[ANNOUNCE] New Mixer Handling in PA 0.9.16/F12

[Michal Hlavinka]

On Wednesday 29 July 2009 15:16:20 Lennart Poettering wrote:
> On Wed, 29.07.09 12:33, Michal Hlavinka (mhlavink at redhat.com) wrote:
> > > This reminds me your note:
> > >
> > >
> > > https://tango.0pointer.de/pipermail/pulseaudio-discuss/2009-July/004519
> > >.htm l
> > >
> > >     PA does not make use of hardware mixing. And I don't plan to change
> > >     that. It's obsolete technology. CPUs these days come with
> > > extensions such as MMX or SSE precisely for speeding up DSP tasks such
> > > as PCM mixing. This is way more flexible that hw mixing, and definitely
> > > the way to the future, both on the desktop and on embedded envs as
> > > well.
> > >
> > >
> > > The "obsolete technology" -- who made this decision? Is it your private
> > > opinion or any suggestion from sound card manufacturers?
> > >
> > > It seems that HW companies still produce the "obsolete technology".
> >
> > First, I like pulseaudio, especially the ability of moving streams from
> > one sink to another is awesome for laptops with external sound card :o)
> >
> > But imo hw mixer (or other hw parts) are not that bad... we still have hw
> > accelerated graphic, math,... why not sound? Also this remains me that
> > pulseaudio eats 24 % of my (1.6GHz) cpu when mapping stereo stream to 5.1
> > which (I suppose) some hw mixer could do while letting cpu free for other
> > tasks.
>
> If PA eats a lot of CPU this can have many reasons, most of them have
> to do with the latency settings requested by the applications  or that
> have been configured due to frequent underruns. However the actual
> mixing is certainly the smallest part of it. Plese don't forget that
> mixing is not exactly the most complex operation on earth.

Well... I'm pretty sure I have no idea how it works :D I've just noticed that 
when playing stereo and sound card (Aureon MK II) is configured for stereo, it 
eats about 4 % and (when speakers are set as 5.1) only front speakers work (as 
expected), when I configure that card for 5.1 output and play stereo stream it 
goes to all 5.1 speakers and eats about 24 % of cpu