Commit f6142777 authored by Martin Schrodt's avatar Martin Schrodt Committed by Gerd Hoffmann
Browse files

audio/paaudio: prolong and make latency configurable 



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: default avatarMartin Schrodt <martin@schrodt.org>
Message-id: 20190315084653.120020-3-martin@schrodt.org
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent baea032e

audio/paaudio.c

+6 −6
Original line number Diff line number Diff line
@@ -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;

}

qapi/audio.json

+5 −1
Original line number Diff line number Diff line
@@ -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: