is due to its technical excellence, large participation of the industry in its development, addressing the market needs, and working with all sectors of industry all under ISO/IEC JTC 1/SC 29 MPEG Systems’ standard development practices and leadership.

These are MPEG’s fifth and sixth Technology & Engineering Emmy® Awards (after MPEG-1 and MPEG-2 together with JPEG in 1996, Advanced Video Coding (AVC) in 2008, MPEG-2 Transport Stream in 2013, and ISO Base Media File Format in 2021) and MPEG’s seventh and eighth overall Emmy® Awards (including the Primetime Engineering Emmy® Awards for Advanced Video Coding (AVC) High Profile in 2008 and High-Efficiency Video Coding (HEVC) in 2017).

I have been actively contributing to the MPEG DASH standard since its inception. My initial blog post dates back to 2010 and the first edition of MPEG DASH was published in 2012. A more detailed MPEG DASH timeline provides many pointers to the Institute of Information Technology (ITEC) at the Alpen-Adria-Universität Klagenfurt and its DASH activities that is now continued within the Christian Doppler Laboratory ATHENA. In the end, the MPEG DASH community of contributors to and users of the standards can be very proud of this achievement only after 10 years of the first edition being published. Thus, also happy 10th birthday MPEG DASH and what a nice birthday gift.

Video Coding Updates

In terms of video coding, there have been many updates across various standards’ projects at the 137th MPEG Meeting.

Advanced Video Coding

Starting with Advanced Video Coding (AVC), the 10th edition of Advanced Video Coding (AVC, ISO/IEC 14496-10 | ITU-T H.264) has been promoted to Final Draft International Standard (FDIS) which is the final stage of the standardization process. Beyond various text improvements, this specifies a new SEI message for describing the shutter interval applied during video capture. This can be variable in video cameras, and conveying this information can be valuable for analysis and post-processing of the decoded video.

High-Efficiency Video Coding

The High-Efficiency Video Coding (HEVC, ISO/IEC 23008-2 | ITU-T H.265) standard has been extended to support high-capability applications. It defines new levels and tiers providing support for very high bit rates and video resolutions up to 16K, as well as defining an unconstrained level. This will enable the usage of HEVC in new application domains, including professional, scientific, and medical video sectors.

Versatile Video Coding

The second editions of Versatile Video Coding (VVC, ISO/IEC 23090-3 | ITU-T H.266) and Versatile supplemental enhancement information messages for coded video bitstreams (VSEI, ISO/IEC 23002-7 | ITU-T H.274) have reached FDIS status. The new VVC version defines profiles and levels supporting larger bit depths (up to 16 bits), including some low-level coding tool modifications to obtain improved compression efficiency with high bit-depth video at high bit rates. VSEI version 2 adds SEI messages giving additional support for scalability, multi-view, display adaptation, improved stream access, and other use cases. Furthermore, a Committee Draft Amendment (CDAM) for the next amendment of VVC was issued to begin the formal approval process to enable linking VVC with the Green Metadata (ISO/IEC 23001-11) and Video Decoding Interface (ISO/IEC 23090-13) standards and add a new unconstrained level for exceptionally high capability applications such as certain uses in professional, scientific, and medical application scenarios. Finally, the reference software package for VVC (ISO/IEC 23090-16) was also completed with its achievement of FDIS status. Reference software is extremely helpful for developers of VVC devices, helping them in testing their implementations for conformance to the video coding specification.

Beyond VVC

The activities in terms of video coding beyond VVC capabilities, the Enhanced Compression Model (ECM 3.1) performance over VTM-11.0 + JVET-V0056 (i.e., VVC reference software) shows an improvement of close to 15% for Random Access Main 10. This is indeed encouraging and, in general, these activities are currently managed within two exploration experiments (EEs). The first is on neural network-based (NN) video coding technology (EE1) and the second is on enhanced compression beyond VVC capability (EE2). EE1 currently plans to further investigate (i) enhancement filters (loop and post) and (ii) super-resolution (JVET-Y2023). It will further investigate selected NN technologies on top of ECM 4 and the implementation of selected NN technologies in the software library, for platform-independent cross-checking and integerization. Enhanced Compression Model 4 (ECM 4) comprises new elements on MRL for intra, various GPM/affine/MV-coding improvements including TM, adaptive intra MTS, coefficient sign prediction, CCSAO improvements, bug fixes, and encoder improvements (JVET-Y2025). EE2 will investigate intra prediction improvements, inter prediction improvements, improved screen content tools, and improved entropy coding (JVET-Y2024).

Research aspects: video coding performance is usually assessed in terms of compression efficiency or/and encoding runtime (time complexity). Another aspect is related to visual quality, its assessment, and metrics, specifically for neural network-based video coding technologies.

The latest MPEG-DASH Update

Finally, I’d like to provide a brief update on MPEG-DASH! At the 137th MPEG meeting, MPEG Systems issued a draft amendment to the core MPEG-DASH specification (i.e., ISO/IEC 23009-1) about Extended Dependent Random Access Point (EDRAP) streaming and other extensions which it will be further discussed during the Ad-hoc Group (AhG) period (please join the dash email list for further details/announcements). Furthermore, Defects under Investigation (DuI) and Technologies under Consideration (TuC) are available here.

An updated overview of DASH standards/features can be found in the Figure below.

MPEG-DASH status of January 2021.

Research aspects: in the Christian Doppler Laboratory ATHENA we aim to research and develop novel paradigms, approaches, (prototype) tools and evaluation results for the phases (i) multimedia content provisioning (i.e., video coding), (ii) content delivery (i.e., video networking), and (iii) content consumption (i.e., video player incl. ABR and QoE) in the media delivery chain as well as for (iv) end-to-end aspects, with a focus on, but not being limited to, HTTP Adaptive Streaming (HAS).

The 138th MPEG meeting will be again an online meeting in July 2022. Click here for more information about MPEG meetings and their developments.

Towards an updated understanding of immersive multimedia experiences

Bringing theories and measurement techniques up to date

Development of technology for immersive multimedia experiences

Immersive multimedia experiences, as its name is suggesting are those experiences focusing on media that is able to immerse users with different interactions into an experience of an environment. Through different technologies and approaches, immersive media is emulating a physical world through the means of a digital or simulated world, with the goal of creating a sense of immersion. Users are involved in a technologically driven environment where they may actively join and participate in the experiences offered by the generated world [White Paper, 2020]. Currently, as hardware and technologies are developing further, those immersive experiences are getting better with the more advanced feeling of immersion. This means that immersive multimedia experiences are exceeding just the viewing of the screen and are enabling bigger potential. This column aims to present and discuss the need for an up to date understanding of immersive media quality. Firstly, the development of the constructs of immersion and presence over time will be outlined. Second, influencing factors of immersive media quality will be introduced, and related standardisation activities will be discussed. Finally, this column will be concluded by summarising why an updated understanding of immersive media quality is urgent.

Development of theories covering immersion and presence

One of the first definitions of presence was established by Slater and Usoh already in 1993 and they defined presence as a “sense of presence” in a virtual environment [Slater, 1993]. This is in line with other early definitions of presence and immersion. For example, Biocca defined immersion as a system property. Those definitions focused more on the ability of the system to technically accurately provide stimuli to users [Biocca, 1995]. As technology was only slowly capable to provide systems that are able to generate stimulation to users that can mimic the real world, this was of course the main content of definitions. Quite early on questionnaires to capture the experienced immersion were introduced, such as the Igroup Presence Questionnaire (IPQ) [Schubert, 2001]. Also, the early methods for measuring experiences are mainly focused on aspects of how good the representation of the real world was done and perceived. With maturing technology, the focus was shifted more towards emotions and more cognitive phenomena besides the basics stimulus generation. For example, Baños and colleagues showed that experienced emotion and immersion are in relation to each other and also influence the sense of presence [Baños, 2004]. Newer definitions focus more on these mentioned cognitive aspects, e.g., Nilsson defines three factors that can lead to immersion: (i) technology, (ii) narratives, and (iii) challenges, where only the factor technology is a non-cognitive one [Nilsson, 2016]. In 2018, Slater defines the place illusion as the illusion of being in a place while knowing one is not really there. This is a focus on a cognitive construct, removal of disbelieve, but still leaves the focus of how the illusion is created mainly on system factors instead of cognitive ones [Slater, 2018]. In recent years, more and more activities were started to define how to measure immersive experiences as an overall construct.

Constructs of interest in relation to immersion and presence

This section discusses constructs and activities that are related to immersion and presence. In the beginning, subtypes of extended reality (XR) and the relation to user experience (UX) as well as quality of experience (QoE) are outlined. Afterwards, recent standardization activities related to immersive multimedia experiences are introduced and discussed.
Moreover, immersive multimedia experiences can be divided by many different factors, but recently the most common distinctions are regarding the interactivity where content can be made for multi-directional viewing as 360-degree videos, or where content is presented through interactive extended reality. Those XR technologies can be divided into mixed reality (MR), augmented reality (AR), augmented virtuality (AV), virtual reality (VR), and everything in between [Milgram, 1995]. Through all those areas immersive multimedia experiences have found a place on the market, and are providing new solutions to challenges in research as well as in industries, with a growing potential of adopting into different areas [Chuah, 2018].

While discussing immersive multimedia experiences, it is important to address user experience and quality of immersive multimedia experiences, which can be defined following the definition of quality of experience itself [White Paper, 2012] as a measure of the delight or annoyance of a customer’s experiences with a service, wherein this case service is an immersive multimedia experience. Furthermore, while defining QoE terms experience and application are also defined and can be utilized for immersive multimedia experience, where an experience is an individual’s stream of perception and interpretation of one or multiple events; and application is a software and/or hardware that enables usage and interaction by a user for a given purpose [White Paper 2012].

As already mentioned, immersive media experiences have an impact in many different fields, but one, where the impact of immersion and presence is particularly investigated, is gaming applications along with QoE models and optimizations that go with it. Specifically interesting is the framework and standardization for subjective evaluation methods for gaming quality [ITU-T Rec. P.809, 2018]. This standardization is providing instructions on how to assess QoE for gaming services from two possible test paradigms, i.e., passive viewing tests and interactive tests. However, even though detailed information about the environments, test set-ups, questionnaires, and game selection materials are available those are still focused on the gaming field and concepts of flow and immersion in games themselves.

Together with gaming, another step in defining and standardizing infrastructure of audiovisual services in telepresence, immersive environments, and virtual and extended reality, has been done in regards to defining different service scenarios of immersive live experience [ITU-T Rec. H.430.3, 2018] where live sports, entertainment, and telepresence scenarios have been described. With this standardization, some different immersive live experience scenarios have been described together with architectural frameworks for delivering such services, but not covering all possible use case examples. When mentioning immersive multimedia experience, spatial audio sometimes referred to as “immersive audio” must be mentioned as is one of the key features of especially of AR or VR experiences [Agrawal, 2019], because in AR experiences it can provide immersive experiences on its own, but also enhance VR visual information.
In order to be able to correctly assess QoE or UX, one must be aware of all characteristics such as user, system, content, and context because their actual state may have an influence on the immersive multimedia experience of the user. That is why all those characteristics are defined as influencing factors (IF) and can be divided into Human IF, System IF, and Context IF and are as well standardized for virtual reality services [ITU-T Rec. G.1035, 2021]. Particularly addressed Human IF is simulator sickness as it specifically occurs as a result of exposure to immersive XR environments. Simulator sickness is also known as cybersickness or VR/AR sickness, as it is visually induced motion sickness triggered by visual stimuli and caused by the sensory conflict arising between the vestibular and visual systems. Therefore, to achieve the full potential of immersive multimedia experience, the unwanted sensation of simulation sickness must be reduced. However, with the frequent change of immersive technology, some hardware improvement is leading to better experiences, but a constant updating of requirement specification, design, and development is needed together with it to keep up with the best practices.

Conclusion – Towards an updated understanding

Considering the development of theories, definitions, and influencing factors around the constructs immersion and presence, one can see two different streams. First, there is a quite strong focus on the technical ability of systems in most early theories. Second, the cognitive aspects and non-technical influencing factors gain importance in the new works. Of course, it is clear that in the 1990ies, technology was not yet ready to provide a good simulation of the real world. Therefore, most activities to improve systems were focused on that activity including measurements techniques. In the last few years, technology was fast developing and the basic simulation of a virtual environment is now possible also on mobile devices such as the Oculus Quest 2. Although concepts such as immersion or presence are applicable from the past, definitions dealing with those concepts need to capture as well nowadays technology. Meanwhile, systems have proven to provide good real-world simulators and provide users with a feeling of presence and immersion. While there is already activity in standardization which is quite strong and also industry-driven, research in many research disciplines such as telecommunication are still mainly using old questionnaires. These questionnaires are mostly focused on technological/real-world simulation constructs and, thus, not able to differentiate products and services anymore to an extent that is optimal. There are some newer attempts to create new measurement tools for e.g. social aspects of immersive systems [Li, 2019; Toet, 2021]. Measurement scales aiming at capturing differences due to the ability of systems to create realistic simulations are not able to reliably differentiate different systems due to the fact that most systems are providing realistic real-world simulations. To enhance research and industrial development in the field of immersive media, we need definitions of constructs and measurement methods that are appropriate for the current technology even if the newer measurement and definitions are not as often cited/used yet. That will lead to improved development and in the future better immersive media experiences.

One step towards understanding immersive multimedia experiences is reflected by QoMEX 2022. The 14th International Conference on Quality of Multimedia Experience will be held from September 5th to 7th, 2022 in Lippstadt, Germany. It will bring together leading experts from academia and industry to present and discuss current and future research on multimedia quality, Quality of Experience (QoE), and User Experience (UX). It will contribute to excellence in developing multimedia technology towards user well-being and foster the exchange between multidisciplinary communities. One core topic is immersive experiences and technologies as well as new assessment and evaluation methods, and both topics contribute to bringing theories and measurement techniques up to date. For more details, please visit https://qomex2022.itec.aau.at.

References

[Agrawal, 2019] Agrawal, S., Simon, A., Bech, S., Bærentsen, K., Forchhammer, S. (2019). “Defining Immersion: Literature Review and Implications for Research on Immersive Audiovisual Experiences.” In Audio Engineering Society Convention 147. Audio Engineering Society.
[Biocca, 1995] Biocca, F., & Delaney, B. (1995). Immersive virtual reality technology. Communication in the age of virtual reality, 15(32), 10-5555.
[Baños, 2004] Baños, R. M., Botella, C., Alcañiz, M., Liaño, V., Guerrero, B., & Rey, B. (2004). Immersion and emotion: their impact on the sense of presence. Cyberpsychology & behavior, 7(6), 734-741.
[Chuah, 2018] Chuah, S. H. W. (2018). Why and who will adopt extended reality technology? Literature review, synthesis, and future research agenda. Literature Review, Synthesis, and Future Research Agenda (December 13, 2018).
[ITU-T Rec. G.1035, 2021] ITU-T Recommendation G:1035 (2021). Influencing factors on quality of experience for virtual reality services, Int. Telecomm. Union, CH-Geneva.
[ITU-T Rec. H.430.3, 2018] ITU-T Recommendation H:430.3 (2018). Service scenario of immersive live experience (ILE), Int. Telecomm. Union, CH-Geneva.
[ITU-T Rec. P.809, 2018] ITU-T Recommendation P:809 (2018). Subjective evaluation methods for gaming quality, Int. Telecomm. Union, CH-Geneva.
[Li, 2019] Li, J., Kong, Y., Röggla, T., De Simone, F., Ananthanarayan, S., De Ridder, H., … & Cesar, P. (2019, May). Measuring and understanding photo sharing experiences in social Virtual Reality. In Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems (pp. 1-14).
[Milgram, 1995] Milgram, P., Takemura, H., Utsumi, A., & Kishino, F. (1995, December). Augmented reality: A class of displays on the reality-virtuality continuum. In Telemanipulator and telepresence technologies (Vol. 2351, pp. 282-292). International Society for Optics and Photonics.
[Nilsson, 2016] Nilsson, N. C., Nordahl, R., & Serafin, S. (2016). Immersion revisited: a review of existing definitions of immersion and their relation to different theories of presence. Human Technology, 12(2).
[Schubert, 2001] Schubert, T., Friedmann, F., & Regenbrecht, H. (2001). The experience of presence: Factor analytic insights. Presence: Teleoperators & Virtual Environments, 10(3), 266-281.
[Slater, 1993] Slater, M., & Usoh, M. (1993). Representations systems, perceptual position, and presence in immersive virtual environments. Presence: Teleoperators & Virtual Environments, 2(3), 221-233.
[Toet, 2021] Toet, A., Mioch, T., Gunkel, S. N., Niamut, O., & van Erp, J. B. (2021). Holistic Framework for Quality Assessment of Mediated Social Communication.
[Slater, 2018] Slater, M. (2018). Immersion and the illusion of presence in virtual reality. British Journal of Psychology, 109(3), 431-433.
[White Paper, 2012] Qualinet White Paper on Definitions of Quality of Experience (2012). European Network on Quality of Experience in Multimedia Systems and Services (COST Action IC 1003), Patrick Le Callet, Sebastian Möller and Andrew Perkis, eds., Lausanne, Switzerland, Version 1.2, March 2013.
[White Paper, 2020] Perkis, A., Timmerer, C., Baraković, S., Husić, J. B., Bech, S., Bosse, S., … & Zadtootaghaj, S. (2020). QUALINET white paper on definitions of immersive media experience (IMEx). arXiv preprint arXiv:2007.07032.

MPEG Column: 135th MPEG Meeting (virtual/online)

The original blog post can be found at the Bitmovin Techblog and has been modified/updated here to focus on and highlight research aspects.

The 135th MPEG meeting was once again held as an online meeting, and the official press release can be found here and comprises the following items:

  • MPEG Video Coding promotes MPEG Immersive Video (MIV) to the FDIS stage
  • Verification tests for more application cases of Versatile Video Coding (VVC)
  • MPEG Systems reaches first milestone for Video Decoding Interface for Immersive Media
  • MPEG Systems further enhances the extensibility and flexibility of Network-based Media Processing
  • MPEG Systems completes support of Versatile Video Coding and Essential Video Coding in High Efficiency Image File Format
  • Two MPEG White Papers:
    • Versatile Video Coding (VVC)
    • MPEG-G and its application of regulation and privacy

In this column, I’d like to focus on MIV and VVC including systems-related aspects as well as a brief update about DASH (as usual).

MPEG Immersive Video (MIV)

At the 135th MPEG meeting, MPEG Video Coding has promoted the MPEG Immersive Video (MIV) standard to the Final Draft International Standard (FDIS) stage. MIV was developed to support compression of immersive video content in which multiple real or virtual cameras capture a real or virtual 3D scene. The standard enables storage and distribution of immersive video content over existing and future networks for playback with 6 Degrees of Freedom (6DoF) of view position and orientation.

From a technical point of view, MIV is a flexible standard for multiview video with depth (MVD) that leverages the strong hardware support for commonly used video codecs to code volumetric video. The actual views may choose from three projection formats: (i) equirectangular, (ii) perspective, or (iii) orthographic. By packing and pruning views, MIV can achieve bit rates around 25 Mb/s and a pixel rate equivalent to HEVC Level 5.2.

The MIV standard is designed as a set of extensions and profile restrictions for the Visual Volumetric Video-based Coding (V3C) standard (ISO/IEC 23090-5). The main body of this standard is shared between MIV and the Video-based Point Cloud Coding (V-PCC) standard (ISO/IEC 23090-5 Annex H). It may potentially be used by other MPEG-I volumetric codecs under development. The carriage of MIV is specified through the Carriage of V3C Data standard (ISO/IEC 23090-10).

The test model and objective metrics are publicly available at https://gitlab.com/mpeg-i-visual.

At the same time, MPEG Systems has begun developing the Video Decoding Interface for Immersive Media (VDI) standard (ISO/IEC 23090-13) for a video decoders’ input and output interfaces to provide more flexible use of the video decoder resources for such applications. At the 135th MPEG meeting, MPEG Systems has reached the first formal milestone of developing the ISO/IEC 23090-13 standard by promoting the text to Committee Draft ballot status. The VDI standard allows for dynamic adaptation of video bitstreams to provide the decoded output pictures in such a way so that the number of actual video decoders can be smaller than the number of the elementary video streams to be decoded. In other cases, virtual instances of video decoders can be associated with the portions of elementary streams required to be decoded. With this standard, the resource requirements of a platform running multiple virtual video decoder instances can be further optimized by considering the specific decoded video regions that are to be actually presented to the users rather than considering only the number of video elementary streams in use.

Research aspects: It seems that visual compression and systems standards enabling immersive media applications and services are becoming mature. However, the Quality of Experience (QoE) of such applications and services is still in its infancy. The QUALINET White Paper on Definitions of Immersive Media Experience (IMEx) provides a survey of definitions of immersion and presence which leads to a definition of Immersive Media Experience (IMEx). Consequently, the next step is working towards QoE metrics in this domain that requires subjective quality assessments imposing various challenges during the current COVID-19 pandemic.

Versatile Video Coding (VVC) updates

The third round of verification testing for Versatile Video Coding (VVC) has been completed. This includes the testing of High Dynamic Range (HDR) content of 4K ultra-high-definition (UHD) resolution using the Hybrid Log-Gamma (HLG) and Perceptual Quantization (PQ) video formats. The test was conducted using state-of-the-art high-quality consumer displays, emulating an internet streaming-type scenario.

On average, VVC showed on average approximately 50% bit rate reduction compared to High Efficiency Video Coding (HEVC).

Additionally, the ISO/IEC 23008-12 Image File Format has been amended to support images coded using Versatile Video Coding (VVC) and Essential Video Coding (EVC).

Research aspects: The results of the verification tests are usually publicly available and can be used as a baseline for future improvements of the respective standards including the evaluation thereof. For example, the tradeoff compression efficiency vs. encoding runtime (time complexity) for live and video on-demand scenarios is always an interesting research aspect.

The latest MPEG-DASH Update

Finally, I’d like to provide a brief update on MPEG-DASH! At the 135th MPEG meeting, MPEG Systems issued a draft amendment to the core MPEG-DASH specification (i.e., ISO/IEC 23009-1) that provides further improvements of Preroll which is renamed to Preperiod and it will be further discussed during the Ad-hoc Group (AhG) period (please join the dash email list for further details/announcements). Additionally, this amendment includes some minor improvements for nonlinear playback. The so-called Technologies under Consideration (TuC) document comprises new proposals that did not yet reach consensus for promotion to any official standards documents (e.g., amendments to existing DASH standards or new parts). Currently, proposals for minimizing initial delay are discussed among others. Finally, libdash has been updated to support the MPEG-DASH schema according to the 5th edition.

An updated overview of DASH standards/features can be found in the Figure below.

MPEG-DASH status of July 2021.

Research aspects: The informative aspects of MPEG-DASH such as the adaptive bitrate (ABR) algorithms have been subject to research for many years. New editions of the standard mostly introduced incremental improvements but disruptive ideas rarely reached the surface. Perhaps it’s time to take a step back and re-think how streaming should work for todays and future media applications and services.

The 136th MPEG meeting will be again an online meeting in October 2021 but MPEG is aiming to meet in-person again in January 2021 (if possible). Click here for more information about MPEG meetings and their developments.

MPEG Visual Quality Assessment Advisory Group: Overview and Perspectives

Introduction

The perceived visual quality is of utmost importance in the context of visual media compression, such as 2D, 3D, immersive video, and point clouds. The trade-off between compression efficiency and computational/implementation complexity has a crucial impact on the success of a compression scheme. This specifically holds for the development of visual media compression standards which typically aims at maximum compression efficiency using state-of-the-art coding technology. In MPEG, the subjective and objective assessment of visual quality has always been an integral part of the standards development process. Due to the significant effort of formal subjective evaluations, the standardization process typically relies on such formal tests in the starting phase and for verification while in the development phase objective metrics are used. In the new MPEG structure, established in 2020, a dedicated advisory group has been installed for the purpose of providing, maintaining, and developing visual quality assessment methods suitable for use in the standardization process.

This column lays out the scope and tasks of this advisory group and reports on its first achievements and developments. After a brief overview of the organizational structure, current projects are presented, and initial results are presented.

Organizational Structure

MPEG: A Group of Groups in ISO/IEC JTC 1/SC 29

The Moving Pictures Experts Groups (MPEG) is a standardization group that develops standards for coded representation of digital audio, video, 3D Graphics and genomic data. Since its establishment in 1988, the group has produced standards that enable the industry to offer interoperable devices for an enhanced digital media experience [1]. In its new structure as defined in 2020, MPEG is established as a set of Working Groups (WGs) and Advisory Groups (AGs) in Sub-Committee (SC) 29 “Coding of audio, picture, multimedia and hypermedia information” of the Joint Technical Committee (JTC) 1 of ISO (International Standardization Organization) and IEC (International Electrotechnical Commission). The lists of WGs and AGs in SC 29 are shown in Figure 1. Besides MPEG, SC 29 also includes and JPEG (the Joint Photographic Experts Group, WG 1) as well as an Advisory Group for Chair Support Team and Management (AG 1) and an Advisory Group for JPEG and MPEG Collaboration (AG 4), thereby covering the wide field of media compression and transmission. Within this structure, the focus of AG 5 MPEG Visual Quality Assessment (MPEG VQA) is on interaction and collaboration with the working groups directly working on MPEG visual media compression, including WG 4 (Video Coding), WG 5 (JVET), and WG 7 (3D Graphics).

Figure 1. MPEG Advisory Groups (AGs) and Working Groups (WGs) in ISO/IEC JTC 1/SC 29 [2].

Setting the Field for MPEG VQA: The Terms of Reference

SC 29 has defined Terms of Reference (ToR) for all its WGs and AGs. The scope of AG5 MPEG Visual Quality Assessment is to support needs for quality assessment testing in close coordination with the relevant MPEG Working Groups, dealing with visual quality, with the following activities [2]:

  • to assess the visual quality of new technologies to be considered to begin a new standardization project;
  • to contribute to the definition of Calls for Proposals (CfPs) for new standardization work items;
  • to select and design subjective quality evaluation methodologies and objective quality metrics for the assessment of visual coding technologies, e.g., in the context of a Call for Evidence (CfE) and CfP;
  • to contribute to the selection of test material and coding conditions for a CfP;
  • to define the procedures useful to assess the visual quality of the submissions to a CfP;
  • to design and conduct visual quality tests, process, and analyze the raw data, and make the report of the evaluation results available conclusively;
  • to support in the assessment of the final status of a standard, verifying its performance compared to the existing standard(s);
  • to maintain databases of test material;
  • to recommend guidelines for selection of testing laboratories (verifying their current capabilities);
  • to liaise with ITU and other relevant organizations on the creation of new Quality Assessment standards or the improvement of the existing ones.

Way of Working

Given the fact that MPEG Visual Quality Assessment is an advisory group, and given the above-mentioned ToR, the goal of AG5 is not to produce new standards on its own. Instead, AG5 strives to communicate and collaborate with relevant SDOs in the field, applying existing standards and recommendations and potentially contributing to further development by reporting results and working practices to these groups.

In terms of meetings, AG5 adopts the common MPEG meeting cycle of typically four MPEG AG/WG meetings per year, which -due to the ongoing pandemic situation- so far have all been held online. The meetings are held to review the progress of work, agree on recommendations, and decide on further plans. During the meeting, AG5 closely collaborates with the MPEG WGs and conducts experts viewing sessions in various MPEG standardization activities. The focus of such activities includes the preparation of new standardization projects, the performance verification of completed projects, as well as support of ongoing projects, where frequent subjective evaluation results are required in the decision process. Between meetings, AG5 work is carried out in the context of Ad-hoc Groups (AhGs) which are established from meeting to meeting with well-defined tasks.

Focus Groups

Due to the broad field of ongoing standardization activities, AG5 has established so-called focus groups which cover the relevant fields of development. The focus group structure and the appointed chairs are shown in Figure 2.

Figure 2. MPEG VQA focus groups.

The focus groups are mandated to coordinate with other relevant MPEG groups and other standardization bodies on activities of mutual interest, and to facilitate the formal and informal assessment of the visual media type under their consideration. The focus groups are described as follows:

  • Standard Dynamic Range Video (SDR): This is the ‘classical’ video quality assessment domain. The group strives to support, design, and conduct testing activities on SDR content at any resolution and coding condition, and to maintain existing testing methods and best practice procedures.
  • High Dynamic Range Video (HDR): The focus group on HDR strives to facilitate the assessment of HDR video quality using different devices with combinations of spatial resolution, colour gamut, and dynamic range, and further to maintain and refine methodologies for measuring HDR video quality. A specific focus of the starting phase was on the preparation of the verification tests for Versatile Video Coding (VVC, ISO/IEC 23090-3 / ITU-T H.266).
  • 360° Video: The omnidirectional characteristics of 360° video content have to be taken into account for visual quality assessment. The groups’ focus is on continuing the development of 360° video quality assessment methodologies, including those using head-mounted devices. Like with the focus group on HDR, the verification tests for VVC had priority in the starting phase.
  • Immersive Video (MPEG Immersive Video, MIV): Since MIV allows for movement of the user at six degrees of freedom, the assessment of this type of content bears even more challenges and the variability of the user’s perception of the media has to be factored in. Given the absence of an original reference or ground truth, for the synthetically rendered scene, objective evaluation with conventional objective metrics is a challenge. The focus group strives to develop appropriate subjective expert viewing methods to support the development process of the standard and also evaluates and improve objective metrics in the context of MIV.

Ad hoc Groups

AG5 currently has three AhGs defined which are briefly presented with their mandates below:

  • Quality of immersive visual media (chaired by Christian Timmerer of AAU/Bitmovin, Joel Jung of Tencent, and Aljosa Smolic of Trinity College Dublin): Study Draft Overview of Quality Metrics and Methodologies for Immersive Visual Media (AG 05/N00013) with respect to new updates presented at this meeting; Solicit inputs for subjective evaluation methods and objective metrics for immersive video (e.g., 360, MIV, V-PCC, G-PCC); Organize public online workshop(s) on Quality of Immersive Media: Assessment and Metrics.
  • Learning-based quality metrics for 2D video (chaired by Yan Ye of Alibaba and Mathias Wien of RWTH Aachen University): Compile and maintain a list of video databases suitable and available to be used in AG5’s studies; Compile a list of learning-based quality metrics for 2D video to be studied; Evaluate the correlation between the learning-based quality metrics and subjective quality scores in the databases;
  • Guidelines for subjective visual quality evaluation (chaired by Mathias Wien of RWTH Aachen University, Lu Yu of Zhejiang University and Convenor of MPEG Video Coding (ISO/IEC JTC1 SC29/WG4), and Joel Jung of Tencent): Prepare the third draft of the Guidelines for Verification Testing of Visual Media Specifications; Prepare the second draft of the Guidelines for remote experts viewing test methods for use in the context of Ad-hoc Groups, and Core or Exploration Experiments.

AG 5 First Achievements

Reports and Guidelines

The results of the work of the AhGs are aggregated in AG5 output documents which are public (or will become public soon) in order to allow for feedback also from outside of the MPEG community.

The AhG on “Quality for Immersive Visual Media” maintains a report “Overview of Quality Metrics and Methodologies for Immersive Visual Media” [3] which documents the state-of-the-art in the field and shall serve as a reference for MPEG working groups in their work on compression standards in this domain. The AhG further organizes a public workshop on “Quality of Immersive Media: Assessment and Metrics” which takes place in an online form at the beginning of October 2021 [4]. The scope of this workshop is to raise awareness about MPEG efforts in the context of quality of immersive visual media and to invite experts outside of MPEG to present new techniques relevant to the scope of this workshop.

The AhG on “Guidelines for Subjective Visual Quality Evaluation” currently develops two guideline documents supporting the MPEG standardization work. The “Guidelines for Verification Testing of Visual Media Specifications” [5] define the process of assessing the performance of a completed standard after its publication. The concept of verification testing has already been established MPEG working practice for its media compression standards since the 1990ties. The document is intended to formalize the process, describe the steps and conditions for the verification tests, and set the requirements to meet MPEG procedural quality expectations.

The AhG has further released a first draft of “Guidelines for Remote Experts Viewing Sessions” with the intention to establish a formalized procedure for ad-hoc generation subjective test results as input to the standards development process [6]. This activity has been driven by the ongoing pandemic situation which forced MPEG to continue its work in virtual online meetings since early 2020. The procedure for remote experts viewing is intended to be applied during the (online) meeting phase or in the AhG phase and to provide measurable and reproducible subjective results in order to be input to the decision-making process in the project under consideration.

Verification Testing

With Essential Video Coding (EVC) [7], Low Complexity Enhancement Video Coding (LCEVC) [8] of ISO/IEC, and the joint coding standard Versatile Video Coding (VVC) of ISO/IEC and ITU-T [9][10], a significant number of new video coding standards has been recently released. Since its first meeting in October 2020, AG5 has been engaged in the preparation and conduction of verification tests for these video coding specifications. Further verification tests for MPEG Immersive Video (MIV) and Video-based Point Cloud Compression (V-PCC) [11] are under preparation and more are to come. Results of the verification test activities which have been completed in the first year of AG5 are summarized in the following subsections. All reported results have been achieved by formal subjective assessments according to established assessment protocols [12][13] and performed by qualified test laboratories. The bitstreams were generated with reference software encoders of the specification under consideration using established encoder configurations with comparable settings for both, the reference and the evaluated coding schemes. It has to be noted that all testing had to be done under the constrained conditions of the ongoing pandemic situation which induced an additional challenge for the test laboratories in charge.

MPEG-5 Part 1: Essential Video Coding (EVC)

The EVC standard was developed with the goal to provide a royalty-free Baseline profile and a Main profile with higher compression efficiency compared to High-Efficiency Video Coding (HEVC) [15][16][17]. Verification tests were conducted for Standard Dynamic Range (SDR) and high dynamic range (HDR, BT.2100 PQ) video content at both, HD (1920×1080 pixels) and UHD (3840×2160 pixels) resolution. The tests revealed around 40% bitrate savings at a comparable visual quality for the Main profile when compared to HEVC, and around 36% bitrate saving for the Baseline profile when compared to Advanced Video Coding (AVC) [18][19], both for SDR content [20]. For HDR PQ content, the Main profile provided around 35% bitrate savings for both resolutions [21].

MPEG-5 Part 2: Low-Complexity Enhancement Video Coding (LCEVC)

The LCEVC standard follows a layered approach where an LCEVC enhancement layer is added to a lower resolution base layer of an existing codec in order to achieve the full resolution video [22]. Since the base layer codec operates at a lower resolution and the separate enhancement layer decoding process is relatively lightweight, the computational complexity of the decoding process is typically lower compared to decoding of the full resolution with the base layer codec. The addition of the enhancement layer would typically be provided on top of the established base layer decoder implementation by an additional decoding entity, e.g., in a browser.

For verification testing, LCEVC was evaluated using AVC, HEVC, EVC, and VVC base layer bitstreams at half resolution, and comparing the performance to the respective schemes with full resolution coding as well half-resolution coding with a simple upsampling tool. For UHD resolution, the bitrate savings for LCEVC at comparable visual quality were at 46% when compared to full resolution AVC and 31% when compared to full resolution HEVC. The comparison to the more recent and more efficient EVC and VVC coding schemes led to partially overlapping confidence intervals of the subjective scores of the test subjects. The curves still revealed some benefits for the application of LCEVC. The gains compared to half-resolution coding with simple upsampling provided approximately 28%, 34%, 38%, and 33% bitrate savings at comparable visual quality, demonstrating the benefit of LCEVC enhancement layer coding compared to straight-forward plain upsampling [23].

MPEG-I Part 3 / ITU-T H.266: Versatile Video Coding (VVC)

VVC is the most recent video coding standard in the historical line of joint specifications of ISO/IEC and ITU-T, such as AVC and HEVC. The development focus for VVC was on compression efficiency improvement at a moderate increase of decode complexity as well as the versatility of the design [24][25]. Versatility features include tools designed to address HDR, WCG, resolution-adaptive multi-rate video streaming services, 360-degree immersive video, bitstream extraction and merging, temporal scalability, gradual decoding refresh, and multilayer coding to deliver layered video content to support application features such as multiview, alpha maps, depth maps, and spatial and quality scalability.

A series of verification tests have been conducted covering SDR UHD and HD, HDR PQ and HLG, as well as 360° video contents [26][27][28]. An early open-source encoder (VVenC, [14]) was additionally assessed in some categories. For SDR coding, both, the VVC reference software (VTM) and the open-source VVenC were evaluated against the HEVC reference software (HM). The results revealed bit rate savings of around 46% (SDR UHD, VTM and VVenC), 50% (SDR HD, VTM and VVenC), 49% (HDR UHD, PQ and HLG), 52%, and 50-56% (360° with different projection formats) at a similar visual quality compared to HEVC. In Figure 3, pooled MOS (Mean Opinion Score) over bit rate points for the mentioned categories are provided. The MOS values range from 10 (imperceptible impairments) down to 0 (everywhere severely annoying impairments). Pooling was done by computing the geometric mean of the bitrates and the arithmetic mean of the MOS scores across the test sequences of each test category. The results reveal a consistent benefit of VVC over its predecessor HEVC in terms of visual quality over the required bitrate.

Figure 3. Pooled MOS over bitrate plots of the VVC verification tests for the SDR UHD, SDR HD, HDR HLG, and 360° video test categories. Curves cited from [26][27][28].

Summary

This column presented an overview of the organizational structure and the activities of the Advisory Group on MPEG Visual Quality Assessment, ISO/IEC JTC 1/SC 29/AG 5, which has been formed about one year ago. The work items of AG5 include the application, documentation, evaluation, and improvement of objective quality metrics and subjective quality assessment procedures. In its first year of existence, the group has produced an overview on immersive quality metrics, draft guidelines for verification tests and for remote experts viewing sessions as well as reports of formal subjective quality assessments for the verification tests of EVC, LCEVC, and VVC. The work of the group will continue towards studying and developing quality metrics suitable for the assessment tasks emerging by the development of the various MPEG visual media coding standards and towards subjective quality evaluation in upcoming and future verification tests and new standardization projects.

References

[1] MPEG website, https://www.mpegstandards.org/.
[2] ISO/IEC JTC1 SC29, “Terms of Reference of SC 29/WGs and AGs,” Doc. SC29N19020, July 2020.
[3] ISO/IEC JTC1 SC29/AG5 MPEG VQA, “Draft Overview of Quality Metrics and Methodologies for Immersive Visual Media (v2)”, doc. AG5N13, 2nd meeting: January 2021.
[4] MPEG AG 5 Workshop on Quality of Immersive Media: Assessment and Metrics, https://multimediacommunication.blogspot.com/2021/08/mpeg-ag-5-workshop-on-quality-of.html, October 5th, 2021.
[5] ISO/IEC JTC1 SC29/AG5 MPEG VQA, “Guidelines for Verification Testing of Visual Media Specifications (draft 2)”, doc. AG5N30, 4th meeting: July 2021.
[6] ISO/IEC JTC1 SC29/AG5 MPEG VQA, “Guidelines for remote experts viewing sessions (draft 1)”, doc. AG5N31, 4th meeting: July 2021.
[7] ISO/IEC 23094-1:2020, “Information technology — General video coding — Part 1: Essential video coding”, October 2020.
[8] ISO/IEC 23094-2, “Information technology – General video coding — Part 2: Low complexity enhancement video coding”, September 2021.
[9] ISO/IEC 23090-3:2021, “Information technology — Coded representation of immersive media — Part 3: Versatile video coding”, February 2021.
[10] ITU-T H.266, “Versatile Video Coding“, August 2020. https://www.itu.int/rec/recommendation.asp?lang=en&parent=T-REC-H.266-202008-I.
[11] ISO/IEC 23090-5:2021, “Information technology — Coded representation of immersive media — Part 5: Visual volumetric video-based coding (V3C) and video-based point cloud compression (V-PCC)”, June 2021.
[12] ITU-T P.910 (2008), Subjective video quality assessment methods for multimedia applications.
[13] ITU-R BT.500-14 (2019), Methodologies for the subjective assessment of the quality of television images.
[14] Fraunhofer HHI VVenC software repository. [Online]. Available: https://github.com/fraunhoferhhi/vvenc.
[15] K. Choi, J. Chen, D. Rusanovskyy, K.-P. Choi and E. S. Jang, “An overview of the MPEG-5 essential video coding standard [standards in a nutshell]”, IEEE Signal Process. Mag., vol. 37, no. 3, pp. 160-167, May 2020.
[16] ISO/IEC 23008-2:2020, “Information technology — High efficiency coding and media delivery in heterogeneous environments — Part 2: High efficiency video coding”, August 2020.
[17] ITU-T H.265, “High Efficiency Video Coding”, August 2021.
[18] ISO/IEC 14496-10:2020, “Information technology — Coding of audio-visual objects — Part 10: Advanced video coding”, December 2020.
[19] ITU-T H.264, “Advanced Video Coding”, August 2021.
[20] ISO/IEC JTC1 SC29/WG4, “Report on Essential Video Coding compression performance verification testing for SDR Content”, doc WG4N47, 2nd meeting: January 2021.
[21] ISO/IEC JTC1 SC29/WG4, “Report on Essential Video Coding compression performance verification testing for HDR/WCG content”, doc WG4N30, 1st meeting: October 2020.
[22] G. Meardi et al., “MPEG-5—Part 2: Low complexity enhancement video coding (LCEVC): Overview and performance evaluation”, Proc. SPIE, vol. 11510, pp. 238-257, Aug. 2020.
[23] ISO/IEC JTC1 SC29/WG4, “Verification Test Report on the Compression Performance of Low Complexity Enhancement Video Coding”, doc. WG4N76, 3rd meeting: April 2020.
[24] Benjamin Bross, Jianle Chen, Jens-Rainer Ohm, Gary J. Sullivan, and Ye-Kui Wang, “Developments in International Video Coding Standardization After AVC, With an Overview of Versatile Video Coding (VVC)”, Proceedings of the IEEE, Vol. 109, Issue 9, pp. 1463–1493, doi 10.1109/JPROC.2020.3043399, Sept. 2021 (open access publication), available at https://ieeexplore.ieee.org/document/9328514.
[25] Benjamin Bross, Ye-Kui Wang, Yan Ye, Shan Liu, Gary J. Sullivan, and Jens-Rainer Ohm, “Overview of the Versatile Video Coding (VVC) Standard and its Applications”, IEEE Trans. Circuits & Systs. for Video Technol. (open access publication), available online at https://ieeexplore.ieee.org/document/9395142.
[26] Mathias Wien and Vittorio Baroncini, “VVC Verification Test Report for Ultra High Definition (UHD) Standard Dynamic Range (SDR) Video Content”, doc. JVET-T2020 of ITU-T/ISO/IEC Joint Video Experts Team (JVET), 20th meeting: October 2020.
[27] Mathias Wien and Vittorio Baroncini, “VVC Verification Test Report for High Definition (HD) and 360° Standard Dynamic Range (SDR) Video Content”, doc. JVET-V2020 of ITU-T/ISO/IEC Joint Video Experts Team (JVET), 22nd meeting: April 2021.
[28] Mathias Wien and Vittorio Baroncini, “VVC verification test report for high dynamic range video content”, doc. JVET-W2020 of ITU-T/ISO/IEC Joint Video Experts Team (JVET), 23rd meeting: July 2021.

MPEG Column: 134th MPEG Meeting (virtual/online)

The original blog post can be found at the Bitmovin Techblog and has been modified/updated here to focus on and highlight research aspects.

The 134th MPEG meeting was once again held as an online meeting, and the official press release can be found here and comprises the following items:

  • First International Standard on Neural Network Compression for Multimedia Applications
  • Completion of the carriage of VVC and EVC
  • Completion of the carriage of V3C in ISOBMFF
  • Call for Proposals: (a) new Advanced Genomics Features and Technologies, (b) MPEG-I Immersive Audio, and (c) coded Representation of Haptics
  • MPEG evaluated Responses on Incremental Compression of Neural Networks
  • Progression of MPEG 3D Audio Standards
  • The first milestone of development of Open Font Format (2nd amendment)
  • Verification tests: (a) low Complexity Enhancement Video Coding (LCEVC) Verification Test and (b) more application cases of Versatile Video Coding (VVC)
  • Standardization work on Version 2 of VVC and VSEI started

In this column, the focus is on streaming-related aspects including a brief update about MPEG-DASH.

First International Standard on Neural Network Compression for Multimedia Applications

Artificial neural networks have been adopted for a broad range of tasks in multimedia analysis and processing, such as visual and acoustic classification, extraction of multimedia descriptors, or image and video coding. The trained neural networks for these applications contain many parameters (i.e., weights), resulting in a considerable size. Thus, transferring them to several clients (e.g., mobile phones, smart cameras) benefits from a compressed representation of neural networks.

At the 134th MPEG meeting, MPEG Video ratified the first international standards on Neural Network Compression for Multimedia Applications (ISO/IEC 15938-17), designed as a toolbox of compression technologies. The specification contains different methods for

  • parameter reduction (e.g., pruning, sparsification, matrix decomposition),
  • parameter transformation (e.g., quantization), and
  • entropy coding 

methods that can be assembled to encoding pipelines combining one or more (in the case of reduction) methods from each group.

The results show that trained neural networks for many common multimedia problems such as image or audio classification or image compression can be compressed by a factor of 10-20 with no performance loss and even by more than 30 with performance trade-off. The specification is not limited to a particular neural network architecture and is independent of the neural network exchange format choice. The interoperability with common neural network exchange formats is described in the annexes of the standard.

As neural networks are becoming increasingly important, the communication thereof over heterogeneous networks to a plethora of devices raises various challenges including efficient compression that is inevitable and addressed in this standard. ISO/IEC 15938 is commonly referred to as MPEG-7 (or the “multimedia content description interface”) and this standard becomes now part 15 of MPEG-7.

Research aspects: Like for all compression-related standards, research aspects are related to compression efficiency (lossy/lossless), computational complexity (runtime, memory), and quality-related aspects. Furthermore, the compression of neural networks for multimedia applications probably enables new types of applications and services to be deployed in the (near) future. Finally, simultaneous delivery and consumption (i.e., streaming) of neural networks including incremental updates thereof will become a requirement for networked media applications and services.

Carriage of Media Assets

At the 134th MPEG meeting, MPEG Systems completed the carriage of various media assets in MPEG-2 Systems (Transport Stream) and the ISO Base Media File Format (ISOBMFF), respectively.

In particular, the standards for the carriage of Versatile Video Coding (VVC) and Essential Video Coding (EVC) over both MPEG-2 Transport Stream (M2TS) and ISO Base Media File Format (ISOBMFF) reached their final stages of standardization, respectively:

  • For M2TS, the standard defines constraints to elementary streams of VVC and EVC to carry them in the packetized elementary stream (PES) packets. Additionally, buffer management mechanisms and transport system target decoder (T-STD) model extension are also defined.
  • For ISOBMFF, the carriage of codec initialization information for VVC and EVC is defined in the standard. Additionally, it also defines samples and sub-samples reflecting the high-level bitstream structure and independently decodable units of both video codecs. For VVC, signaling and extraction of a certain operating point are also supported.

Finally, MPEG Systems completed the standard for the carriage of Visual Volumetric Video-based Coding (V3C) data using ISOBMFF. Therefore, it supports media comprising multiple independent component bitstreams and considers that only some portions of immersive media assets need to be rendered according to the users’ position and viewport. Thus, the metadata indicating the relationship between the region in the 3D spatial data to be rendered and its location in the bitstream is defined. In addition, the delivery of the ISOBMFF file containing a V3C content over DASH and MMT is also specified in this standard.

Research aspects: Carriage of VVC, EVC, and V3C using M2TS or ISOBMFF provides an essential building block within the so-called multimedia systems layer resulting in a plethora of research challenges as it typically offers an interoperable interface to the actual media assets. Thus, these standards enable efficient and flexible provisioning or/and use of these media assets that are deliberately not defined in these standards and subject to competition.

Call for Proposals and Verification Tests

At the 134th MPEG meeting, MPEG issued three Call for Proposals (CfPs) that are briefly highlighted in the following:

  • Coded Representation of Haptics: Haptics provide an additional layer of entertainment and sensory immersion beyond audio and visual media. This CfP aims to specify a coded representation of haptics data, e.g., to be carried using ISO Base Media File Format (ISOBMFF) files in the context of MPEG-DASH or other MPEG-I standards.
  • MPEG-I Immersive Audio: Immersive Audio will complement other parts of MPEG-I (i.e., Part 3, “Immersive Video” and Part 2, “Systems Support”) in order to provide a suite of standards that will support a Virtual Reality (VR) or an Augmented Reality (AR) presentation in which the user can navigate and interact with the environment using 6 degrees of freedom (6 DoF), that being spatial navigation (x, y, z) and user head orientation (yaw, pitch, roll).
  • New Advanced Genomics Features and Technologies: This CfP aims to collect submissions of new technologies that can (i) provide improvements to the current compression, transport, and indexing capabilities of the ISO/IEC 23092 standards suite, particularly applied to data consisting of very long reads generated by 3rd generation sequencing devices, (ii) provide the support for representation and usage of graph genome references, (iii) include coding modes relying on machine learning processes, satisfying data access modalities required by machine learning and providing higher compression, and (iv) support of interfaces with existing standards for the interchange of clinical data.

Detailed information, including instructions on how to respond to the call for proposals, the requirements that must be considered, the test data to be used, and the submission and evaluation procedures for proponents are available at www.mpeg.org.

Call for proposals typically mark the beginning of the formal standardization work whereas verification tests are conducted once a standard has been completed. At the 134th MPEG meeting and despite the difficulties caused by the pandemic situation, MPEG completed verification tests for Versatile Video Coding (VVC) and Low Complexity Enhancement Video Coding (LCEVC).

For LCEVC, verification tests measured the benefits of enhancing four existing codecs of different generations (i.e., AVC, HEVC, EVC, VVC) using tools as defined in LCEVC within two sets of tests:

  • The first set of tests compared LCEVC-enhanced encoding with full-resolution single-layer anchors. The average bit rate savings produced by LCEVC when enhancing AVC were determined to be approximately 46% for UHD and 28% for HD. When enhancing HEVC approximately 31% for UHD and 24% for HD. Test results tend to indicate an overall benefit also when using LCEVC to enhance EVC and VVC.
  • The second set of tests confirmed that LCEVC provided a more efficient means of resolution enhancement of half-resolution anchors than unguided up-sampling. Comparing LCEVC full-resolution encoding with the up-sampled half-resolution anchors, the average bit-rate savings when using LCEVC with AVC, HEVC, EVC and VVC were calculated to be approximately 28%, 34%, 38%, and 32% for UHD and 27%, 26%, 21%, and 21% for HD, respectively.

For VVC, it was already the second round of verification testing including the following aspects:

  • 360-degree video for equirectangular and cubemap formats, where VVC shows on average more than 50% bit rate reduction compared to the previous major generation of MPEG video coding standard known as High Efficiency Video Coding (HEVC), developed in 2013.
  • Low-delay applications such as compression of conversational (teleconferencing) and gaming content, where the compression benefit is about 40% on average,
  • HD video streaming, with an average bit rate reduction of close to 50%.

A previous set of tests for 4K UHD content completed in October 2020 had shown similar gains. These verification tests used formal subjective visual quality assessment testing with “naïve” human viewers. The tests were performed under a strict hygienic regime in two test laboratories to ensure safe conditions for the viewers and test managers.

Research aspects: CfPs offer a unique possibility for researchers to propose research results for adoption into future standards. Verification tests provide objective or/and subjective evaluations of standardized tools which typically conclude the life cycle of a standard. The results of the verification tests are usually publicly available and can be used as a baseline for future improvements of the respective standards including the evaluation thereof.

DASH Update!

Finally, I’d like to provide a brief update on MPEG-DASH! At the 134th MPEG meeting, MPEG Systems recommended the approval of ISO/IEC FDIS 23009-1 5th edition. That is, the MPEG-DASH core specification will be available as 5th edition sometime this year. Additionally, MPEG requests that this specification becomes freely available which also marks an important milestone in the development of the MPEG-DASH standard. Most importantly, the 5th edition of this standard incorporates CMAF support as well as other enhancements defined in the amendment of the previous edition. Additionally, the MPEG-DASH subgroup of MPEG Systems is already working on the first amendment to its 5th edition entitled preroll, nonlinear playback, and other extensions. It is expected that the 5th edition will also impact related specifications within MPEG but also in other Standards Developing Organizations (SDOs) such as DASH-IF, i.e., defining interoperability points (IOPs) for various codecs and others, or CTA WAVE (Web Application Video Ecosystem), i.e., defining device playback capabilities such as the Common Media Client Data (CMCD). Both DASH-IF and CTA WAVE provide means for (conformance) test infrastructure for DASH and CMAF.

An updated overview of DASH standards/features can be found in the Figure below.

MPEG-DASH status as of April 2021.

Research aspects: MPEG-DASH has been ratified almost ten years ago which resulted in a plethora of research articles, mostly related to adaptive bitrate (ABR) algorithms and their impact on the streaming performance including the Quality of Experience (QoE). An overview of bitrate adaptation schemes is provided here including a list of open challenges and issues.

The 135th MPEG meeting will be again an online meeting in July 2021. Click here for more information about MPEG meetings and their developments.

MPEG Column: 133rd MPEG Meeting (virtual/online)

The original blog post can be found at the Bitmovin Techblog and has been modified/updated here to focus on and highlight research aspects.

The 133rd MPEG meeting was once again held as an online meeting, and this time, kicked off with great news, that MPEG is one of the organizations honored as a 72nd Annual Technology & Engineering Emmy® Awards Recipient, specifically the MPEG Systems File Format Subgroup and its ISO Base Media File Format (ISOBMFF) et al.

The official press release can be found here and comprises the following items:

  • 6th Emmy® Award for MPEG Technology: MPEG Systems File Format Subgroup wins Technology & Engineering Emmy® Award
  • Essential Video Coding (EVC) verification test finalized
  • MPEG issues a Call for Evidence on Video Coding for Machines
  • Neural Network Compression for Multimedia Applications – MPEG calls for technologies for incremental coding of neural networks
  • MPEG Systems reaches the first milestone for supporting Versatile Video Coding (VVC) and Essential Video Coding (EVC) in the Common Media Application Format (CMAF)
  • MPEG Systems continuously enhances Dynamic Adaptive Streaming over HTTP (DASH)
  • MPEG Systems reached the first milestone to carry event messages in tracks of the ISO Base Media File Format

In this report, I’d like to focus on ISOBMFF, EVC, CMAF, and DASH.

MPEG Systems File Format Subgroup wins Technology & Engineering Emmy® Award

MPEG is pleased to report that the File Format subgroup of MPEG Systems is being recognized this year by the National Academy for Television Arts and Sciences (NATAS) with a Technology & Engineering Emmy® for their 20 years of work on the ISO Base Media File Format (ISOBMFF). This format was first standardized in 1999 as part of the MPEG-4 Systems specification and is now in its 6th edition as ISO/IEC 14496-12. It has been used and adopted by many other specifications, e.g.:

  • MP4 and 3GP file formats;
  • Carriage of NAL unit structured video in the ISO Base Media File Format which provides support for AVC, HEVC, VVC, EVC, and probably soon LCEVC;
  • MPEG-21 file format;
  • Dynamic Adaptive Streaming over HTTP (DASH) and Common Media Application Format (CMAF);
  • High-Efficiency Image Format (HEIF);
  • Timed text and other visual overlays in ISOBMFF;
  • Common encryption format;
  • Carriage of timed metadata metrics of media;
  • Derived visual tracks;
  • Event message track format;
  • Carriage of uncompressed video;
  • Omnidirectional Media Format (OMAF);
  • Carriage of visual volumetric video-based coding data;
  • Carriage of geometry-based point cloud compression data;
  • … to be continued!

This is MPEG’s fourth Technology & Engineering Emmy® Award (after MPEG-1 and MPEG-2 together with JPEG in 1996, Advanced Video Coding (AVC) in 2008, and MPEG-2 Transport Stream in 2013) and sixth overall Emmy® Award including the Primetime Engineering Emmy® Awards for Advanced Video Coding (AVC) High Profile in 2008 and High-Efficiency Video Coding (HEVC) in 2017, respectively.

Essential Video Coding (EVC) verification test finalized

At the 133rd MPEG meeting, a verification testing assessment of the Essential Video Coding (EVC) standard was completed. The first part of the EVC verification test using high dynamic range (HDR) and wide color gamut (WCG) was completed at the 132nd MPEG meeting. A subjective quality evaluation was conducted comparing the EVC Main profile to the HEVC Main 10 profile and the EVC Baseline profile to AVC High 10 profile, respectively:

  • Analysis of the subjective test results showed that the average bitrate savings for EVC Main profile are approximately 40% compared to HEVC Main 10 profile, using UHD and HD SDR content encoded in both random access and low delay configurations.
  • The average bitrate savings for the EVC Baseline profile compared to the AVC High 10 profile is approximately 40% using UHD SDR content encoded in the random-access configuration and approximately 35% using HD SDR content encoded in the low delay configuration.
  • Verification test results using HDR content had shown average bitrate savings for EVC Main profile of approximately 35% compared to HEVC Main 10 profile.

By providing significantly improved compression efficiency compared to HEVC and earlier video coding standards while encouraging the timely publication of licensing terms, the MPEG-5 EVC standard is expected to meet the market needs of emerging delivery protocols and networks, such as 5G, enabling the delivery of high-quality video services to an ever-growing audience. 

In addition to verification tests, EVC, along with VVC and CMAF were subject to further improvements to their support systems.

Research aspects: as for every new video codec, its compression efficiency and computational complexity are important performance metrics. Additionally, the availability of (efficient) open-source implementations (i.e., x264, x265, soon x266, VVenC, aomenc, et al., etc.) are vital for its adoption in the (academic) research community.

MPEG Systems reaches the first milestone for supporting Versatile Video Coding (VVC) and Essential Video Coding (EVC) in the Common Media Application Format (CMAF)

At the 133rd MPEG meeting, MPEG Systems promoted Amendment 2 of the Common Media Application Format (CMAF) to Committee Draft Amendment (CDAM) status, the first major milestone in the ISO/IEC approval process. This amendment defines:

  • constraints to (i) Versatile Video Coding (VVC) and (ii) Essential Video Coding (EVC) video elementary streams when carried in a CMAF video track;
  • codec parameters to be used for CMAF switching sets with VVC and EVC tracks; and
  • support of the newly introduced MPEG-H 3D Audio profile.

It is expected to reach its final milestone in early 2022. For research aspects related to CMAF, the reader is referred to the next section about DASH.

MPEG Systems continuously enhances Dynamic Adaptive Streaming over HTTP (DASH)

At the 133rd MPEG meeting, MPEG Systems promoted Part 8 of Dynamic Adaptive Streaming over HTTP (DASH) also referred to as “Session-based DASH” to its final stage of standardization (i.e., Final Draft International Standard (FDIS)).

Historically, in DASH, every client uses the same Media Presentation Description (MPD), as it best serves the scalability of the service. However, there have been increasing requests from the industry to enable customized manifests for enabling personalized services. MPEG Systems has standardized a solution to this problem without sacrificing scalability. Session-based DASH adds a mechanism to the MPD to refer to another document, called Session-based Description (SBD), which allows per-session information. The DASH client can use this information (i.e., variables and their values) provided in the SBD to derive the URLs for HTTP GET requests.

An updated overview of DASH standards/features can be found in the Figure below.

MPEG DASH Status as of January 2021.

Research aspects: CMAF is mostly like becoming the main segment format to be used in the context of HTTP adaptive streaming (HAS) and, thus, also DASH (hence also the name common media application format). Supporting a plethora of media coding formats will inevitably result in a multi-codec dilemma to be addressed in the near future as there will be no flag day where everyone will switch to a new coding format. Thus, designing efficient bitrate ladders for multi-codec delivery will an interesting research aspect, which needs to include device/player support (i.e., some devices/player will support only a subset of available codecs), storage capacity/costs within the cloud as well as within the delivery network, and network distribution capacity/costs (i.e., CDN costs).

The 134th MPEG meeting will be again an online meeting in April 2021. Click here for more information about MPEG meetings and their developments.

MPEG Column: 132nd MPEG Meeting (virtual/online)

The original blog post can be found at the Bitmovin Techblog and has been modified/updated here to focus on and highlight research aspects.

The 132nd MPEG meeting was the first meeting with the new structure. That is, ISO/IEC JTC 1/SC 29/WG 11 — the official name of MPEG under the ISO structure — was disbanded after the 131st MPEG meeting and some of the subgroups of WG 11 (MPEG) have been elevated to independent MPEG Working Groups (WGs) and Advisory Groups (AGs) of SC 29 rather than subgroups of the former WG 11. Thus, the MPEG community is now an affiliated group of WGs and AGs that will continue meeting together according to previous MPEG meeting practices and will further advance the standardization activities of the MPEG work program.

The 132nd MPEG meeting was the first meeting with the new structure as follows (incl. Convenors and position within WG 11 structure):

  • AG 2 MPEG Technical Coordination (Convenor: Prof. Jörn Ostermann; for overall MPEG work coordination and prev. known as the MPEG chairs meeting; it’s expected that one can also provide inputs to this AG without being a member of this AG)
  • WG 2 MPEG Technical Requirements (Convenor Dr. Igor Curcio; former Requirements subgroup)
  • WG 3 MPEG Systems (Convenor: Dr. Youngkwon Lim; former Systems subgroup)
  • WG 4 MPEG Video Coding (Convenor: Prof. Lu Yu; former Video subgroup)
  • WG 5 MPEG Joint Video Coding Team(s) with ITU-T SG 16 (Convenor: Prof. Jens-Rainer Ohm; former JVET)
  • WG 6 MPEG Audio Coding (Convenor: Dr. Schuyler Quackenbush; former Audio subgroup)
  • WG 7 MPEG Coding of 3D Graphics (Convenor: Prof. Marius Preda, former 3DG subgroup)
  • WG 8 MPEG Genome Coding (Convenor: Prof. Marco Mattaveli; newly established WG)
  • AG 3 MPEG Liaison and Communication (Convenor: Prof. Kyuheon Kim; (former Communications subgroup)
  • AG 5 MPEG Visual Quality Assessment (Convenor: Prof. Mathias Wien; former Test subgroup).

The 132nd MPEG meeting was held as an online meeting and more than 300 participants continued to work efficiently on standards for the future needs of the industry. As a group, MPEG started to explore new application areas that will benefit from standardized compression technology in the future. A new web site has been created and can be found at http://mpeg.org/.

The official press release can be found here and comprises the following items:

  • Versatile Video Coding (VVC) Ultra-HD Verification Test Completed and Conformance and Reference Software Standards Reach their First Milestone
  • MPEG Completes Geometry-based Point Cloud Compression (G-PCC) Standard
  • MPEG Evaluates Extensions and Improvements to MPEG-G and Announces a Call for Evidence on New Advanced Genomics Features and Technologies
  • MPEG Issues Draft Call for Proposals on the Coded Representation of Haptics
  • MPEG Evaluates Responses to MPEG IPR Smart Contracts CfP
  • MPEG Completes Standard on Harmonization of DASH and CMAF
  • MPEG Completes 2nd Edition of the Omnidirectional Media Format (OMAF)
  • MPEG Completes the Low Complexity Enhancement Video Coding (LCEVC) Standard

In this report, I’d like to focus on VVC, G-PCC, DASH/CMAF, OMAF, and LCEVC.

Versatile Video Coding (VVC) Ultra-HD Verification Test Completed and Conformance & Reference Software Standards Reach their First Milestone

MPEG completed a verification testing assessment of the recently ratified Versatile Video Coding (VVC) standard for ultra-high definition (UHD) content with standard dynamic range, as may be used in newer streaming and broadcast television applications. The verification test was performed using rigorous subjective quality assessment methods and showed that VVC provides a compelling gain over its predecessor — the High-Efficiency Video Coding (HEVC) standard produced in 2013. In particular, the verification test was performed using the VVC reference software implementation (VTM) and the recently released open-source encoder implementation of VVC (VVenC):

  • Using its reference software implementation (VTM), VVC showed bit rate savings of roughly 45% over HEVC for comparable subjective video quality.
  • Using VVenC, additional bit rate savings of more than 10% relative to VTM were observed, which at the same time runs significantly faster than the reference software implementation.

Additionally, the standardization work for both conformance testing and reference software for the VVC standard reached its first major milestone, i.e., progressing to the Committee Draft ballot in the ISO/IEC approval process. The conformance testing standard (ISO/IEC 23090-15) will ensure interoperability among the diverse applications that use the VVC standard, and the reference software standard (ISO/IEC 23090-16) will provide an illustration of the capabilities of VVC and a valuable example showing how the standard can be implemented. The reference software will further facilitate the adoption of the standard by being available for use as the basis of product implementations.

Research aspects: as for every new video codec, its compression efficiency and computational complexity are important performance metrics. While the reference software (VTM) provides a valid reference in terms of compression efficiency it is not optimized for runtime. VVenC seems to provide already a significant improvement and with x266 another open source implementation will be available soon. Together with AOMedia’s AV1 (including its possible successor AV2), we are looking forward to a lively future in the area of video codecs.

MPEG Completes Geometry-based Point Cloud Compression Standard

MPEG promoted its ISO/IEC 23090-9 Geometry-based Point Cloud Compression (G-PCC) standard to the Final Draft International Standard (FDIS) stage. G-PCC addresses lossless and lossy coding of time-varying 3D point clouds with associated attributes such as color and material properties. This technology is particularly suitable for sparse point clouds. ISO/IEC 23090-5 Video-based Point Cloud Compression (V-PCC), which reached the FDIS stage in July 2020, addresses the same problem but for dense point clouds, by projecting the (typically dense) 3D point clouds onto planes, and then processing the resulting sequences of 2D images using video compression techniques. The generalized approach of G-PCC, where the 3D geometry is directly coded to exploit any redundancy in the point cloud itself, is complementary to V-PCC and particularly useful for sparse point clouds representing large environments.

Point clouds are typically represented by extremely large amounts of data, which is a significant barrier to mass-market applications. However, the relative ease of capturing and rendering spatial information compared to other volumetric video representations makes point clouds increasingly popular for displaying immersive volumetric data. The current draft reference software implementation of a lossless, intra-frame G‐PCC encoder provides a compression ratio of up to 10:1 and lossy coding of acceptable quality for a variety of applications with a ratio of up to 35:1.

By providing high immersion at currently available bit rates, the G‐PCC standard will enable various applications such as 3D mapping, indoor navigation, autonomous driving, advanced augmented reality (AR) with environmental mapping, and cultural heritage.

Research aspects: the main research focus related to G-PCC and V-PCC is currently on compression efficiency but one should not dismiss its delivery aspects including its dynamic, adaptive streaming. A recent paper on this topic has been published in the IEEE Communications Magazine and is entitled “From Capturing to Rendering: Volumetric Media Delivery With Six Degrees of Freedom“.

MPEG Finalizes the Harmonization of DASH and CMAF

MPEG successfully completed the harmonization of Dynamic Adaptive Streaming over HTTP (DASH) with Common Media Application Format (CMAF) featuring a DASH profile for the use with CMAF (as part of the 1st Amendment of ISO/IEC 23009-1:2019 4th edition).

CMAF and DASH segments are both based on the ISO Base Media File Format (ISOBMFF), which per se enables smooth integration of both technologies. Most importantly, this DASH profile defines (a) a normative mapping of CMAF structures to DASH structures and (b) how to use Media Presentation Description (MPD) as a manifest format.
Additional tools added to this amendment include

  • DASH events and timed metadata track timing and processing models with in-band event streams,
  • a method for specifying the resynchronization points of segments when the segments have internal structures that allow container-level resynchronization,
  • an MPD patch framework that allows the transmission of partial MPD information as opposed to the complete MPD using the XML patch framework as defined in IETF RFC 5261, and
  • content protection enhancements for efficient signalling.

It is expected that the 5th edition of the MPEG DASH standard (ISO/IEC 23009-1) containing this change will be issued at the 133rd MPEG meeting in January 2021. An overview of DASH standards/features can be found in the Figure below.

Research aspects: one of the features enabled by CMAF is low latency streaming that is actively researched within the multimedia systems community (e.g., here). The main research focus has been related to the ABR logic while its impact on the network is not yet fully understood and requires strong collaboration among stakeholders along the delivery path including ingest, encoding, packaging, (encryption), content delivery network (CDN), and consumption. A holistic view on ABR is needed to enable innovation and the next step towards the future generation of streaming technologies (https://athena.itec.aau.at/).

MPEG Completes 2nd Edition of the Omnidirectional Media Format

MPEG completed the standardization of the 2nd edition of the Omnidirectional MediA Format (OMAF) by promoting ISO/IEC 23009-2 to Final Draft International Standard (FDIS) status including the following features:

  • “Late binding” technologies to deliver and present only that part of the content that adapts to the dynamically changing users’ viewpoint. To enable an efficient implementation of such a feature, this edition of the specification introduces the concept of bitstream rewriting, in which a compliant bitstream is dynamically generated that, by combining the received portions of the bitstream, covers only the users’ viewport on the client.
  • Extension of OMAF beyond 360-degree video. This edition introduces the concept of viewpoints, which can be considered as user-switchable camera positions for viewing content or as temporally contiguous parts of a storyline to provide multiple choices for the storyline a user can follow.
  • Enhances the use of video, image, or timed text overlays on top of omnidirectional visual background video or images related to a sphere or a viewport.

Research aspects: standards usually define formats to enable interoperability but various informative aspects are left open for industry competition and subject to research and development. The same holds for OMAF and its 2nd edition enables researchers and developers to work towards efficient viewport-adaptive implementations focusing on the users’ viewport.

MPEG Completes the Low Complexity Enhancement Video Coding Standard

MPEG is pleased to announce the completion of the new ISO/IEC 23094-2 standard, i.e., Low Complexity Enhancement Video Coding (MPEG-5 Part 2 LCEVC), which has been promoted to Final Draft International Standard (FDIS) at the 132nd MPEG meeting.

  • LCEVC adds an enhancement data stream that can appreciably improve the resolution and visual quality of reconstructed video with an effective compression efficiency of limited complexity by building on top of existing and future video codecs.
  • LCEVC can be used to complement devices originally designed only for decoding the base layer bitstream, by using firmware, operating system, or browser support. It is designed to be compatible with existing video workflows (e.g., CDNs, metadata management, DRM/CA) and network protocols (e.g., HLS, DASH, CMAF) to facilitate the rapid deployment of enhanced video services.
  • LCEVC can be used to deliver higher video quality in limited bandwidth scenarios, especially when the available bit rate is low for high-resolution video delivery and decoding complexity is a challenge. Typical use cases include mobile streaming and social media, and services that benefit from high-density/low-power transcoding.

Research aspects: LCEVC provides a kind of scalable video coding by combining hardware- and software-based decoders that allow for certain flexibility as part of regular software life cycle updates. However, LCEVC has been never compared to Scalable Video Coding (SVC) and Scalable High-Efficiency Video Coding (SHVC) which could be an interesting aspect for future work.

The 133rd MPEG meeting will be again an online meeting in January 2021.

Click here for more information about MPEG meetings and their developments.

Immersive Media Experiences – Why finding Consensus is Important

An introduction to the QUALINET White Paper on Definitions of Immersive Media Experience (IMEx) [1].

Introduction

Immersive media are reshaping the way users experience reality. They are increasingly incorporated across enterprise and consumer sectors to offer experiential solutions to a diverse range of industries. Current technologies that afford an immersive media experience (IMEx) include Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), and 360-degree video. Popular uses can be found in enhancing connectivity applications, supporting knowledge-based tasks, learning & skill development, as well as adding immersive and interactive dimensions to the retail, business, and entertainment industries. Whereas the evolution of immersive media can be traced over the past 50 years, its current popularity boost is primarily owed to significant advances in the last decade brought about by improved connectivity, superior computing, and device capabilities. In specific, advancements witnessed in display technologies, visualizations, interaction & tracking devices, recognition technologies, platform development, new media formats, and increasing user demand for real-time & dynamic content across platforms.

Though still in its infancy, the immersive economy is growing into a dynamic and confident sector. Being an emerging sector, it is hard to find official data, but some estimations project the immersive media global market size to continue its upward growth at around 30% CAGR to reach USD180 Bn by 2022 [2,3]. Country-wise, the USA is expected to secure 1/3rd of the global immersive media market share followed by China, Japan, Germany, and the UK as likely immersive media markets where significant spending is anticipated. Consumer products and devices are poised to be the largest contributing segment. The growth in immersive consumer products is expected to continue as Head-Mounted Displays (HMD) become commonplace and interest in mobile augmented reality increase [4]. However, immersive media are no longer just a pursuit of alternative display technologies but pushing towards holistic ecosystems that seek contributions from hardware manufacturers, application & platform developers, content producers, and users. These ecosystems are making way for sophisticated content creation available on platforms that allow user participation, interaction, and skill integration through advanced tools.

Immersive media experience (IMEx), today, is not only how users view media but in fact a transformative way to consume media altogether. They draw considerable interdisciplinary interest from multiple disciplines. As stakeholders increase, the need for clarity and coherence on definitions and concepts become all the more important. In this article, we provide an overview and a brief survey of some of the key definitions that are central to IMEx including its Quality of Experience (QoE), application areas, influencing factors, and assessment methods. Our aim is to enable some clarity and initiate consensus, on topics related to IMEx that can be useful for researchers and practitioners working both inside academia and the industry.

Why understand IMEx?

IMEx combines reality with technology enabling emplaced multimedia experiences of standard media (film, photographic, or animated) as well as synthetic and interactive environments for users. They utilize visual, auditory, and haptic feedback to stimulate physical senses such that users psychologically feel immersed within these multidimensional media environments. This sense of “being there” is also referred to as presence.

As mentioned earlier, the enthusiasm for IMEx is mainly driven by the gaming, entertainment, retail, healthcare, digital marketing, and skill training industries. So far, research has tilted favourably towards innovation, with a particular interest in image capture, recognition, mapping, and display technologies over the past few years. However, the prevalence of IMEx has also ushered in a plethora of definitions, frameworks, and models to understand the psychological and phenomenological concepts associated with these media forms. Central, of course, are the closely related concepts of immersion and presence, which are interpreted varyingly across fields; for example, when one moves from literature to narratology to computer sciences. However, with immersive media, these three separate fields come together inside interactive digital narrative applications where immersive narratives are used to solve real-world problems. This is when noticeable interdisciplinary differences regarding definitions, scope, and constituents require urgent redressal to achieve a coherent understanding of the used concepts. Such consensus is vital for giving directionality to the future of immersive media that can be shared by all.

A White Paper on IMEx

A recent White Paper [1] by QUALINET, the European Network on Quality of Experience in Multimedia Systems and Services [5], is a contribution to the discussions related to Immersive Media Experience (IMEx). It attempts to build consensus around ideas and concepts that are related to IMEx but originate from multidisciplinary groups with a joint interest in multimedia experiences.

The QUALINET community aims at extending the notion of network-centric Quality of Service (QoS) in multimedia systems, by relying on the concept of Quality of Experience (QoE). The main scientific objective is the development of methodologies for subjective and objective quality metrics considering current and new trends in multimedia communication systems as witnessed by the appearance of new types of content and interactions.

The white paper was created based on an activity launched at the 13th QUALINET meeting on June 4, 2019, in Berlin as part of Task Force 7, Immersive Media Experiences (IMEx). The paper received contributions from 44 authors under 10 section leads, which were consolidated into a first draft and released among all section leads and editors for internal review. After incorporating the feedback from all section leads, the editors initially released the White Paper within the QUALINET community for review. Following feedback from QUALINET at large, the editors distributed the White Paper widely for an open, public community review (e.g., research communities/committees in ACM and IEEE, standards development organizations, various open email reflectors related to this topic). The feedback received from this public consultation process resulted in the final version which has been approved during the 14th QUALINET meeting on May 25, 2020.

Understanding the White Paper

The White Paper surveys definitions and concepts that contribute to IMEx. It describes the Quality of Experience (QoE) for immersive media by establishing a relationship between the concepts of QoE and IMEx. This article provides an outline of these concepts by looking at:

  • Survey of definitions of immersion and presence discusses various frameworks and conceptual models that are most relevant to these phenomena in terms of multimedia experiences.
  • Definition of immersive media experience describes experiential determinants for IMEx characterized through its various technological contexts.
  • Quality of experience for immersive media applies existing QoE concepts to understand the user-centric subjective feelings of “a sense of being there”, “a sense of agency”, and “cybersickness”.
  • The application area for immersive media experience presents an overview of immersive technologies in use within gaming, omnidirectional content, interactive storytelling, health, entertainment, and communications.
  • Influencing factors on immersive media experience look at the three existing influence factors on QoE with a pronounced emphasis on the human influence factor as of very high relevance to IMEx.
  • Assessment of immersive media experience underscores the importance of proper examination of multimedia systems, including IMEx, by highlighting three methods currently in use, i.e., subjective, behavioural, and psychophysiological.
  • Standardization activities discuss the three clusters of activities currently underway to achieve interoperability for IMEx: (i) data representation & formats; (ii) guidelines, systems standards, & APIs; and (iii) Quality of Experience (QoE).

Conclusions

Immersive media have significantly changed the use and experience of new digital media. These innovative technologies transcend traditional formats and present new ways to interact with digital information inside synthetic or enhanced realities, which include VR, AR, MR, and haptic communications. Earlier the need for a multidisciplinary consensus was discussed vis-à-vis definitions of IMEx. The QUALINET white paper provides such “a toolbox of definitions” for IMEx. It stands out for bringing together insights from multimedia groups spread across academia and industry, specifically the Video Quality Experts Group (VQEG) and the Immersive Media Group (IMG). This makes it a valuable asset for those working in the field of IMEx going forward.

References

[1] Perkis, A., Timmerer, C., et al., “QUALINET White Paper on Definitions of Immersive Media Experience (IMEx)”, European Network on Quality of Experience in Multimedia Systems and Services, 14th QUALINET meeting (online), May 25, 2020. Online: https://arxiv.org/abs/2007.07032
[2] Mateos-Garcia, J., Stathoulopoulos, K., & Thomas, N. (2018). The immersive economy in the UK (Rep. No. 18.1137.020). Innovate UK.
[3] Infocomm Media 2025 Supplementary Information (pp. 31-43, Rep.). (2015). Singapore: Ministry of Communications and Information.
[4] Hadwick, A. (2020). XR Industry Insight Report 2019-2020 (Rep.). San Francisco: VRX Conference & Expo.
[5] http://www.qualinet.eu/

MPEG Column: 131st MPEG Meeting (virtual/online)

The original blog post can be found at the Bitmovin Techblog and has been modified/updated here to focus on and highlight research aspects.

The 131st MPEG meeting concluded on July 3, 2020, online, again but with a press release comprising an impressive list of news items which is led by “MPEG Announces VVC – the Versatile Video Coding Standard”. Just in the middle of the SC 29 (i.e., MPEG’s parent body within ISO) restructuring process, MPEG successfully ratified — jointly with ITU-T’s VCEG within JVET — its next-generation video codec among other interesting results from the 131st MPEG meeting:

Standards progressing to final approval ballot (FDIS)

  • MPEG Announces VVC – the Versatile Video Coding Standard
  • Point Cloud Compression – MPEG promotes a Video-based Point Cloud Compression Technology to the FDIS stage
  • MPEG-H 3D Audio – MPEG promotes Baseline Profile for 3D Audio to the final stage

Call for Proposals

  • Call for Proposals on Technologies for MPEG-21 Contracts to Smart Contracts Conversion
  • MPEG issues a Call for Proposals on extension and improvements to ISO/IEC 23092 standard series

Standards progressing to the first milestone of the ISO standard development process

  • Widening support for storage and delivery of MPEG-5 EVC
  • Multi-Image Application Format adds support of HDR
  • Carriage of Geometry-based Point Cloud Data progresses to Committee Draft
  • MPEG Immersive Video (MIV) progresses to Committee Draft
  • Neural Network Compression for Multimedia Applications – MPEG progresses to Committee Draft
  • MPEG issues Committee Draft of Conformance and Reference Software for Essential Video Coding (EVC)

The corresponding press release of the 131st MPEG meeting can be found here: https://mpeg-standards.com/meetings/mpeg-131/. This report focused on video coding featuring VVC as well as PCC and systems aspects (i.e., file format, DASH).

MPEG Announces VVC – the Versatile Video Coding Standard

MPEG is pleased to announce the completion of the new Versatile Video Coding (VVC) standard at its 131st meeting. The document has been progressed to its final approval ballot as ISO/IEC 23090-3 and will also be known as H.266 in the ITU-T.

VVC Architecture (from IEEE ICME 2020 tutorial of Mathias Wien and Benjamin Bross)

VVC is the latest in a series of very successful standards for video coding that have been jointly developed with ITU-T, and it is the direct successor to the well-known and widely used High Efficiency Video Coding (HEVC) and Advanced Video Coding (AVC) standards (see architecture in the figure above). VVC provides a major benefit in compression over HEVC. Plans are underway to conduct a verification test with formal subjective testing to confirm that VVC achieves an estimated 50% bit rate reduction versus HEVC for equal subjective video quality. Test results have already demonstrated that VVC typically provides about a 40%-bit rate reduction for 4K/UHD video sequences in tests using objective metrics (i.e., PSNR, VMAF, MS-SSIM). Application areas especially targeted for the use of VVC include:

  • ultra-high definition 4K and 8K video,
  • video with a high dynamic range and wide colour gamut, and
  • video for immersive media applications such as 360° omnidirectional video.

Furthermore, VVC is designed for a wide variety of types of video such as camera capturedcomputer-generated, and mixed content for screen sharing, adaptive streaming, game streaming, video with scrolling text, etc. Conventional standard-definition and high-definition video content are also supported with similar gains in compression. In addition to improving coding efficiency, VVC also provides highly flexible syntax supporting such use cases as (i) subpicture bitstream extraction, (ii) bitstream merging, (iii) temporal sub-layering, and (iv) layered coding scalability.

The current performance of VVC compared to HEVC-HM is shown in the figure below which confirms the statement above but also highlights the increased complexity. Please note that VTM9 is not optimized for speed but functionality (i.e., compression efficiency).

Performance of VVC, VTM9 vs. HM (taken from https://bit.ly/mpeg131).

MPEG also announces completion of ISO/IEC 23002-7 “Versatile supplemental enhancement information for coded video bitstreams” (VSEI), developed jointly with ITU-T as Rec. ITU-T H.274. The new VSEI standard specifies the syntax and semantics of video usability information (VUI) parameters and supplemental enhancement information (SEI) messages for use with coded video bitstreams. VSEI is especially intended for use with VVC, although it is drafted to be generic and flexible so that it may also be used with other types of coded video bitstreams. Once specified in VSEI, different video coding standards and systems-environment specifications can re-use the same SEI messages without the need for defining special-purpose data customized to the specific usage context.

At the same time, the Media Coding Industry Forum (MC-IF) announces a VVC patent pool fostering with an initial meeting on September 1, 2020. The aim of this meeting is to identify tasks and to propose a schedule for VVC pool fostering with the goal to select a pool facilitator/administrator by the end of 2020. MC-IF is not facilitating or administering a patent pool.

At the time of writing this blog post, it is probably too early to make an assessment of whether VVC will share the fate of HEVC or AVC (w.r.t. patent pooling). AVC is still the most widely used video codec but with AVC, HEVC, EVC, VVC, LCEVC, AV1, (AV2), and probably also AVS3 — did I miss anything? — the competition and pressure are certainly increasing.

Research aspects: from a research perspective, reduction of time-complexity (for a variety of use cases) while maintaining quality and bitrate at acceptable levels is probably the most relevant aspect. Improvements in individual building blocks of VVC by using artificial neural networks (ANNs) are another area of interest but also end-to-end aspects of video coding using ANNs will probably pave the roads towards the/a next generation of video codec(s). Utilizing VVC and its features for HTTP adaptive streaming (HAS) is probably most interesting for me but maybe also for others…

MPEG promotes a Video-based Point Cloud Compression Technology to the FDIS stage

At its 131st meeting, MPEG promoted its Video-based Point Cloud Compression (V-PCC) standard to the Final Draft International Standard (FDIS) stage. V-PCC addresses lossless and lossy coding of 3D point clouds with associated attributes such as colors and reflectance. Point clouds are typically represented by extremely large amounts of data, which is a significant barrier for mass-market applications. However, the relative ease to capture and render spatial information as point clouds compared to other volumetric video representations makes point clouds increasingly popular to present immersive volumetric data. With the current V-PCC encoder implementation providing compression in the range of 100:1 to 300:1, a dynamic point cloud of one million points could be encoded at 8 Mbit/s with good perceptual quality. Real-time decoding and rendering of V-PCC bitstreams have also been demonstrated on current mobile hardware. The V-PCC standard leverages video compression technologies and the video ecosystem in general (hardware acceleration, transmission services, and infrastructure) while enabling new kinds of applications. The V-PCC standard contains several profiles that leverage existing AVC and HEVC implementations, which may make them suitable to run on existing and emerging platforms. The standard is also extensible to upcoming video specifications such as Versatile Video Coding (VVC) and Essential Video Coding (EVC).

The V-PCC standard is based on Visual Volumetric Video-based Coding (V3C), which is expected to be re-used by other MPEG-I volumetric codecs under development. MPEG is also developing a standard for the carriage of V-PCC and V3C data (ISO/IEC 23090-10) which has been promoted to DIS status at the 130th MPEG meeting.

By providing high-level immersiveness at currently available bandwidths, the V-PCC standard is expected to enable several types of applications and services such as six Degrees of Freedom (6 DoF) immersive media, virtual reality (VR) / augmented reality (AR), immersive real-time communication and cultural heritage.

Research aspects: as V-PCC is video-based, we can probably state similar research aspects as for video codecs such as improving efficiency both for encoding and rendering as well as reduction of time complexity. During the development of V-PCC mainly HEVC (and AVC) has/have been used but it is definitely interesting to use also VVC for PCC. Finally, the dynamic adaptive streaming of V-PCC data is still in its infancy despite some articles published here and there.

MPEG Systems related News

Finally, I’d like to share news related to MPEG systems and the carriage of video data as depicted in the figure below. In particular, the carriage of VVC (and also EVC) has been now enabled in MPEG-2 Systems (specifically within the transport stream) and in the various file formats (specifically within the NAL file format). The latter is used also in CMAF and DASH which makes VVC (and also EVC) ready for HTTP adaptive streaming (HAS).

Carriage of Video in MPEG Systems Standards (taken from https://bit.ly/mpeg131).

What about DASH and CMAF?

CMAF maintains a so-called “technologies under consideration” document which contains — among other things — a proposed VVC CMAF profile. Additionally, there are two exploration activities related to CMAF, i.e., (i) multi-stream support and (ii) storage, archiving, and content management for CMAF files.

DASH works on potential improvement for the first amendment to ISO/IEC 23009-1 4th edition related to CMAF support, events processing model, and other extensions. Additionally, there’s a working draft for a second amendment to ISO/IEC 23009-1 4th edition enabling bandwidth change signalling track and other enhancements. Furthermore, ISO/IEC 23009-8 (Session-based DASH operations) has been advanced to Draft International Standard (see also my last report).

An overview of the current status of MPEG-DASH can be found in the figure below.

The next meeting will be again an online meeting in October 2020.

Finally, MPEG organized a Webinar presenting results from the 131st MPEG meeting. The slides and video recordings are available here: https://bit.ly/mpeg131.

Click here for more information about MPEG meetings and their developments.

MPEG Column: 130th MPEG Meeting (virtual/online)

The original blog post can be found at the Bitmovin Techblog and has been modified/updated here to focus on and highlight research aspects.

The 130th MPEG meeting concluded on April 24, 2020, in Alpbach, Austria … well, not exactly, unfortunately. The 130th MPEG meeting concluded on April 24, 2020, but not in Alpbach, Austria.

I attended the 130th MPEG meeting remotely.

Because of the Covid-19 pandemic, the 130th MPEG meeting has been converted from a physical meeting to a fully online meeting, the first in MPEG’s 30+ years of history. Approximately 600 experts attending from 19 time zones worked in tens of Zoom meeting sessions supported by an online calendar and by collaborative tools that involved MPEG experts in both online and offline sessions. For example, input contributions had to be registered and uploaded ahead of the meeting to allow for efficient scheduling of two-hour meeting slots, which have been distributed from early morning to late night in order to accommodate experts working in different time zones as mentioned earlier. These input contributions have been then mapped to GitLab issues for offline discussions and the actual meeting slots have been primarily used for organizing the meeting, resolving conflicts, and making decisions including approving output documents. Although the productivity of the online meeting could not reach the level of regular face-to-face meetings, the results posted in the press release show that MPEG experts managed the challenge quite well, specifically

  • MPEG ratifies MPEG-5 Essential Video Coding (EVC) standard;
  • MPEG issues the Final Draft International Standards for parts 1, 2, 4, and 5 of MPEG-G 2nd edition;
  • MPEG expands the coverage of ISO Base Media File Format (ISOBMFF) family of standards;
  • A new standard for large scale client-specific streaming with MPEG-DASH;

Other Important Activities at the 130th MPEG meeting(i) the carriage of visual volumetric video-based coding data, (ii) Network-Based Media Processing (NBMP) function templates, (iii) the conversion from MPEG-21 contracts to smart contracts, (iv) deep neural network-based video coding, (v) Low Complexity Enhancement Video Coding (LCEVC) reaching DIS stage, and (vi) a new level of the MPEG-4 Audio ALS Simple Profile for high-resolution audio among others

The corresponding press release of the 130th MPEG meeting can be found here: https://mpeg.chiariglione.org/meetings/130. This report focused on video coding (EVC) and systems aspects (file format, DASH).

MPEG ratifies MPEG-5 Essential Video Coding Standard

At its 130th meeting, MPEG announced the completion of the new ISO/IEC 23094-1 standard which is referred to as MPEG-5 Essential Video Coding (EVC) and has been promoted to Final Draft International Standard (FDIS) status. There is a constant demand for more efficient video coding technologies (e.g., due to the increased usage of video on the internet), but coding efficiency is not the only factor determining the industry’s choice of video coding technology for products and services. The EVC standard offers improved compression efficiency compared to existing video coding standards and is based on the statements of all contributors to the standard who have committed announcing their license terms for the MPEG-5 EVC standard no later than two years after the FDIS publication date.

The MPEG-5 EVC defines two important profiles, including “Baseline profile” and “Main profile”. The “Baseline Profile” contains only technologies that are older than 20 years or otherwise freely available for use in the standard. In addition, the “Main Profile” adds a small number of additional tools, each of which can be either cleanly disabled or switched to the corresponding baseline tool on an individual basis.

It will be interesting to see how EVC profiles (baseline and main) will find its path into products and services given the existing number of codecs already in use (e.g., AVC, HEVC, VP9, AV1) and those still under development but being close to ratification (e.g., VVC, LCEVC). That is, in total, we may end up with about seven video coding formats that probably need to be considered for future video products and services. In other words, the multi-codec scenario I have envisioned some time ago is becoming reality raising some interesting challenges to be addressed in the future.

Research aspects: as for all video coding standards, the most important research aspect is certainly coding efficiency. For EVC it might be also interesting to research its usability of the built-in tool switching mechanism within a practical setup. Furthermore, the multi-codec issue, the ratification of EVC adds another facet to the already existing video coding standards in use or/and under development.

MPEG expands the Coverage of ISO Base Media File Format (ISOBMFF) Family of Standards

At the 130th WG11 (MPEG) meeting, the ISOBMFF family of standards has been significantly amended with new tools and functionalities. The standards in question are as follows:

  • ISO/IEC 14496-12: ISO Base Media File Format;
  • ISO/IEC 14496-15: Carriage of network abstraction layer (NAL) unit structured video in the ISO base media file format;
  • ISO/IEC 23008-12: Image File Format; and
  • ISO /IEC 23001-16: Derived visual tracks in the ISO base media file format.

In particular, three new amendments to the ISOBMFF family have reached their final milestone, i.e., Final Draft Amendment (FDAM):

  1. Amendment 4 to ISO/IEC 14496-12 (ISO Base Media File Format) allows the use of a more compact version of metadata for movie fragments;
  2. Amendment 1 to ISO/IEC 14496-15 (Carriage of network abstraction layer (NAL) unit structured video in the ISO base media file format) adds support of HEVC slice segment data track and additional extractor types for HEVC such as track reference and track groups; and
  3. Amendment 2 to ISO/IEC 23008-12 (Image File Format) adds support for more advanced features related to the storage of short image sequences such as burst and bracketing shots.

At the same time, new amendments have reached their first milestone, i.e., Committee Draft Amendment (CDAM):

  1. Amendment 2 to ISO/IEC 14496-15 (Carriage of network abstraction layer (NAL) unit structured video in the ISO base media file format) extends its scope to newly developed video coding standards such as Essential Video Coding (EVC) and Versatile Video Coding (VVC); and
  2. the first edition of ISO/IEC 23001-16 (Derived visual tracks in the ISO base media file format) allows a new type of visual track whose content can be dynamically generated at the time of presentation by applying some operations to the content in other tracks, such as crossfading over two tracks.

Both are expected to reach their final milestone in mid-2021.

Finally, the final text for the ISO/IEC 14496-12 6th edition Final Draft International Standard (FDIS) is now ready for the ballot after converting MP4RA to the Maintenance Agency. WG11 (MPEG) notes that Apple Inc. has been appointed as the Maintenance Agency and MPEG appreciates its valuable efforts for the many years while already acting as the official registration authority for the ISOBMFF family of standards, i.e., MP4RA (https://mp4ra.org/). The 6th edition of ISO/IEC 14496-12 is expected to be published by ISO by the end of this year.

Research aspects: the ISOBMFF family of standards basically offers certain tools and functionalities to satisfy the given use case requirements. The task of the multimedia systems research community could be to scientifically validate these tools and functionalities with respect to the use cases and maybe even beyond, e.g., try to adopt these tools and functionalities for novel applications and services.

A New Standard for Large Scale Client-specific Streaming with DASH

Historically, in ISO/IEC 23009 (Dynamic Adaptive Streaming over HTTP; DASH), every client has used the same Media Presentation Description (MPD) as it best serves the scalability of the service (e.g., for efficient cache efficiency in content delivery networks). However, there have been increasing requests from the industry to enable customized manifests for more personalized services. Consequently, MPEG has studied a solution to this problem without sacrificing scalability, and it has reached the first milestone of its standardization at the 130th MPEG meeting.

ISO/IEC 23009-8 adds a mechanism to the Media Presentation Description (MPD) to refer to another document, called Session-based Description (SBD), which allows per-session information. The DASH client can use this information (i.e., variables and their values) provided in the SBD to derive the URLs for HTTP GET requests. This standard is expected to reach its final milestone in mid-2021.

Research aspects: SBD’s goal is to enable personalization while maintaining scalability which calls for a tradeoff, i.e., which kind of information to put into the MPD and what should be conveyed within the SBD. This tradeoff per se could be considered already a research question that will be hopefully addressed in the near future.

An overview of the current status of MPEG-DASH can be found in the figure below.

The next MPEG meeting will be from June 29th to July 3rd and will be again an online meeting. I am looking forward to a productive AhG period and an online meeting later this year. I am sure that MPEG will further improve its online meeting capabilities and can certainly become a role model for other groups within ISO/IEC and probably also beyond.