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

[Tanu Kaskinen]

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.

-- 
Tanu