audio/audio: fix video playback slowdown with spiceaudio
This patch allows the audio backends get_buffer_out() functions
to drop audio data and mitigates a bug reported on the qemu-devel
mailing list.
https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg03832.html
The new rules for the variables buf and size returned by
get_buffer_out() are:
size == 0: Downstream playback buffer is full. Retry later.
size > 0, buf != NULL: Copy size bytes to buf for playback.
size > 0, buf == NULL: Drop size bytes.
The audio playback rate with spiceaudio for the no audio case is
too fast, but that's what we had before commit fb35c2cec5
"audio/dsound: fix invalid parameters error". The complete fix
comes with the next patch.
Reported-by: Qi Zhou <atmgnd@outlook.com>
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20200920171729.15861-2-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/audio/audio.c b/audio/audio.c
index 1a68cfa..7b660dd 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -1091,12 +1091,15 @@
while (live) {
size_t size, decr, proc;
void *buf = hw->pcm_ops->get_buffer_out(hw, &size);
- if (!buf || size == 0) {
+
+ if (size == 0) {
break;
}
decr = MIN(size / hw->info.bytes_per_frame, live);
- audio_pcm_hw_clip_out(hw, buf, decr);
+ if (buf) {
+ audio_pcm_hw_clip_out(hw, buf, decr);
+ }
proc = hw->pcm_ops->put_buffer_out(hw, buf,
decr * hw->info.bytes_per_frame) /
hw->info.bytes_per_frame;
