> > > > PCM Devices which have the BATCH flag set update the PCM pointer > only with > > period size granularity. Using timer based scheduling does not have > any > > advantage in this mode. For one devices which have that flag set > usually > > update > > the position pointer in software after getting the period interrupt. > So > > disabling the period interrupt is not possible for this kind of > devices. > > Furthermore writing to or reading from the buffer slice for the > current > > period > > is not possible since the position inside the buffer is not known. On > > the other > > hand the tsched algorithm seems to get easily confused for this kind > of > > hardware, which results in garbled audio output. This typically means > > that timer > > based scheduling needs to be manually disabled on systems with such > devices. > > Auto disabling tsched in this case allows these systems to run with > the > > default > > configuration. > > > > > > If the playback position is reported in steps instead of monotonic > increasing ? > > > > does this mean that you also need to increase rewind_safeguard to one > period > > or modifiy snd_pcm_rewindable ? > > > Yes that makes sense. The safeguard should probably be 1.5 periods or 1 > period + fixed value, since it will always take some time from when the > hardware reaches the next period to when userspace is notified about this. > > I'm unfortunately not that familiar with pulseaudio. Maybe there is a > better > way to fix this problem then to disable tsched. If anybody wants to > recreate > the issue it can easily be emulated by applying the following patch to your > kernel: > > does all alsa drivers with SNDRV_PCM_INFO_PATCH update the playback/capture position in period interrupt ? usb-audio seem update when each URB send/receive (in 1ms intervals) ymfpci driver also update hwptr in 5ms interval but no SNDRV_PCM_INFO_PATCH and no constraint in period time must be interval of 5 ms the rewind_safeguard is affected by the size of FIFO buffer as you cannot rewind any data in FIFO buffer of DSP/ sound controller -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.freedesktop.org/archives/pulseaudio-discuss/attachments/20131203/6311a91d/attachment-0001.html>
