paaudio: send recorded data in smaller chunks

Tell PulseAudio to send recorded audio data in smaller chunks
than timer_period, so there's a good chance that qemu can read
recorded audio data every time it looks for new data.

PulseAudio tries to send buffer updates at a fragsize / 2 rate.
With fragsize = timer_period / 2 * 3 the update rate is 75% of
timer_period. The lower limit for the recording buffer size
maxlength is fragsize * 2.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 9315afe5-5958-c0b4-ea1e-14769511a9d5@t-online.de
Message-Id: <20210110100239.27588-19-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

audio/paaudio.c

@@ -568,8 +568,9 @@ static int qpa_init_in(HWVoiceIn *hw, struct audsettings *as, void *drv_opaque)
     ss.channels = as->nchannels;
     ss.rate = as->freq;
 
-    ba.fragsize = pa_usec_to_bytes(ppdo->latency, &ss);
-    ba.maxlength = pa_usec_to_bytes(ppdo->latency * 2, &ss);
+    ba.fragsize = pa_usec_to_bytes((g->dev->timer_period >> 1) * 3, &ss);
+    ba.maxlength = pa_usec_to_bytes(
+        MAX(ppdo->latency, g->dev->timer_period * 3), &ss);
     ba.minreq = -1;
     ba.prebuf = -1;