Looking inside an MPEG meeting

Introduction

In There is more to say about MPEG standards I presented the entire spectrum of MPEG standards. No one should deny that it is an impressive set of disparate technologies integrated to cover  fields connected by the common thread of Data Compression: Coding of Video, Audio, 3D Graphics, Fonts, Digital Items, Sensors and Actuators Data, Genome, and Neural Networks; Media Description and Composition; Systems support; Intellectual Property Management and Protection (IPMP); Transport; Application Formats; API; and Media Systems.

How on earth can all these technologies be specified and integrated in MPEG standards to respond to industry needs?

This article will try and answer this question. It will do so by starting, as many novels do, from the end (of an MPEG meeting).

Let’s start from the end (of an MPEG meeting)

When an MPEG meeting closes, the plenary approves the results of the week, marking the end of formal collaborative work within the meeting. Back in 1990 MPEG developed a mechanism – called “ad hoc group” (AhG) – that would allow to continue a form of collaboration. This mechanism allows MPEG experts to continue working together, albeit with limitations:

  1. In the scope, i.e. an AhG may only work on the areas identified by the mandates (in Latin ad hoc means “for a specific purpose”). Of course experts are free to work individually on anything and in any way that please them;
  2. In the purpose, i.e. an AhG may only prepare recommendations – in the scope of its mandates – to be submitted to MPEG. This is done at the beginning of the following meeting, after which the AhG is disbanded;
  3. In the method of work, i.e. an AhG operates under the leadership of one or more Chairs. Clearly, though, the success of an AhG depends very much on the attitude and activity of its members.

On average some 25 AhGs are established at each meeting. There is not one-to-one correspondence between MPEG activities and AhGs. Actually AhGs are great opportunities to explore new and possibly cross-subgroup ideas.

Examples of AhG titles are

  1. Scene Description for MPEG-I
  2. System technologies for Point Cloud Coding (PCC)
  3. Network Based Media Processing (NBMP)
  4. Compression of Neural Networks (NNR).

What happens between MPEG meetings

An AhG uses different means to carry out collaborative work:  by using reflectors, by teleconferencing and by holding physical meetings. The last can only be held if they were scheduled in the AhG establishment form. Unscheduled physical meetings may only be held if there is unanimous agreement of those who subscribed to the AhG.

Most AhGs hold scheduled meetings on the weekend that precedes the next MPEG meeting. These are very useful to coordinate the results of the work done and to prepare the report that all AhGs must make to the MPEG plenary on the following Monday.

AhG meetings, including those in the weekend preceding the MPEG meeting, are not formally part of an MPEG meeting.

An MPEG meeting at a glance

Chairs meeting

MPEG chairs meet three times during an MPEG week:

  1. On Sunday evening to review the progress of AhG work, coordinate activities impacting more than one Subgroup and plan activities to be carried out during the week including the need for joint meetings;
  2. On Tuesday evening to assess the result of the first two days of work, review the work plan and time lines based on the expected outcomes and identify the need of new joint meetings;
  3. On Thursday evening to wrap up the expected results and review the preliminary results of the week.

Plenary meetings

During an MPEG week MPEG holds 3 plenaries

  1. On Monday morning: to make everybody aware of the results of work carried out since the last meeting and to plan work of the week. AHG reports are a main part of it as they are presented and, when necessary, discussed;
  2. On Wednesday morning to make everybody aware of the work done in all subgroups in the first two days and to plan work for the next two days;
  3. On Friday afternoon to approve the results of the work of Subgroups, including liaison letters, to establish new AhGs etc.

Subgroup, Breakout Group and Joint meetings

Subgroups start their meetings on Monday afternoon. They review their own activities and kick off work in their areas. Each subgroup assigns activities to breakout groups (BoG) who meet with their own schedules to achieve the goals assigned. Each Subgroup may hold other brief meetings to keep everybody in the Subgroup in sync with the general progress of the work.

For instance, the activities of the Systems Subgroups are currently: File format, DASH, OMAF, OMAF and DASH, OMAF and MIAF, MPEG Media Transport, Network Based Media Processing and PCC Systems.

The MPEG structure is designed to facilitate interactions between different Subgroups and BoGs from different Subgroups to discuss matters that affect different Subgroups and BoGs, because they are at the interface of MPEG subsystems, For example, the table below lists the joint meetings that the Systems Subgroup held with other Subgroups at the January 2019 meeting.

Table 1 – Joint meeting of Systems Subgroup with other Subgroups

Systems meeting with Topics
Reqs, Video, VCEG SEI messages in VVC
Audio, 3DG Scene Description
3DG Systems for Point Cloud Compression
3DG API for multiple decoders
Audio Uncompressed Audio
Reqs, JVET, VCEG Immersive Decoding Interface

NB: VCEG is the Video Coding Experts Group of ITU-T Study Group 16. It is not an MPEG Subgroup.

On Friday morning all Subgroups approve their own results. These are automatically integrated in the general document to be approved by the MPEG Plenary on Friday afternoon.

Advisors meeting

On Monday evening, an informal group of experts from different countries examines issues of general (non-technical) interest. In particular it calls for meeting hosts, reviews proposals of meeting hosts, makes recommendations of meeting hosts to the plenary etc.

A bird’s eye view of an MPEG meeting

Figure 1 depicts the workflow described in the paragraphs above, starting from the end of the N-1 th meeting to the end of the N-th meeting.

Figure 1 – A snapshot of MPEG works from the end of a meeting to the end of the next meeting

What is “done” at an MPEG meeting?

There are around 500 of the best worldwide experts attending an MPEG meeting. It is an incredible amount of brain power that is mobilised at an MPEG meeting. In the following I will try and explain how this brain power is directed.

An example – the video area

Let’s take as example the work done in the Video Coding area at the March 2019 meeting.

The table below has 3 columns:

  1. The standards on which work is done (Video has worked on MPEG-H, MPEG-I, MPEG-CICP, MPEG-5 and Explorations)
  2. The names of the activities and
  3. The types of documents resulting from the activities (see the following legend for an explanation of the acronyms).

Table 2 – Documents produced in the video coding area

Std Activity Document type
H High Efficiency (HEVC) TM, CE, CTC
I Versatile Video Coding (VVC) WD, TM, CE, CTC
3 Degrees of Freedom + (3DoF+) coding CfP, WD, TM, CE, CTC
CICP Usage of video signal type code points (Ed. 1) TR
Usage of video signal type code points (Ed. 2) WD
5 Essential Video Coding WD, TM, CE, CTC
Low Complexity Enhancement Video Coding CfP, WD, TM, CE, CTC
Expl 6 Degrees of Freedom (6DoF) coding EE, Tools
Coding of dense representation of light fields EE, CTC

Legend

TM: Test Model, software implementing the standard (encoder & decoder)

WD: Working Draft

CE: Core Experiment, i.e. definition of and experiment that should improve performance

CTC: Common Test Conditions, to be used by all CE participants

CfP: Call for Proposals (this time no new CfP produced, but reports and analyses of submissions in response to CfPs)

TR: Technical Report (ISO document)

EE: Exploration Experiment, an experiment to explore an issue because it si not mature enough to be a CE

Tools: other supporting material, e.g. software developed for common use in CEs/EEs

What is produced by an MPEG meeting

Figure 2 gives the number of activities for each type of activity defined in the legend (and others that were not part of the work in the video area). For instance, out of a total of 97 activities:

  1. 29 relate to processing of standards through the canonical stages of Committee Draft (CD), Draft International Standard (DIS) and Draft International Standard (FDIS) and the equivalent for Amendments, Technical Reports and Corrigenda. In other words, at every meeting MPEG is working on ~10 “deliverables” (i.e. standards, amendments, technical reports or corrigenda) in the approval stages;
  2. 22 relate to working drafts, i.e. “new” activities that have not entered the approval stages;
  3. 8 relate to Technologies under Consideration, i.e. new technologies that are being considered to enhance existing standards;
  4. 8 relate to requirements, typically for new standards;
  5. 6 relate to Core Experiments;
  6. Etc.

 

Figure 2 – Activities at an MPEG meeting

Figure 2 does not provide a quantitative measure of “how many” documents were produced for each activity or “how big” they were.  As an example, Point Cloud Compression has 20 Core Experiments and 8 Exploration Experiments under way, while MPEG-5 EVC has only one large CE.

An average value of activity at the March 2019 meeting is provided by dividing the number of output documents (212), by the number of activities (97), i.e. 2.2.

Conclusions

MPEG holds quarterly meetings with an attendance of ~500 experts. If we assume that the average salary of an MPEG expert is 500 $/working day and that every expert stays 6 days (to account for attendance at AhG meetings), the industry investment in attending MPEG meetings is 1.5 M$/meeting or 6 M$/year. Of course, the total investment is more than that and probably in excess of 1B$ a year.

With the meeting organisation described above MPEG tries to get the most out of the industry investment in MPEG standards.

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