[pulseaudio-discuss] Why tsched disabled when I use module-alsa-sink with 'mmap=0 tsched=1' parameters?

[Tanu Kaskinen]

On Fri, 2014-12-19 at 18:36 +0500, Alexander E. Patrakov wrote:
> 19.12.2014 18:15, Tanu Kaskinen wrote:
> > On Thu, 2014-12-11 at 21:49 +0900, 김정연 wrote:
> >> Dear developers,
> >>
> >>
> >> I have question something about selecting logic between timer-based
> >> and IRQ scheduling.
> >>
> >> When I tried to load 'module-alsa-sink' with 'mmap=0 tsched=1'
> >> parameters, tsched(timer-based scheduling) becomes disabled by below
> >> codes.
> >>
> >> It seems tsched is allowed only mmap supported ALSA devices. Why
> >> tsched disabled while use non-mmap driven ALSA?
> >
> > Because rewinding is not available in non-mmap mode. That is, it's not
> > possible to rewrite previously written data in non-mmap mode. In
> > timer-based scheduling mode PulseAudio uses bigger buffer size, which
> > causes problems if rewinding isn't available.
> 
> Sorry, rewinding is actually available in non-mmap mode. And, pulseaudio 
> can rewind even without tsched (i.e., tsched == 0 does not imply 
> max_rewind == 0). So the reasoning must be different. But I don't know 
> the answer.

Thanks for the correction. I don't have an alternative theory either.

-- 
Tanu