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paaudio: avoid to clip samples multiple times

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The pulseaudio backend currently converts, clips and copies audio
playback samples in the mixing-engine sample buffer multiple
times.

In qpa_get_buffer_out() the function pa_stream_begin_write()
returns a rather large buffer and this allows audio_pcm_hw_run_out()
in audio/audio.c to copy all samples in the mixing-engine buffer
to the pulse audio buffer. Immediately after copying, qpa_write()
notices with a call to pa_stream_writable_size() that pulse audio
only needs a smaller part of the copied samples and ignores the
rest. This copy and ignore process happens several times for each
audio sample.

To fix this behaviour, call pa_stream_writable_size() in
qpa_get_buffer_out() to limit the number of samples
audio_pcm_hw_run_out() will convert. With this change the
pulseaudio pcm_ops functions put_buffer_out and write are no
longer identical and a separate qpa_put_buffer_out is needed.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 9315afe5-5958-c0b4-ea1e-14769511a9d5@t-online.de
Message-Id: <20210110100239.27588-13-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Volker Rümelin 2021-01-10 11:02:29 +01:00 committed by Gerd Hoffmann
parent 6fb0cd5054
commit bea29e9f2e
1 changed files with 31 additions and 1 deletions
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32
audio/paaudio.c
View file

@ -207,6 +207,7 @@ static void *qpa_get_buffer_out(HWVoiceOut *hw, size_t *size)
PAVoiceOut *p = (PAVoiceOut *) hw;
PAConnection *c = p->g->conn;
void *ret;
size_t l;
int r;
pa_threaded_mainloop_lock(c->mainloop);
@ -214,12 +215,19 @@ static void *qpa_get_buffer_out(HWVoiceOut *hw, size_t *size)
CHECK_DEAD_GOTO(c, p->stream, unlock_and_fail,
"pa_threaded_mainloop_lock failed\n");
l = pa_stream_writable_size(p->stream);
CHECK_SUCCESS_GOTO(c, l != (size_t) -1, unlock_and_fail,
"pa_stream_writable_size failed\n");
*size = -1;
r = pa_stream_begin_write(p->stream, &ret, size);
CHECK_SUCCESS_GOTO(c, r >= 0, unlock_and_fail,
"pa_stream_begin_write failed\n");
pa_threaded_mainloop_unlock(c->mainloop);
if (*size > l) {
*size = l;
}
return ret;
unlock_and_fail:
@ -228,6 +236,28 @@ unlock_and_fail:
return NULL;
}
static size_t qpa_put_buffer_out(HWVoiceOut *hw, void *data, size_t length)
{
PAVoiceOut *p = (PAVoiceOut *)hw;
PAConnection *c = p->g->conn;
int r;
pa_threaded_mainloop_lock(c->mainloop);
CHECK_DEAD_GOTO(c, p->stream, unlock_and_fail,
"pa_threaded_mainloop_lock failed\n");
r = pa_stream_write(p->stream, data, length, NULL, 0LL, PA_SEEK_RELATIVE);
CHECK_SUCCESS_GOTO(c, r >= 0, unlock_and_fail, "pa_stream_write failed\n");
pa_threaded_mainloop_unlock(c->mainloop);
return length;
unlock_and_fail:
pa_threaded_mainloop_unlock(c->mainloop);
return 0;
}
static size_t qpa_write(HWVoiceOut *hw, void *data, size_t length)
{
PAVoiceOut *p = (PAVoiceOut *) hw;
@ -861,7 +891,7 @@ static struct audio_pcm_ops qpa_pcm_ops = {
.fini_out = qpa_fini_out,
.write = qpa_write,
.get_buffer_out = qpa_get_buffer_out,
.put_buffer_out = qpa_write, /* pa handles it */
.put_buffer_out = qpa_put_buffer_out,
.volume_out = qpa_volume_out,
.init_in = qpa_init_in,