[Mp4-tech] Re:[Audio][Software]: Reference software for MPEG4-AAC

[Ralph Sperschneider]

Umang Garg wrote:
> Dear Members,
>
> The audio reference software available from 
> ftp://mpeg4vm@ftp.tnt.uni-hannover.de/incoming/cvs/ contains two 
> instances of the Audio decoder.  The first instance is the 
> mp4AudVm_Rewrite and the second instance is the mp4mcDec. 
>
> I understand that mp4mcDec is the multi-channel Decoder for MPEG4-AAC 
> while mp4AudVm_Rewrite supports MPEG4-AAC along with other MPEG4 Audio 
> decoders.
>
> (Q1) Does mp4AudVm_Rewrite support multi-channel decode ?

Yes.
>
> (Q2) For MPEG4-AAC, are both the instances of the decoders( 
> mp4AudVm_Rewrite and mp4mcDec) equivalent ?

mp4mcDec support only AAC Main, AAC LC, AAC LC+SBR, AAC SSR and AAC LTP. 
mp4AudVm_Rewrite supports all AAC AOTs.
>
> (Q3) For MPEG4-AAC, are both the instances of the decoders( 
> mp4AudVm_Rewrite and mp4mcDec) updated regularly(in the weekly 
> snapshots) ?

Yes, as far as updates are required.
>
> (Q4) Do both references, mp4AudVm_Rewrite and mp4mcDec, support SBR 
> decoding ?

Yes.
>
> (Q5) For MPEG4-AAC, is there any difference between mp4AudVm_Rewrite 
> and mp4mcDec, that should encourage the usage of one as against the 
> other ?

They should both be fully functional and conform for the AAC AOTs they 
support. mp4mcDec might be easier to understand and to modify, but in 
the MPEG-4 Audio reference software it is available for historic reasons 
only (it does neither support AAC scalable not does it support the ER 
AAC AOTs).
Best regards,
Ralph
-- 
Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 344
Fraunhofer IIS                  | Fax:   +49 9131 776 398
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