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audio/paaudio: prolong and make latency configurable

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The latency of a connection to the PulseAudio server is determined by
the tlength parameter. This was hardcoded to 10ms, which is a bit too
tight on my machine, causing audio on host and guest to malfunction.
A setting of 15ms works fine here. To allow tweaking, I also made the
setting configurable via the new -audiodev config. This allows to squeeze out better timings in scenarios where the emulation allows it.

I also removed setting of the minreq parameter to (seemingly arbitrary) half the latency, since it showed worse audio quality during my tests. Allowing PulseAudio to request smaller chunks helped.

Signed-off-by: Martin Schrodt <martin@schrodt.org>
Message-id: 20190315084653.120020-3-martin@schrodt.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Martin Schrodt 2019-03-15 09:46:52 +01:00 committed by Gerd Hoffmann
parent baea032ec7
commit f614277765
2 changed files with 11 additions and 7 deletions
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12
audio/paaudio.c
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@ -549,12 +549,8 @@ static int qpa_init_out(HWVoiceOut *hw, struct audsettings *as,
ss.channels = as->nchannels;
ss.rate = as->freq;
/*
* qemu audio tick runs at 100 Hz (by default), so processing
* data chunks worth 10 ms of sound should be a good fit.
*/
ba.tlength = pa_usec_to_bytes (10 * 1000, &ss);
ba.minreq = pa_usec_to_bytes (5 * 1000, &ss);
ba.tlength = pa_usec_to_bytes(ppdo->latency, &ss);
ba.minreq = -1;
ba.maxlength = -1;
ba.prebuf = -1;
@ -818,6 +814,10 @@ static int qpa_validate_per_direction_opts(Audiodev *dev,
pdo->has_buffer_length = true;
pdo->buffer_length = 46440;
}
if (!pdo->has_latency) {
pdo->has_latency = true;
pdo->latency = 15000;
}
return 1;
}

6
qapi/audio.json
View file

@ -206,12 +206,16 @@
#
# @name: name of the sink/source to use
#
# @latency: latency you want PulseAudio to achieve in microseconds
# (default 15000)
#
# Since: 4.0
##
{ 'struct': 'AudiodevPaPerDirectionOptions',
'base': 'AudiodevPerDirectionOptions',
'data': {
'*name': 'str' } }
'*name': 'str',
'*latency': 'uint32' } }
##
# @AudiodevPaOptions: