AudioFlinger: refine mixer sleep time logic
When an AudioTrack is in underrun state, the AudioFlinger mixer will
sleep for a short period of time to give the app a chance to fill the
AudioTrack buffer. If the AudioTrack is still not ready during next mixing round,
the mixer will proceed with other tracks.
If an application keeps a steady underrun condition, the AudioFlinger mixer will
alternate between ready and not ready states. In the longer term this will cause the
audio HAL to underrun.
There is a mechanism to reduce the sleep period if the mixer is not ready several times in a
row but this mechanism is defeated by the alternating ready/not ready conditions.
The fix consists in only increasing sleep time if the mixer is ready for at least two
consecutive times.
Issue 5904527.
Change-Id: Id0139bca9be8c4e425ec6d428515c4d8f718e8c9
diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 133dabd..ce701ca 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -1973,11 +1973,14 @@
if (LIKELY(mixerStatus == MIXER_TRACKS_READY)) {
// mix buffers...
mAudioMixer->process();
- sleepTime = 0;
- // increase sleep time progressively when application underrun condition clears
- if (sleepTimeShift > 0) {
+ // increase sleep time progressively when application underrun condition clears.
+ // Only increase sleep time if the mixer is ready for two consecutive times to avoid
+ // that a steady state of alternating ready/not ready conditions keeps the sleep time
+ // such that we would underrun the audio HAL.
+ if ((sleepTime == 0) && (sleepTimeShift > 0)) {
sleepTimeShift--;
}
+ sleepTime = 0;
standbyTime = systemTime() + kStandbyTimeInNsecs;
//TODO: delay standby when effects have a tail
} else {