[FFmpeg-devel] [PATCH] als in mp4

Alex Converse alex.converse
Mon Mar 23 07:40:35 CET 2009

On Mon, Mar 23, 2009 at 2:29 AM, Baptiste Coudurier
<baptiste.coudurier at gmail.com> wrote:
> Jai Menon wrote:
>> On 3/23/09, Baptiste Coudurier <baptiste.coudurier at gmail.com> wrote:
>>> Jai Menon wrote:
>>> ?>> [...]
>>> ?>>
>>> ?>> When were they initially set to the correct values?
>>> ?>
>>> ?> stsd atom/box? i think
>>> ?>
>>> Hummm, stsd does not contain the correct sample number for everything
>>> ?using 'mp4a' tag. Values are correct in 'esds' box.
>> Which means we should parse the extradata (in this case als specific
>> conf) and get values from there? I can do this for als by maybe adding
>> a new function to mpeg4audio.c.
> I don't know how exactly ALS works, but it might use the
> AudioSpecificConfig like others, this code might belong to mpeg4audio.c,
> yes.

It's set in the AOTSpecificConfig. In this case it is the
ALSSpecificConfig for AAC it is the GASpecificConfig. Both of these
are embedded in the AudioSpecificConfig.

Right now for AAC we just leave it set to zero and the decoder figures
it out just fine.

Rob: care to weigh in?


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