Reduce video frame drop rate
The video playback engine depends on having relatively precise audio
progress updates for its A/V sync and frame drop calculations. For small
audio HAL buffer sizes, this was not a problem, but when the HAL buffer
size was > 12 ms, the normal mix buffer size became > 24 ms and this
then caused video problems. The new formula tries to keep the normal
mix buffer size within a closer tolerance of 20 ms to 24 ms.
Also use consistent term: multiplier instead of multiple.
Bug: 6479613
Change-Id: I903bad74461908e8c8f0a61e99ab5e24d5c44433
diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 51a8367..e1fae82 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -142,6 +142,8 @@
// minimum normal mix buffer size, expressed in milliseconds rather than frames
static const uint32_t kMinNormalMixBufferSizeMs = 20;
+// maximum normal mix buffer size
+static const uint32_t kMaxNormalMixBufferSizeMs = 24;
nsecs_t AudioFlinger::mStandbyTimeInNsecs = kDefaultStandbyTimeInNsecs;
@@ -151,9 +153,9 @@
FastMixer_Always, // always initialize and use, even if not needed: for debugging only
// normal mixer multiplier is 1
FastMixer_Static, // initialize if needed, then use all the time if initialized,
- // multipler is calculated based on minimum normal mixer buffer size
+ // multiplier is calculated based on min & max normal mixer buffer size
FastMixer_Dynamic, // initialize if needed, then use dynamically depending on track load,
- // multipler is calculated based on minimum normal mixer buffer size
+ // multiplier is calculated based on min & max normal mixer buffer size
// FIXME for FastMixer_Dynamic:
// Supporting this option will require fixing HALs that can't handle large writes.
// For example, one HAL implementation returns an error from a large write,
@@ -1950,18 +1952,42 @@
}
// Calculate size of normal mix buffer relative to the HAL output buffer size
- uint32_t multiple = 1;
+ double multiplier = 1.0;
if (mType == MIXER && (kUseFastMixer == FastMixer_Static || kUseFastMixer == FastMixer_Dynamic)) {
size_t minNormalFrameCount = (kMinNormalMixBufferSizeMs * mSampleRate) / 1000;
- multiple = (minNormalFrameCount + mFrameCount - 1) / mFrameCount;
- // force multiple to be even, for compatibility with doubling of fast tracks due to HAL SRC
- // (it would be unusual for the normal mix buffer size to not be a multiple of fast track)
- // FIXME this rounding up should not be done if no HAL SRC
- if ((multiple > 2) && (multiple & 1)) {
- ++multiple;
+ size_t maxNormalFrameCount = (kMaxNormalMixBufferSizeMs * mSampleRate) / 1000;
+ // round up minimum and round down maximum to nearest 16 frames to satisfy AudioMixer
+ minNormalFrameCount = (minNormalFrameCount + 15) & ~15;
+ maxNormalFrameCount = maxNormalFrameCount & ~15;
+ if (maxNormalFrameCount < minNormalFrameCount) {
+ maxNormalFrameCount = minNormalFrameCount;
+ }
+ multiplier = (double) minNormalFrameCount / (double) mFrameCount;
+ if (multiplier <= 1.0) {
+ multiplier = 1.0;
+ } else if (multiplier <= 2.0) {
+ if (2 * mFrameCount <= maxNormalFrameCount) {
+ multiplier = 2.0;
+ } else {
+ multiplier = (double) maxNormalFrameCount / (double) mFrameCount;
+ }
+ } else {
+ // prefer an even multiplier, for compatibility with doubling of fast tracks due to HAL SRC
+ // (it would be unusual for the normal mix buffer size to not be a multiple of fast
+ // track, but we sometimes have to do this to satisfy the maximum frame count constraint)
+ // FIXME this rounding up should not be done if no HAL SRC
+ uint32_t truncMult = (uint32_t) multiplier;
+ if ((truncMult & 1)) {
+ if ((truncMult + 1) * mFrameCount <= maxNormalFrameCount) {
+ ++truncMult;
+ }
+ }
+ multiplier = (double) truncMult;
}
}
- mNormalFrameCount = multiple * mFrameCount;
+ mNormalFrameCount = multiplier * mFrameCount;
+ // round up to nearest 16 frames to satisfy AudioMixer
+ mNormalFrameCount = (mNormalFrameCount + 15) & ~15;
ALOGI("HAL output buffer size %u frames, normal mix buffer size %u frames", mFrameCount, mNormalFrameCount);
// FIXME - Current mixer implementation only supports stereo output: Always