International organisation for standardisation

2.3Creation of Task Groups

Task groups were convened for the duration of the MPEG meeting, as shown in . Results of task group activities are reported below.

2.4Approval of previous meeting report

The Chair asked for approval of the 96^th Audio Subgroup meeting report, which was registered as a contribution. The report was approved.

m20455

96th MPEG Report

S. R. Quackenbush

2.5Review of AHG reports

There were no requests to review any of the AHG reports.

2.6Joint meetings

Groups	What	Where	Day	Time
S, A, V	Reference Software SVN	3	Tue	1400-1500
R, A	Future Audio	Audio	Wed	1200-1300
R, S. A. V	MPEG-H Vision	Req	Wed	1400-1800
R, A	USAC Profiles	Audio	Thu	1000-1100

2.7Received National Body Comments and Liaison matters

No.	Title	Source	Responding
M21389	FRNB comment on MPEG Profiles	Pierrick Philippe on behalf of the French National Body	S. Quackenbush
m20311	Liaison Statement from ITU-R SG 6	ITU-R SG 6 via SC 29 Secretariat	S. Quackenbush
m20391	Liaison Statement from ITU-R SG 6/WP 6B	Unified Speech and Audio Coding	S. Quackenbush
m20396	IEC CDV 62731: Text-to-Speech for Television -- General Requirements	IEC TC 100 via SC 29 Secretariat	S. Quackenbush

2.8Plenary Discussions

There were none.

3Record of AhG meetings

There were no AhG meetings.

4Task group activities

4.1Joint Meeting

4.1.1With Requirements on Audio for HEVC (Wed 1200-1300)

Akio Ando, NHK, presented

m21114

Further requirements for HEVC audio from viewpoint of broadcasting

Akio Ando

The contribution reviewed NHK studies of 3D audio presentation:

• 
  22.2 Theatre style
  
• 
  10.1 Home theatre style
  
• 
  5.1 Home theatre style
  
• 
  Stereo
  

They have also investigated Wave Field Synthesis (WFS), using loudspeakers integrated into the frame of the video display. WFS uses HRTF with cross-talk cancellation. In one case there were more than 100 loudspeakers arranged around the edge of the video display, in another case there were only three loudspeakers under the video display.

A major issue in having such audio-visual setups in the home are how to transmit the audio program required for the 3D audio presentation.

The presenter noted that not all programs will be available in 3D formats – some will be 5.1 and some stereo, so there is a need to transition from one format to another (e.g. during a short program insert). The contribution proposes to means to do this:

• 
  Simulcast. All of the 22.2, 10.1, 5.1 and stereo programs are coded and transmitted. This would require some additional bitrate as compared to only a 22.2 channel program.
  
• 
  Channel matrixing. Some format is transmitted from which all presentation formats can be derived. This may require very careful control of quantization noise so that it is masked for all presentation formats.
  

Finally, it proposed to add two requirements to the “Audio for HEVC” document.

• 
  For simultaneous transmission, a perceptually transparent audio coder should be more efficient.
  
• 
  For scalable transmission, a perceptually transparent audio coder should be robust to the “matrix” operation.
  

Juergen Herre, FhG, noted that “matrix” coding can be very difficult in that it may be that after matrixing the desired signal is cancelled but the undesired quantization noise is not cancelled. Correcting this may require a bit rate equivalent to simulcast. Werner Oomen, Philips, noted that MPEG Surround in an example of solving the “upmix” problem with a new technology.

Juergen Herre, FhG, presented

m21247

Thoughts on Audio for High Efficiency Video Coding

Juergen Herre, Andreas Silzle

The contribution presented three categorizations of technology for 3D audio recording and presentation:

• 
  Channel-based
  
• 
  Object-based
  
• 
  Scene-based.
  

For the scene-based case, examples are Ambisonics (B-Format or Higher Order Ambisonics). There are some low-bitrate versions, e.g. Spatial Audio Scene Coding (SASC) and Directional Audio Coding (DirAC). Note that ambiance (room or environmental) is captured in the recording. It also allows some interactivity, such as scene rotation and “acoustic zoom.” The latter may permit the user to adjust the audio scene width to match video scene width.

The contribution contains a table similar to what is found in the “Audio for HEVC” document, but with additional information for scene-based coding.

The presenter reviewed what is needed for a new format or standard to be successful in the marketplance. These include

• 
  Production. Success requires that the format be adopted into the normal production workflow.
  
• 
  Transmission. This is MPEG’s normal home. Higher compression lowers transmission cost, which promotes adoption.
  
• 
  Reproduction. This is the problem raised by the previous contribution. A flexible and high-quality solution means that a larger user base will use the format.
  

The contribution includes a table that adds detail to these three topics.

Discussion

It was agreed to have a break-out group to incorporated the suggested changes into the “Audio for HEVC” document.

After the break-out meeting was held and the edited document reviewed, Gregory Pallone, Orange Labs, expressed had a concern about the words "with low to moderate complexity" present in two bullets of the "possible requirements" paragraph of the document and proposed to replace it by "possibly with low to moderate complexity" since some devices, which may be limited by the rendering system (few loudspeakers) or the network bandwidth (low bandwidth), may not be limited by the processing power (powerful PC at home). He said that even if in the general case in which lower the complexity is always better, he thinks that this restriction is useless here. He added that it could appear as a new requirement and that the different limitations should then be addressed separately, for example:

• 
  "Transcoding for low bandwidth devices"
  
• 
  "Transcoding for low complexity devices"
  
• 
  "Transcoding for low rendering capabilities devices"
  

The Chair responded by urging interested experts to bring edited versions of the document as contributions to the next meeting as a means to share thoughts and better progress the document.

The name was changed to "Thoughts on 3D-Audio" and the document was approved as an output from Audio.