[FFmpeg-devel] suggestion for expanding audio bitdepth support in libav/ffmpeg

[Benjamin Larsson]

madshi wrote:
> I've been told by different people that sooner or later ffmpeg is supposed
> to get support for multiple audio bitdepths with all the bells and whistles.
> But it seems to be a very big change and so it gets pushed back, 
> respectively
> nobody is daring to take over this job. Please correct me, if I'm wrong 
> on this.
> 
> Here comes a suggestion on a first step to the final goal which should be
> much easier to realize without breaking anything:
> 
> --------
> 
> CURRENT STATE:
> As far as I understand things, currently ffmpeg calls the audio decoders
> and expects 16bit integer samples from them. Other formats are not
> supported by ffmpeg.
> 
> ULTIMATE SOLUTION:
> ffmpeg can handle any audio format and every decoder can output what
> it wants.
> 
> INTERMEDIATE STEP:
> We let the decoders output whatever they want but add an intermediate
> step between the decoders and ffmpeg which converts every audio
> format to 16bit integer. This way ffmpeg can stay as it is. And the
> decoders can in the beginning also stay as they are without breaking
> anything. But this would allow us to change one decoder after the other
> to output the most optimal sample format and bitdepth without having
> any effect on ffmpeg. Furthermore if there is a central audio conversion
> routine to 16bit integer, it would also be rather easy to add proper
> TPDF dithering, which is missing right now, I believe.
> 
> --------
> 
> What do you guys think?
> 
> I have to add that I'm not up to the task of doing the work. I just wanted
> to throw my thoughts at you.
> 
> madshi.

We have this page to collect our ideas. I've been focusing on audio mixing.

http://wiki.multimedia.cx/index.php?title=FFmpeg_audio_API

Anyway regarding the audio output from the codecs. The plan is to let
all codecs output in the native format and if it is float also support
the fast float format.

MvH
Benjamin Larsson