[Bug 29294] No sound with ALSA loopback devices

[wine-bugs at winehq.org]

http://bugs.winehq.org/show_bug.cgi?id=29294

--- Comment #38 from Jörg Höhle <hoehle at users.sourceforge.net> 2012-03-09 12:16:00 CST ---
James, what was the sound experience while running the tests?
Judging from the render log, I'd say:
 - no stuttering, however
 - one underrun every 5 seconds from clock skew. The CreateTimerQueue
   stabilisator patch will help here (but not eliminate it entirely).
   That causes an audible glitch every time.

Every underrun costs 50ms or more, for unknown reason. It also explains the
occasional Wait() failure:
2307.448:trace:alsa:alsa_write_data pad: 480
render.c:2104: Test failed: Wait iteration 3233 gave 102
2307.518:warn:alsa:alsa_write_best_effort writei failed,
  recovering: -32 (Broken pipe)
ALSA lib pcm.c:7316:(snd_pcm_recover) underrun occurred
2307.518:trace:alsa:alsa_write_data pad: 432

- A few alsa_write_best_effort writei failed
However, unlike bug #30118, much to my surprise, the device keeps running.  So
another underrun is signaled a little later, this time causing a lead-in to be
written.  Then audio restarts for another 5 seconds.
2406.776:trace:alsa:alsa_write_data pad: 48
2406.776:warn:alsa:alsa_write_best_effort writei failed, recovering: -32
(Broken pipe)
ALSA lib pcm.c:7316:(snd_pcm_recover) underrun occurred
2406.778:trace:alsa:AudioClient_GetCurrentPadding (0x12b0a8)->(0x32fbe8)
[...]
2406.796:trace:alsa:alsa_write_data pad: 48
[...]
2406.800:trace:alsa:AudioRenderClient_ReleaseBuffer (0x12b0a8)->(480, 0)
2406.806:trace:alsa:alsa_write_data XRun state avail 18000, recovering
2406.807:trace:alsa:alsa_write_data lead-in 6192

I don't know how to explain the difference in behaviour.  Maybe it's solely a
bad interaction with DSound, after all.  Please try out Andrew Eikum's patches
attached to bug #30118.

- The occasional GetBuffer(NULL) test failure is somewhat caused by a
limitation of the winealsa driver.  We need another design to mimic native's
regular decrease of padding when facing huge ALSA periods like 125ms.  Here
mmdevapi's buffer is full, ALSA is over 2/3 full, so mmdevapi will not write
more frames.

Does VLC use DSound for output? Would it use mmdevapi directly if you switched
winecfg to w7 mode?

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