Organisation internationale de normalisation

Part 3 – Specification
Study on 14496-3:AMD3/DCOR2
Part 4 – Conformance	14496-26/Dcor x (Audio Conformance), to issue at the next meeting
Part 5 – Reference software	14496-5:AMD10/Dcor 3, to issue at this meeting

Ralf Geiger, FhG, presented

m15865

Further information on the complexity of the HD-AAC profile

Ralf Geiger Virgilio Bacigalupo

This contribution reported on computation complexity and compression performance of the CBAC tool in MPEG-4 SLS. As an overall average, it reports that CBAC tool delivers an additional 0.2% of compression performance and requires an additional computational complexity of 10%. It concludes that in considering compression / complexity trade-off for selecting tools to put in the HD-AAC profile, it recommends that the CBAC tool not be included in the profile.

It was the consensus of the Audio Subgroup to split the current working draft on ALS and SLS profile in two, leave the ALS profile at WD and promote the SLS profile to CD at this meeting. The tools in the SLS profile will remain unchanged, specifically the CBAC tool is not included in the HD-AAC profile.

Kristofer Kjörling, Dolby, presented

m15877

proposed new restriction for the AAC family of profiles and proposed new profile

Andreas Schneider Kristofer Kjörling

The contribution notes that the vast majority of AAC, HE-AAC and HE-AAC V2 profile implementations only support 1024 block length. The systems that mandate a 960 block length in the bitstreams are DAB+ (HE-AAC V2 restricted to 960 block length) and DRM (Scalable AAC with ER syntax and a 960 block length in combination with SBR and two different versions of parametric stereo). In this respect, only DAB+ has the realistic possibility of interoperating with HE-AAC V2 profile decoders.

Concerning the block length issue, the contribution recommends to

• 
  Create a new HE-AAC V2 profile that is restricted to 960 block length
  
• 
  Change the current family of AAC profiles to restricted them to 1024 block length
  

In addition, it recommends moving the non baseline PS to level 5 in the HE-AAC V2 profile.

It was the consensus of the Audio subgroup to incorporate PS issue into the Study on AMD 2/COR 4 HE-AAC V2 Profile.

The Chair presented the following Liaison statements

m15908	Liaison Statement from the Digital Radio Mondiale Consortium to WG 11	Proposal to remove 960 transform from the AAC, HE AAC and HE AAC v2 profiles
m15916	Liaison Statement from "ETSI/EBU/CENELEC JTC on Broadcast"	on 960 frame length in the MPEG-4 AAC family of profiles
m15919	Audio Liaison Statement from WorldDMB Forum WorldDMB Forum via SC 29 Secretariat	on Proposal to remove 960 transform from the AAC, HE AAC and HE AAC v2 profiles

All contributions raise the legitimate concern that MPEG should not remove support for the 960 block length for the AAC family of profiles.