[Ffmpeg-devel] Dubious field in AAC-ADTS

Nico Sabbi nsabbi
Fri Jun 10 18:28:53 CEST 2005

>-- Original Message --
>To: FFMpeg development discussions and patches <ffmpeg-devel at mplayerhq.hu>
>Subject: Re: [Ffmpeg-devel] Dubious field in AAC-ADTS
>From: M?ns Rullg?rd <mru at inprovide.com>
>Date: Fri, 10 Jun 2005 18:19:03 +0200
>Reply-To: FFMpeg development discussions and patches <ffmpeg-devel at mplayerhq.hu>
>"Nico Sabbi" <nsabbi at fastwebnet.it> writes:
>> Hi,
>> I don't fully understand what's the meaning of the field 
>> "no_raw_data_blocks_in_frame" described here:
>> http://www.audiocoding.com/modules/wiki/?page=ADTS
>> Is it the number of audio frames carried in the current 
>> ADTS packet or what else? If not, can I always assume that
>> an ADTS packets always carries exactly 1 AAC frame?
>That field specifies the number of raw_data_block elements that
>follow.  Each raw_data_block decodes into 1024 or 960 samples for each
>channel.  See ISO 14496-3, section 4.5.2.  Does this answer your
>M?ns Rullg?rd
>mru at inprovide.com

yes: crystal-clear as usual :)

BTW, in the sources of libfaad2 there's a comment stating that
a the 2-bits field present in the specs of ADTS-4 (emphasis
IIRC) but not in ADTS-2 were removed 
from the specs of ADTS-4, effectively making the two frames 
syntaxes identical, except for the ID field. 
Did you ever find some sample coded with 'emphasis'?


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