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

Alexander E. Patrakov patrakov at gmail.com
Fri Dec 19 05:36:35 PST 2014

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.

Alexander E. Patrakov

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