[pulseaudio-discuss] GSoC Proposal: Resampling Improvements

Tanu Kaskinen tanu.kaskinen at intel.com
Fri Apr 19 09:48:36 PDT 2013

On Thu, 2013-04-18 at 15:26 +0200, Damir Jelić wrote:
> Hi.
> For those who don't know, I'm Damir Jelić from Croatia and I would like to
> work on the "Resampling Improvements" project during this year's Summer of
> Code.
> Last year I participated and finished the "Latency offset" project. After
> the summer I tried to become a regular contributor. For those who are
> interested, all my contributions can be seen in the git log [1].
> I know I said that last year should be my final year as a student but I
> prolonged my studies for a year and I'm still eligible for this year's
> Summer of Code.
> I picked this project because it's a part of pulseaudio that I consider
> quite interesting and didn't had the chance to touch yet.
> I have some DSP background (although more from control theory than from
> digital audio) and also I have some assembly background, but not from any
> modern instruction set (z80), which should make me a good candidate for this
> project.
> 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.

> 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.


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