Jaroslav Kysela wrote: > > On Thu, 21 Feb 2002, Kai Vehmanen wrote: > > > On Tue, 19 Feb 2002, Jaroslav Kysela wrote: > > > > >> I'm still a bit puzzled why I didn't get xruns in the test case quoted > > >> below, but until I can reproduce the problem, there's not much to discuss > > > You posted this sw params on alsa-devel a few days ago: > > [....] > > > sw_params: > > > stop_threshold: 4294967295 > > [...] > > > As you can see, the stop_threshold is set to UMAX_INT. In case when > > > stop_threshold is above ring buffer size, then it means for drivers: I > > > don't care about xruns, don't report them. The stop threshold must be > > > equal to ring buffer size to get xruns when no more frames are in ring > > > buffer. > > > > Hmm, makes sense. This raises a few new questions: > > > > 1) Is 'avail > stop_threshold' the only condition when a stream > > can move from RUNNING to XRUN state? The only places I located > > in the current source tree, where this state change happens, were > > in alsa-kernel/core/pcm_lib.c, functions > > snd_pcm_update_hw_ptr_interrupt() and snd_pcm_update_hw_ptr(). > > > > 2) If (1) is true, why does runnig jack produces xruns every > > now and then...? The stop_threshold is UMAX_INT for > > both directions and it should never occur that over > > buffer_size samples is writable to, or readable from > > the pcm device. > > > > And to save your time ;), here's one possible explanation to (2): > > > > Looking at jackd code, one possibility is that the we are only getting an > > EPIPE from snd_pcm_avail_update(), but the stream is still in RUNNING > > state. At least in alsa-lib/src/pcm/pcm_hw.c:snd_pcm_hw_avail_update() > > we have a test for: > > > > --cut-- > > if (avail > pcm->buffer_size) > > return -EPIPE; > > --cut-- > > > > This would trigger jackd's xrun handling code, but leave state to RUNNING. > > Am I on the right track here? > > Yes, this condition is faulty. It should be 'avail >= pcm->stop_threshold'. > Fixed in CVS and thanks for verbose error detection.
Perhaps I'm missing something, but I strongly disagree with your recent changes on CVS: - if avail > buffer_size this means either played garbage (playback) or overwritten samples (capture). The return of an error is perfectly sensible (also because the value returned would not have any sensible meaning). - the insertion of SND_PCM_IOCTL_XRUN is a nonsense, as the application has explicitly asked to not stop the stream when xrun happens. As a side note (and as a broken record :-( ), I'd like you don't change the API without peer review. I hope you fully undertstand why... -- Abramo Bagnara mailto:[EMAIL PROTECTED] Opera Unica Phone: +39.546.656023 Via Emilia Interna, 140 48014 Castel Bolognese (RA) - Italy ALSA project http://www.alsa-project.org It sounds good! _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
