[FFmpeg-devel] [PATCH] als in mp4

[Jai Menon]

On 3/23/09, Alex Converse <alex.converse at gmail.com> wrote:
> 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.

That is fine by me too, the decoder can do this at init. But i doubt
whether streamcopy will work correctly in the absence of a decoder.
If it is too much of a hack, we can just add the codec id to the aot
table and and leave it at that. ffmpeg -i will report wrong channel
count though.

[...]

-- 
Regards,

Jai