[pulseaudio-discuss] GSoC Proposal: Resampling Improvements

[Damir Jelić]

Hi Peter.

On Sun, Apr 21, 2013 at 08:31:18PM +0200, Peter Meerwald wrote:
> Hello,
> 
> > > > > What I would like to do over the summer:
> > > > >     - enable resampling with libav
> > > > >     - write some test coverage for the libav resampling method
> > > > >     - deprecate the ffmpeg resample method
> > > > >     - update the speex resample method
> 
> > > > > The ideas page mentions also libresample, if I'm not mistaken pulseaudio
> > > > > already supports resampling via libresample and I'm not sure what would I
> > > > > need to do about this.
> > > > 
> > > > By "libresample", I guess you mean "libsamplerate". Peter can correct me
> > > > if I'm intepreting him wrong, but my understanding is that libsamplerate
> > > > was only mentioned as an example of a resampler with a problematic
> > > > license. I don't know either what should be done about it - perhaps the
> > > > idea was to compare the different resamplers, and if it turns out that
> > > > we don't have any good reason to keep using libsamplerate, we could drop
> > > > that code.
> 
> libsamplerate was mentioned because of the GPL license;
> to work around, a loadable module interface could be offered, so the user 
> can decide
> 

This sounds like a lot of complexity for little gain. What is wrong with
compile time switches/options?

> > > > > Speex has been obsoleted [2] and the resampler seems to had been moved to
> > > > > opus-tools. There are some interesting commits [3] inside this repo and I think
> > > > > it would be nice to update our speex resample method although I'm not sure
> > > > > if it's ok to drop speex and replace it with opus-tools just like that.
> 
> > > > To me replacing the speex resampler with the opus-tools resampler sounds
> > > > like an obvious thing to do, if the upstream says that the speex
> > > > resampler code is deprecated in favour of opus-tools.
> 
> yeah, there seem to be interesting fixes/improvements
> 
> p.
> 
> -- 
> 
> Peter Meerwald
> +43-664-2444418 (mobile)

By the way is there some explicit reason you have chosen libav for this
project? 

FFmpeg now also has a resampling library [1] and I found an interesting
blog post about "ffmpeg vs libav" [2].

Maybe we should support both so different distributions can choose what
to use depending on the default lib they are using.

[1] http://ffmpeg.org/doxygen/trunk/group__lswr.html
[2] http://aballier.wordpress.com/2013/01/18/ffmpeg-vs-libav-a-distribution-maintainer-point-of-view-almost-two-years-after-the-split/