On Tue, 2013-02-12 at 10:22 +0100, David Henningsson wrote: > On 02/12/2013 10:02 AM, Tanu Kaskinen wrote: > > On Tue, 2013-02-12 at 08:54 +0100, David Henningsson wrote: > >> On 02/11/2013 11:03 AM, Dmitri Paduchikh wrote: > >>> Hello, > >>> > >>> When I play a sound using paplay (or aplay with ALSA configured to use > >>> PulseAudio) there is a big pause between two successive runs. For > >>> example: > >>> > >>> $ paplay sound1.wav; paplay sound2.wav > >>> > >>> The pause between these sounds is something about two seconds. I've > >>> tried to adjust latency (through --latency-msec=50) but this doesn't > >>> seem to change much. > >>> > >>> Couldn't you explain what is the cause of this pause? Is it possible to > >>> eliminate it? > >>> > >> > >> This is a well-known issue which we discussed briefly at PulseConf. > >> Fixing it is not trivial, unfortunately. > >> > >> I did a quick test here; and for me the delay is 250 - 500 ms, which is > >> consistent with the output of pacmd list-sinks: > >> > >> configured latency: 0.00 ms; range is 0.50 .. 371.52 ms > >> > >> Is your maximum latency going up to about 2000 ms? What distro are you > >> running? > >> > >> There was some effort a while ago to try to increase this to 2000 ms in > >> order to reduce power consumption, and I think we had that in Ubuntu too > >> at some point? I don't know why this is now down to 371 ms, but given > >> that gstreamer has a latency or similar magnitude (200 - 400 ms, IIRC) > >> for media playback anyway, I see little reason to investigate it > >> further. And in addition, it helps a bit against this bug. :-) > > > > In case you didn't know, the maximum hw buffer size for HDA is defined > > by this kernel configuration option: CONFIG_SND_HDA_PREALLOC_SIZE. The > > default is 64 (kB), which results in 271.52 ms with 2 ch, 16 bit, 44.1 > > kHz. > > You probably meant 371.52 (not 271.25), or are we calculating differently? My mistake. > > It is recommended to change this value to e.g. 2048 on systems that > > use PulseAudio. Since Debian still doesn't enable PulseAudio by default, > > Debian's kernel uses the default value. Perhaps that has propagated to > > Ubuntu by accident at some point? > > No, Ubuntu has its own kernel packaging, unrelated of Debian's. But > upstream also has 64 as default. > But, given the fact that this bug gets worse with a larger prealloc > size, and the gstreamer still doesn't use more than ~200 ms latency > anyway, should we really recommend this change of prealloc_size? Perhaps not. I would, however, recommend the change for PulseAudio developers. It helps with noticing bugs. -- Tanu
