<html> <head> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> </head> <body bgcolor="#FFFFFF" text="#000000"> 09.06.2015 11:27, Arun Raghavan wrote: <blockquote cite="mid:CACuU-+h9LKBaq4=e9ev2+cm_LdbMHYR8MhLjAsQNzFNrtyvU6A@mail.gmail.com" type="cite"> On 09-Jun-2015 11:26 am, "Raymond Yau" <<a moz-do-not-send="true" href="mailto:superquad.vortex2@gmail.com">superquad.vortex2@gmail.com</a>> wrote: > > >> > >> > >> > > >> > below is what the terminate shows when running pcm_avail.c > >> > > >> > uid=0 gid=1007@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. </blockquote> 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 </body> </html>