International organisation for standardisation

USAC Baseline Profile

In the Baseline USAC Profile the following coding tools shall not be employed:

• 
  Time warped filterbank
  
• 
  DFT based harmonic transposer in enhanced spectral band replication
  
• 
  Fractional delay decorrelator in MPEG Surround for mono to stereo upmixing (MPS212)
  

Level	Max. channels	Max. sampling rate [kHz]	Max. PCU	Max. RCU
1	1	48	5	5
2	2	48	14	10
3	5.1	48	35	28
4	5.1	96	70	28

Discussion:

Max Neuendorg, FhG, noted that the PCU and RCU numbers in the Profile table above are approximate and are intended to indicate peak complexity.

Gregory Pallone, Orange Labs, noted that 2 channels at 96 kHz would be an interesting level. He also noted that there was some discussion at previous MPEG meetings on the topic of changing the name of the USAC specification. The Chair noted that he would be very happy to discuss a different name, and that the best alternatives that he was aware of are:

• 
  eXtended Audio Coding (XAC)
  
• 
  Advanced Broadcast Coder (ABC)
  

Juergen Herre, FhG, noted that higher quality coding at stereo could be satisfied by the HD-AAC Profile, which can deliver 96 kHz sampling at a saleable bit depth.

Kristofer Kjörling, Dolby, noted that at Dolby there were many hours of discussion with staff that were aware of the needs of Dolby customers to determine the selected levels of the USAC Baseline Profile, but that he would be happy to hear about the needs of other customers.

Werner Oomen, Philips, noted that in the Super Audio CD product (Philips/Sony) it was channels the the customer wanted.

It was the consensus of the Audio Subgroup to include the USAC Baseline Profile into the USAC Study on DIS.

A second proposed profile named “HE-AAC V3” was presented. This consists of:

• 
  The HE-AAC V2 profile
  
• 
  The USAC Baseline profile, restricted to Level 2 (i.e. mono or stereo at samplings rates not higher than 48 kHz)
  

The presenter stated that market and industry feedback clearly stated that combining USAC with HE-AAC v2 would significantly increase the probability of success and adoption of USAC in the marketplace. Furthermore, the presenter stated that including Baseline USAC profile level 2 in the HE-AAC v3 profile would provide the AAC family of profiles with the missing functionality of consistently high performance across content types at low bitrates. The presenter further stated that all market and industry feedback the presenter had received clearly stated that including USAC multi-channel in the AAC family, would seriously confuse the marketplace since a new discrete multi-channel coding algorithm would be introduced in the AAC family, but one that has no compelling technical merit. He summed up by stating that it would have no or very limited technical merit, and be clearly counterproductive from a market and industry-need perspective.

Gregory Pallone, Orange Labs, re-stated the position that it does not support the V3 profile because it does not see a technical motivation for the profile.

Masa Nishiguchi, Sony, reported that Sony has an interest in the profile.

Max Neuendorf, FhG, presented

m20066

Proposed amendment to ISO/IEC 14496-3 MPEG-4

Bernhard Grill, Max Neuendorf, Roch Lefebvre, Kristofer Kjörling, Heiko Purnhagen, Werner Oomen,

The contribution proposes an amendment to MPEG-4 Audio (Subpart 1). The purpose is to permit USAC to be carried within the MPEG-4 infrastructure, which includes the MPEG-4 File and MPEG-2 Systems. The amendment defines USAC as audio object type (AOT) 42. (One might assume that this is because USAC is the answer to the question.) Profile and Level Indications are define, and most importantly the AudioSpecificConfig() is modified to add a case statement for AOT 42 (USAC) which then branches to the UsacConfig().

The Chair notes that the discussion on the HE-AAC V3 is ongoing, so that the text in the amendment must reflect the final outcome of that discussion.

It was the consensus of the Audio Subgroup to issue an amendment to MPEG-4 Audio based on the contribution text, with possible modification to reflect the outcome of the discussion on the HE-AAC V3 profile.