[alsa-devel] hw_ptr accuracy with intel8x0 -> PulseAudio issue

[pl bossart]

Takashi,
I tested with .periods_min=2 and reduced the period_max by half. The
underruns reported by PulseAudio are no longer present with this
modification.
However, there's still something fishy here. In both cases, with 1 or
2 periods, PulseAudio seems to wake-up more often than it should with
snd_pcm_poll_descriptors_revents returning a null event. See the
sequence below. Not sure if the problem is a bad configuration of the
timers of if the driver generates these events?
I also noticed that the underrun reported with a single period are
associated with the POLLOUT revent. I am not sure this is normal?
Thanks for your feedback.
- Pierre

D: alsa-sink.c: Waking up in 157.78ms (system clock).
>> WAKEUP
E: alsa-sink.c: snd_pcm_poll_descriptors_revents() returned zero
D: alsa-sink.c: Loop
D: alsa-sink.c: Buffer time: 371 ms; Sleep time: 321 ms; Process time: 50 ms
D: alsa-sink.c: avail: 1076 (samples 269)
>> This is not consistent, there are too few samples in the buffer
D: alsa-sink.c: 365.42 ms left to play; inc threshold = 0.00 ms; dec
threshold = 100.00 ms
D: alsa-sink.c: Not filling up, because too early.
>> go back to sleep
D: alsa-sink.c: Waking up in 157.71ms (system clock).
>> WAKEUP
E: alsa-sink.c: snd_pcm_poll_descriptors_revents() returned zero
D: alsa-sink.c: Loop
D: alsa-sink.c: Buffer time: 371 ms; Sleep time: 321 ms; Process time: 50 ms
D: alsa-sink.c: avail: 1136 (samples 284)
>> again the buffer is still almost full and we have nothing to do
D: alsa-sink.c: 365.08 ms left to play; inc threshold = 0.00 ms; dec
threshold = 100.00 ms
D: alsa-sink.c: Not filling up, because too early.