Monday, September 4, 2017

MPEG news: a report from the 119th meeting, Turin, Italy

The original blog post can be found at the Bitmovin Techblog and has been updated here to focus on and highlight research aspects. Additionally, this version of the blog post will be also posted at ACM SIGMM Records.


The MPEG press release comprises the following topics:
  • Evidence of New Developments in Video Compression Coding
  • Call for Evidence on Transcoding for Network Distributed Video Coding
  • 2nd Edition of Storage of Sample Variants reaches Committee Draft
  • New Technical Report on Signalling, Backward Compatibility and Display Adaptation for HDR/WCG Video Coding
  • Draft Requirements for Hybrid Natural/Synthetic Scene Data Container

Evidence of New Developments in Video Compression Coding

At the 119th MPEG meeting, responses to the previously issued call for evidence have been evaluated and they have all successfully demonstrated evidence. The call requested responses for use cases of video coding technology in three categories:
  • standard dynamic range (SDR) — two responses;
  • high dynamic range (HDR) — two responses; and
  • 360° omnidirectional video — four responses.
The evaluation of the responses included subjective testing and an assessment of the performance of the “Joint Exploration Model” (JEM).

The results indicate significant gains over HEVC for a considerable number of test cases with comparable subjective quality at 40-50% less bit rate compared to HEVC for the SDR and HDR test cases with some positive outliers (i.e., higher bit rate savings). Thus, the MPEG-VCEG Joint Video Exploration Team (JVET) concluded that evidence exists of compression technology that may significantly outperform HEVC after further development to establish a new standard. As a next step, the plan is to issue a call for proposals at 120th MPEG meeting (October 2017) and responses expected to be evaluated at the 122th MPEG meeting (April 2018).

We already witness an increase of research articles addressing video coding technologies with capabilities beyond HEVC which will further increase in the future. The main driving force is over the top (OTT) delivery which calls for more efficient bandwidth utilization. However, competition is also increasing with the emergence of AV1 of AOMedia and we may observe also an increasing number of articles in that direction including evaluations thereof. An interesting aspect is also that the number of use cases is also increasing (e.g., see different categories above), which adds further challenges to the "complex video problem".

Call for Evidence on Transcoding for Network Distributed Video Coding

The call for evidence on transcoding for network distributed video coding targets interested parties possessing technology providing transcoding of video at lower computational complexity than transcoding done using a full re-encode. The primary application is adaptive bitrate streaming where a highest bitrate stream is transcoded into lower bitrate streams. It is expected that responses may use “side streams” (or side information, some may call it metadata) accompanying the highest bitrate stream to assist in the transcoding process. MPEG expects submissions for the 120th MPEG meeting where compression efficiency and computational complexity will be assessed.

Transcoding has been discussed already for a long time and I can certainly recommend this article from 2005 published in the Proceedings of the IEEE. The question is, what is different now, 12 years later, and what metadata (or side streams/information) is required for interoperability among different vendors (if any)?

A Brief Overview of Remaining Topics...

  • The 2nd edition of storage of sample variants reaches Committee Draft and expands its usage to MPEG-2 transport stream whereas the first edition primarily focused on ISO base media file format.
  • The new technical report for high dynamic range (HDR) and wide colour gamut (WCG) video coding comprises a survey of various signaling mechanisms including backward compatibility and display adaptation.
  • MPEG issues draft requirements for a scene representation media container enabling the interchange of content for authoring and rendering rich immersive experiences which is currently referred to as hybrid natural/synthetic scene (HNSS) data container.

Other MPEG (Systems) Activities at the 119th Meeting

DASH is in fully maintenance mode as only minor enhancements/corrections have been discussed including contributions to conformance and reference software. The omnidirectional media format (OMAF) is certainly the hottest topic within MPEG systems which is actually between two stages (i.e., between DIS and FDIS) and, thus, a study of DIS has been approved and national bodies are kindly requested to take this into account when casting their votes (incl. comments). The study of DIS comprises format definitions with respect to coding and storage of omnidirectional media including audio and video (aka 360°). The common media application format (CMAF) has been ratified at the last meeting and awaits publications by ISO. In the meantime CMAF is focusing on conformance and reference software as well as amendments regarding various media profiles. Finally, requirements for a multi-image application format (MiAF) are available since the last meeting and at the 119th MPEG meeting a work draft has been approved. MiAF will be based on HEIF and the goal is to define additional constraints to simplify its file format options.

We have successfully demonstrated live 360 adaptive streaming as described here but we expect various improvements from standards available and under development of MPEG. Research aspects in these areas are certainly interesting in the area of performance gains and evaluations with respect to bandwidth efficiency in open networks as well as how these standardization efforts could be used to enable new use cases. 

Publicly available documents from the 119th MPEG meeting can be found here (scroll down to the end of the page). The next MPEG meeting will be held in Macau, China, October 23-27, 2017. Feel free to contact me for any questions or comments.
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