[FFmpeg-devel] Flac encoder and MPEG4 ALS

Benjamin Zores ben
Sun Mar 30 13:28:53 CEST 2008

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.


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