[FFmpeg-devel] Flac encoder and MPEG4 ALS

Justin Ruggles justinruggles
Sun Mar 30 14:18:35 CEST 2008

Benjamin Zores wrote:
> Kostya a ?crit :
>> On Sun, Mar 30, 2008 at 03:35:22PM +0000, Jai Menon wrote:
>>> On Sunday 30 March 2008 08:48:52 Benjamin Zores wrote:
>>>> Jai Menon a ?crit :
>>>>> Hi,
>>>>> I started some basic work on the MPEG4 ALS encoder and I get the feeling
>>>>> that I could reuse a lot of code from the flac encoder. So
>>>>> (hypothetically ;-)) if I were to submit a patch, is it okay if I move
>>>>> some code out of flacenc.c to a shared source file?
>>>> IIRC we don't even have a decoder for that atm.
>>>> Do you have a working ffmpeg decoder for that or are you using the
>>>> closed mp4alsRM19 binary ?
>>> Very correct. It would be more sensible to write a decoder for  libavcodec 
>>> before pursuing this. But this "work" on the encoder is with reference to the 
>>> GSoC task. I'm using the RM20 reference decoder and it suits my current 
>>> purpose. Also i think that the encoder would be tested/verified against the 
>>> reference.
>> Just curious - is it possible now to distinguish ALS from ordinary AAC in mp4
>> container without extra hack (i.e. looking into extradata)?  
> Using audio-only, it can be contained in WAVE/AIFF/BWF container with 
> 'A' 'L' 'S' 0x00 FourCC but I can't tell for MP4.

I don't know a lot about MP4 yet.  The object type ID is 36....don't
know if that makes it easy to distinguish.


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