[pulseaudio-discuss] [PATCH 0/4] Add support for libsoxr resampler

[Tanu Kaskinen]

On Wed, 2015-03-11 at 20:27 +0200, Tanu Kaskinen wrote:
> On Wed, 2014-11-12 at 23:16 +0300, Andrey Semashev wrote:
> > On Wednesday 12 November 2014 20:03:48 Alexander E. Patrakov wrote:
> > > 12.11.2014 14:26, Alexander E. Patrakov пишет:
> > > > I will recheck the quality separately later today, in order to verify
> > > > that it is still as good as in the previous tests. Please don't merge
> > > > the patches until this is done.
> > > 
> > > Done. The -mq, -hq and -vhq variants of the resampler never produce
> > > audible distortions. The -lq variant sometimes does, by means of
> > > suppressing very high frequencies, but this is relevant to artificial
> > > tests only, and only if the listener knows that these frequencies are
> > > supposed to be there. Thus, quality is on par with speex-float-5, the
> > > CPU consumption is even better than with speex-float-1. Conclusion:
> > > 
> > > *** the patches are generally acceptable ***
> > 
> > Great! And thanks a lot for the quality data and information. I will send v2 
> > patches in a day or two.
> > 
> > > However, because the low-quality and high-quality versions eat very
> > > similar amount of CPU time, I'd just expose a single (high or very high)
> > > quality setting.
> > 
> > Given that -lq is actually slower than -mq in some cases and has worse 
> > quality, I agree there is no point in keeping it.
> > 
> > However, the other three presets do have different performance and quality. In 
> > my test results [1] -mq is about 2 times faster than -vhq, and -hq is 
> > somewhere in between. Performance wise, there should be no problem with -vhq 
> > on modern CPUs, but maybe the little extra would be desired in embedded domain 
> > to conserve battery. Do you think we could keep the three presets: -mq, -hq 
> > and -vhq?
> > 
> > [1]: http://lastique.github.io/src_test/
> 
> I'm writing release notes for 7.0, and I'm wondering how to describe the
> three soxr resampler variants. Alexander says that all variants are
> perfect quality-wise (no audible distortions). Alexander also says that
> each variant takes about the same amount of CPU time, but Andrey says
> that there's 2x difference between mq and vhq. Who's right?
> 
> To me it sounds like the hq and vhq variants are redundant, since mq is
> at least as fast (and on some hardware significantly faster) as the
> other variants, and there's no meaningful difference in quality.

I now wrote something to the notes, feel free to comment if you'd like
to change something:
http://www.freedesktop.org/wiki/Software/PulseAudio/Notes/7.0/

By the way, the fact that I'm writing the release notes already now
doesn't mean that the release is going to happen any time soon... I'm
just experimenting with a different approach to writing the notes; I'm
trying to avoid a situation where I have to go through the whole commit
history in one go when the release is about to happen.

-- 
Tanu