Track volume cleanup
Always read and write track volumes atomically. In most places this was
already being done, but there were a couple places where the left and
right channels were read independently.
Changed constant MAX_GAIN_INT to be a uint32_t instead of a float.
It is always used as a uint32_t in comparisons and assignments.
Use MAX_GAIN_INT in more places.
Now that volume is always accessed atomically, removed the union
and alias for uint16_t volume[2], and kept only volumeLR.
Removed volatile as it's meaningless.
In AudioFlinger, clamp the track volumes read from shared memory
before applying master and stream volume.
Change-Id: If65e2b27e5bc3db5bf75540479843041b58433f0
diff --git a/include/private/media/AudioTrackShared.h b/include/private/media/AudioTrackShared.h
index 33a92cd..ffc546e 100644
--- a/include/private/media/AudioTrackShared.h
+++ b/include/private/media/AudioTrackShared.h
@@ -71,10 +71,13 @@
uint32_t loopStart;
uint32_t loopEnd;
int loopCount;
- volatile union {
- uint16_t volume[2];
- uint32_t volumeLR;
- };
+
+ // Channel volumes are fixed point U4.12, so 0x1000 means 1.0.
+ // Left channel is in [0:15], right channel is in [16:31].
+ // Always read and write the combined pair atomically.
+ // For AudioTrack only, not used by AudioRecord.
+ uint32_t volumeLR;
+
uint32_t sampleRate;
// NOTE: audio_track_cblk_t::frameSize is not equal to AudioTrack::frameSize() for
// 8 bit PCM data: in this case, mCblk->frameSize is based on a sample size of