AudioTrack: When paused, return cached playback position

An offload output can be re-used between two audio tracks having
the same configuration. A timestamp query for a paused track
while the other is running would return an incorrect time.
To fix this, cache the playback position on a pause() and return
this time when requested until the track is resumed.

Bug: 12826612.
Change-Id: Ia42b8b8fd2ba8993dfcc9abca72da48d71d78d74

1 files changed, 22 insertions, 3 deletions

diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index 11b0b89..e0e1a73 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -85,7 +85,8 @@ AudioTrack::AudioTrack()
     : mStatus(NO_INIT),
       mIsTimed(false),
       mPreviousPriority(ANDROID_PRIORITY_NORMAL),
-      mPreviousSchedulingGroup(SP_DEFAULT)
+      mPreviousSchedulingGroup(SP_DEFAULT),
+      mPausedPosition(0)
 {
 }
 
@@ -106,7 +107,8 @@ AudioTrack::AudioTrack(
     : mStatus(NO_INIT),
       mIsTimed(false),
       mPreviousPriority(ANDROID_PRIORITY_NORMAL),
-      mPreviousSchedulingGroup(SP_DEFAULT)
+      mPreviousSchedulingGroup(SP_DEFAULT),
+      mPausedPosition(0)
 {
     mStatus = set(streamType, sampleRate, format, channelMask,
             frameCount, flags, cbf, user, notificationFrames,
@@ -131,7 +133,8 @@ AudioTrack::AudioTrack(
     : mStatus(NO_INIT),
       mIsTimed(false),
       mPreviousPriority(ANDROID_PRIORITY_NORMAL),
-      mPreviousSchedulingGroup(SP_DEFAULT)
+      mPreviousSchedulingGroup(SP_DEFAULT),
+      mPausedPosition(0)
 {
     mStatus = set(streamType, sampleRate, format, channelMask,
             0 /*frameCount*/, flags, cbf, user, notificationFrames,
@@ -529,6 +532,16 @@ void AudioTrack::pause()
     }
     mProxy->interrupt();
     mAudioTrack->pause();
+
+    if (isOffloaded()) {
+        if (mOutput != 0) {
+            uint32_t halFrames;
+            // OffloadThread sends HAL pause in its threadLoop.. time saved
+            // here can be slightly off
+            AudioSystem::getRenderPosition(mOutput, &halFrames, &mPausedPosition);
+            ALOGV("AudioTrack::pause for offload, cache current position %u", mPausedPosition);
+        }
+    }
 }
 
 status_t AudioTrack::setVolume(float left, float right)
@@ -747,6 +760,12 @@ status_t AudioTrack::getPosition(uint32_t *position) const
     if (isOffloaded()) {
         uint32_t dspFrames = 0;
 
+        if ((mState == STATE_PAUSED) || (mState == STATE_PAUSED_STOPPING)) {
+            ALOGV("getPosition called in paused state, return cached position %u", mPausedPosition);
+            *position = mPausedPosition;
+            return NO_ERROR;
+        }
+
         if (mOutput != 0) {
             uint32_t halFrames;
             AudioSystem::getRenderPosition(mOutput, &halFrames, &dspFrames);