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

Tanu Kaskinen tanu.kaskinen at linux.intel.com
Wed Mar 11 12:32:21 PDT 2015

On Wed, 2015-03-11 at 22:07 +0300, Andrey Semashev wrote:
> On Wednesday 11 March 2015 20:48:11 you wrote:
> > On Wed, 2015-03-11 at 20:27 +0200, Tanu Kaskinen wrote:
> > > 
> > > 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/
> Technically, "up to 20 ms" is not correct because sometimes the delay may be 
> higher. I was careful about that when I updated the man pages.

Sorry, when I read "usually up to around 20 ms, in rare cases more" in
the man page, I dropped the word "more" in my mind, so I thought 20 ms
was a rare case. I'll correct the wiki page.

> Regarding hq vs vhq, I think I mentioned it somewhere, vhq does computation 
> with more precision bits than hq, so it mostly targeted for high bit depth 
> formats. Whether or not the difference is audible and under what conditions is 
> an other question. I did some performance measurements, they are given on the 
> page I referenced earlier [1].

I guess this is mainly a comment on this sentence: "We don't know what
evidence the libsoxr developers base their recommendation on." I'll try
to choose a more careful wording.

Thanks for your input!


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