International organisation for standardisation organisation internationale de normalisation

960/1024 frame length discussion

Kristofer Kjörling, Dolby, presented

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  Define a new profile “Common AAC Profile” (which is equivalent to what is currently HE-AAC v2)
  
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  For three existing profiles (…). “Streams conforming to this profile shall not used the 960 length MDCT transform. For maximum interoperability decoders should support the Common AAC Profile in preference to this profile.
  

The Chair will seek guidance from the Convenor as to whether the planned actions are appropriate. Kristofer Kjörling, Dolby, will bring additional information concerning which fielded products explicitly claim conformance to one of the family of MPEG-4 AAC profiles and the whether the fielded products using AAC or HE-AAC technology support both block lengths.

Andreas Schneider, Dolby, presented

m16315

proposed clarification on byte alignments in LOAS streams

Toshiyuki Nomura

The contribution notes that MPEG-4 defines two functions for byte alignment:

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  ByteAlign()
  
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  byte_alignment()
  

It is very desirable that

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  there be only one function for byte alignment
  
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  that it is unambiguous which bit is the reference bit for byte alignment
  
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  that what is specified in the textual description is the same as what is implemented in the reference source code
  

The contribution proposes to issue a DCOR against MPEG-4 Audio to

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  byte align to the first bit in the raw data block
  
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  use only one function to do so
  

The contribution proposes to issue a DCOR against MPEG-4 Reference Software to

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  align software to text
  

It was the consensus of the Audio Subgroup to DCOR against MPEG-4 Audio and to incorporate any needed changes to MPEG-4 Reference Software into ISO/IEC 14496-5:2001/FDAM 24, MPEG-4 AAC ELD.