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authorVolker RĂ¼melin <vr_qemu@t-online.de>2020-09-20 19:17:22 +0200
committerGerd Hoffmann <kraxel@redhat.com>2020-09-23 08:19:42 +0200
commit4c3356f96557e848f0323772f9502d60817682dc (patch)
tree90ecf10ad23a3203aef9dd929fa07ec59b6ab1e7
parentd4b70fa4ede25734d2ff76503c735e6fcee6cfda (diff)
downloadfocaccia-qemu-4c3356f96557e848f0323772f9502d60817682dc.tar.gz
focaccia-qemu-4c3356f96557e848f0323772f9502d60817682dc.zip
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 RĂ¼melin <vr_qemu@t-online.de>
Message-id: 20200920171729.15861-2-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Diffstat (limited to '')
-rw-r--r--audio/audio.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/audio/audio.c b/audio/audio.c
index 1a68cfaafb..7b660dd0c4 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -1091,12 +1091,15 @@ static size_t audio_pcm_hw_run_out(HWVoiceOut *hw, size_t live)
     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;