> > > How accurate are the hwptr playback/capture position ? >> >> >> e,g, USB audio send in URB packet >> >> the position is only updated in one ms > > > There is a chance to update the position every 2 msec. But it differ depending on sampling rate, size of period and streaming mode. > Do you mean the card have internal memory of FIFO to hold 1 packet of data ? Can the driver run with one periods per buffer or need two or more periods ? Why periods_min = 1 ? http://www.freedesktop.org/wiki/Software/PulseAudio/Backends/ALSA/BrokenDrivers/ > > >> Do you mean firewire driver 's pcm_pointer callback does not report >> playback/capture positon in realtime ? > > > Within the 2 msec, I mean it. > > >> there is alway one packet 's uncertainty > > > > > are the any minimum size of the packet ? > > > > e.g. usb audio send in urb > > There is uncertainty. But not one packet. > > Every 2 msec, the drivers queue some packets for transferring. So uncertainty is the number of the packets. > > Currently this number is fixed by 16. See 'INTERRUPT_INTERVAL' macro in 'amdtp.c'. > (In IEE1394, 8000 packets are transferred per sec. So 16 packets equal 2 msec.) > > Do the driver need to use larger value for pulseaudio's rewind_safeguard as it use more channels than the other cards ? https://bugs.freedesktop.org/show_bug.cgi?id=72396 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.freedesktop.org/archives/pulseaudio-discuss/attachments/20140129/a32f0991/attachment.html>
