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paaudio: try to drain the recording stream

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There is no guarantee a single call to pa_stream_peek every
timer_period microseconds can read a recording stream faster
than the data gets produced at the source. Let qpa_read try to
drain the recording stream.

To reproduce the problem:

Start qemu with -audiodev pa,id=audio0,in.mixing-engine=off

On the host connect the qemu recording stream to the monitor of
a hardware output device. While the problem can also be seen
with a hardware input device, it's obvious with the monitor of
a hardware output device.

In the guest start audio recording with audacity and notice the
slow recording data rate.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20200104091122.13971-4-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Volker Rümelin 2020-01-04 10:11:21 +01:00 committed by Gerd Hoffmann
parent 4db3e634c7
commit acc3b63e1b
1 changed files with 25 additions and 16 deletions
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41
audio/paaudio.c
View file

@ -156,34 +156,43 @@ static size_t qpa_read(HWVoiceIn *hw, void *data, size_t length)
{
PAVoiceIn *p = (PAVoiceIn *) hw;
PAConnection *c = p->g->conn;
size_t l;
int r;
size_t total = 0;
pa_threaded_mainloop_lock(c->mainloop);
CHECK_DEAD_GOTO(c, p->stream, unlock_and_fail,
"pa_threaded_mainloop_lock failed\n");
if (!p->read_length) {
r = pa_stream_peek(p->stream, &p->read_data, &p->read_length);
CHECK_SUCCESS_GOTO(c, r == 0, unlock_and_fail,
"pa_stream_peek failed\n");
}
while (total < length) {
size_t l;
int r;
l = MIN(p->read_length, length);
memcpy(data, p->read_data, l);
if (!p->read_length) {
r = pa_stream_peek(p->stream, &p->read_data, &p->read_length);
CHECK_SUCCESS_GOTO(c, r == 0, unlock_and_fail,
"pa_stream_peek failed\n");
if (!p->read_length) {
/* buffer is empty */
break;
}
}
p->read_data += l;
p->read_length -= l;
l = MIN(p->read_length, length - total);
memcpy((char *)data + total, p->read_data, l);
if (!p->read_length) {
r = pa_stream_drop(p->stream);
CHECK_SUCCESS_GOTO(c, r == 0, unlock_and_fail,
"pa_stream_drop failed\n");
p->read_data += l;
p->read_length -= l;
total += l;
if (!p->read_length) {
r = pa_stream_drop(p->stream);
CHECK_SUCCESS_GOTO(c, r == 0, unlock_and_fail,
"pa_stream_drop failed\n");
}
}
pa_threaded_mainloop_unlock(c->mainloop);
return l;
return total;
unlock_and_fail:
pa_threaded_mainloop_unlock(c->mainloop);