Commit 0609231f authored Jan 23, 2012 by Eric Laurent

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

parent 0b089655

services/audioflinger/AudioFlinger.cpp

+6 −3

Original line number	Diff line number	Diff line
		@@ -1973,11 +1973,14 @@ bool AudioFlinger::MixerThread::threadLoop()
		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 {