[pulseaudio-discuss] [PATCH] loopback: Always use the trivial resampler.

[Tanu Kaskinen]

On Thu, 2011-03-24 at 09:09 -0500, pl bossart wrote:
> > The sink may be running in a low-latency mode even if the loopback
> > stream doesn't have any latency requirements - there may be other
> > streams active at the same time with stricter timing requirements.
> >
> > FWIW, the practical case here was a very simple test of looping null
> > sink's monitor to a hw sink with default settings on Harmattan. It may
> > be that our setup is more suspectible to this kind of problems than
> > "normal" systems, but I still think that non-realtime-safe stuff should
> > be kept out of the IO threads, regardless of the setup, especially if
> > such stuff can very well be done outside the IO thread.
> 
> if you are still using 10ms periods on the hw sinks, then yes it's an
> artifical use case in a constrained environment that doesn't use
> timer-based scheduling...
> I don't disagree that doing SRC in an io thread is not that kosher,
> but keep in mind that we also do mixing and volume control in the IO
> thread. There is some amount of DSP in this thread which will impact
> response time to hw events.

It might be that you have misunderstood the reason for the patch. Now
that I read the patch description again, it indeed isn't entirely clear:
the problem that I'm having is that the periodic (every 10 seconds)
reinitialization of the resampler takes too much CPU time. The
resampling itself is fine - I don't think it's even possible to move
that out of the IO thread, or if it's possible, it probably wouldn't
bring any benefits.

-- 
Tanu