[pulseaudio-discuss] Playback pauses

[Tanu Kaskinen]

On Tue, 2013-02-12 at 22:52 +0600, Dmitri Paduchikh wrote:
> Hmm, in my case the upper bound in this range is 1837,50 ms. May be this
> explains huge pauses. Though I'd expect that command-line option
> --latency-msec=50 should change the used latency.

The reason why that doesn't work is probably that when the last byte of
the stream buffer is copied to the sink buffer, the sink latency is set
back to about 2 seconds, but the stream is not considered yet finished,
because the data is still in the sink buffer, not yet out of the
speakers. Thus, there will be roughly 2 seconds before the sink requests
more data, and this is the event that triggers the notification that the
stream has now definitely finished.

> Is the maximal value
> configurable or is only calculated from the buffer size in kernel?

It's configurable, to some extent. By default, the alsa modules are
loaded by module-udev-detect. You can't configure the maximum latency if
you use module-udev-detect (there's no reason why it couldn't be
configurable also in that case, but there just hasn't been need for
implementing that). If you don't use sound card hotplugging,
module-udev-detect is not necessary. You can comment out
module-udev-detect loading in /etc/pulse/default.pa, and replace it with
this command (or several similar ones, if you have multiple sound
cards):

load-module module-alsa-card device_id=0 tsched_buffer_size=65536

The device_id parameter is the sound card index, as listed
in /proc/asound/cards. The tsched_buffer_size parameter is the sink
buffer size in bytes, which determines the maximum latency, and which
you can choose freely. The kernel configuration determines the upper
bound. 65536 matches the default kernel configuration of 64 kilobytes.

-- 
Tanu