09.06.2015 11:27, Arun Raghavan wrote: > > > On 09-Jun-2015 11:26 am, "Raymond Yau" <superquad.vortex2 at gmail.com > <mailto:superquad.vortex2 at gmail.com>> wrote: > > > > >> > > >> > > >> > > > >> > below is what the terminate shows when running pcm_avail.c > > >> > > > >> > uid=0 gid=1007 at nutshell:/ # alsactl_test > > >> > min_period_size: 8 frames, dir: 0 > > >> > Playback hwparams: FIFO size is 8 > > >> > Hardware PCM card 0 'rsnd-dai.0-dirana3.0' device 0 subdevice 0 > > >> > Its setup is: > > >> > stream : PLAYBACK > > >> > access : RW_INTERLEAVED > > >> > format : S16_LE > > >> > subformat : STD > > >> > channels : 2 > > >> > rate : 48000 > > >> > exact rate : 48000 (48000/1) > > >> > msbits : 16 > > >> > buffer_size : 4096 > > >> > period_size : 1024 > > >> > period_time : 21333 > > >> > tstamp_mode : NONE > > >> > period_step : 1 > > >> > avail_min : 1024 > > >> > period_event : 0 > > >> > start_threshold : 1024 > > >> > stop_threshold : 4096 > > >> > silence_threshold: 0 > > >> > silence_size : 0 > > >> > boundary : 1073741824 > > >> > appl_ptr : 0 > > >> > hw_ptr : 0 > > >> > Playing silence > > >> > Available: 0, loop iteration: 0 > > >> > Available: 1024, loop iteration: 1469 > > >> > Available: 2048, loop iteration: 5609 > > >> > Available: 3072, loop iteration: 9667 > > >> > > > >> > All I got is just the 4 lines. > > >> > > >> If your sound card only increment hw_ptr only at interrupt occur, you > > >> need to increase default_rewind_safeguard from 256 bytes to your > > >> selected period size > > > > > > > > > No. PulseAudio, in timer-scheduling mode, does not use periods at > all. You need to change the driver so that it reports > SNDRV_PCM_INFO_BATCH, so that PulseAudio does not try to use this mode. > > > > > > > > >> > > >> This mean that your sound card won't work with timer scheduling or > > >> dynamic latency, you can only archieve low latency by decrease > period size > > >> Why do pulseaudio enable timer scheduling when most sound card > use IRQ ? > > > > > > > > > Because most broken sound cards driver authors forget to report > SNDRV_PCM_INFO_BATCH? > > > > Why pulseaudio rely on the flag if your program can find out the > granulatity ? > > AFAIK, there isn't a way to figure out granularity. Having this would > be nice as we could be more intelligent about our tsched behaviour. > There is not only no way to query granularity, in some cases it is simply unknown. As for my approach (of measuring it directly), I currently think (but do not insist) that it is not suitable for inclusion into PulseAudio, because it is based on using a silent "test sound", busy-looping and repeatedly querying the position until it plays out. This would be unreliable if there is an unrelated CPU usage spike, and I think that busy-looping in general is not welcome. -- Alexander E. Patrakov -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.freedesktop.org/archives/pulseaudio-discuss/attachments/20150609/e36bdcc1/attachment.html>
