[FFmpeg-devel] Flac encoder and MPEG4 ALS

Kostya kostya.shishkov
Sun Mar 30 15:24:25 CEST 2008

On Sun, Mar 30, 2008 at 08:34:18AM -0400, Justin Ruggles wrote:
> 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.
> A decoder, in this case, is a much larger task since ALS has several
> different optional extensions that would have to be supported.  If you
> feel that you are up to the task, by all means submit a proposal.  I
> chose to suggest an encoder because it is more flexible as far as the
> timeframe, and therefore much more likely to make it to SVN by the end
> of the summer.

I've looked at it once. Seems the most features are for floating-point
mode, baseline decoder should be comparatively easy. Especially if you
are the person who writes encoder to it ;)

Too bad the spec costs money and available drafts allow you to write
some hybrid between LPAC and ALS. At least we have the reference
decoder and encoder sources.
> > I have submitted what i hope will be the final patch for my qual task. Once 
> > that is done i'll have time to maybe get a basic als decoder and some code 
> > refactoring done. Also there is that TAK reversing thing.......... ;-)
> I agree with Kostya that we should not try to reverse-engineer TAK.
> -Justin

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