diff --git a/include/private/media/AudioTrackShared.h b/include/private/media/AudioTrackShared.h
index 395f164..7fd9379 100644
--- a/include/private/media/AudioTrackShared.h
+++ b/include/private/media/AudioTrackShared.h
@@ -360,6 +360,7 @@
     //      which must be > 0.
     //  buffer->mNonContig is unused.
     //  buffer->mRaw is unused.
+    //  ackFlush is true iff being called from Track::start to acknowledge a pending flush.
     // On exit:
     //  buffer->mFrameCount has the actual number of contiguous available frames,
     //      which is always 0 when the return status != NO_ERROR.
@@ -370,7 +371,7 @@
     //  NO_ERROR    Success, buffer->mFrameCount > 0.
     //  WOULD_BLOCK No frames are available.
     //  NO_INIT     Shared memory is corrupt.
-    virtual status_t    obtainBuffer(Buffer* buffer);
+    virtual status_t    obtainBuffer(Buffer* buffer, bool ackFlush = false);
 
     // Release (some of) the frames last obtained.
     // On entry, buffer->mFrameCount should have the number of frames to release,
@@ -437,7 +438,7 @@
 public:
     virtual size_t      framesReady();
     virtual void        framesReadyIsCalledByMultipleThreads();
-    virtual status_t    obtainBuffer(Buffer* buffer);
+    virtual status_t    obtainBuffer(Buffer* buffer, bool ackFlush);
     virtual void        releaseBuffer(Buffer* buffer);
     virtual void        tallyUnderrunFrames(uint32_t frameCount);
     virtual uint32_t    getUnderrunFrames() const { return 0; }
diff --git a/media/libmedia/AudioTrackShared.cpp b/media/libmedia/AudioTrackShared.cpp
index da73d65..caa7900 100644
--- a/media/libmedia/AudioTrackShared.cpp
+++ b/media/libmedia/AudioTrackShared.cpp
@@ -506,7 +506,7 @@
 {
 }
 
-status_t ServerProxy::obtainBuffer(Buffer* buffer)
+status_t ServerProxy::obtainBuffer(Buffer* buffer, bool ackFlush)
 {
     LOG_ALWAYS_FATAL_IF(buffer == NULL || buffer->mFrameCount == 0);
     if (mIsShutdown) {
@@ -579,7 +579,11 @@
     buffer->mRaw = part1 > 0 ?
             &((char *) mBuffers)[(mIsOut ? front : rear) * mFrameSize] : NULL;
     buffer->mNonContig = availToServer - part1;
-    mUnreleased = part1;
+    // After flush(), allow releaseBuffer() on a previously obtained buffer;
+    // see "Acknowledge any pending flush()" in audioflinger/Tracks.cpp.
+    if (!ackFlush) {
+        mUnreleased = part1;
+    }
     return part1 > 0 ? NO_ERROR : WOULD_BLOCK;
     }
 no_init:
@@ -761,7 +765,7 @@
     return (ssize_t) position;
 }
 
-status_t StaticAudioTrackServerProxy::obtainBuffer(Buffer* buffer)
+status_t StaticAudioTrackServerProxy::obtainBuffer(Buffer* buffer, bool ackFlush)
 {
     if (mIsShutdown) {
         buffer->mFrameCount = 0;
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 47dcca6..9c8fd1f 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -3884,15 +3884,11 @@
     :   DirectOutputThread(audioFlinger, output, id, device, OFFLOAD),
         mHwPaused(false),
         mFlushPending(false),
-        mPausedBytesRemaining(0)
+        mPausedBytesRemaining(0),
+        mPreviousTrack(NULL)
 {
 }
 
-AudioFlinger::OffloadThread::~OffloadThread()
-{
-    mPreviousTrack.clear();
-}
-
 void AudioFlinger::OffloadThread::threadLoop_exit()
 {
     if (mFlushPending || mHwPaused) {
@@ -3928,7 +3924,7 @@
         Track* const track = t.get();
         audio_track_cblk_t* cblk = track->cblk();
         if (mPreviousTrack != NULL) {
-            if (t != mPreviousTrack) {
+            if (t.get() != mPreviousTrack) {
                 // Flush any data still being written from last track
                 mBytesRemaining = 0;
                 if (mPausedBytesRemaining) {
@@ -3943,7 +3939,7 @@
                 }
             }
         }
-        mPreviousTrack = t;
+        mPreviousTrack = t.get();
         bool last = (i == (count - 1));
         if (track->isPausing()) {
             track->setPaused();
@@ -4008,7 +4004,8 @@
                     // has been written
                     ALOGV("OffloadThread: underrun and STOPPING_1 -> draining, STOPPING_2");
                     track->mState = TrackBase::STOPPING_2; // so presentation completes after drain
-                    if (last) {
+                    // do not drain if no data was ever sent to HAL (mStandby == true)
+                    if (last && !mStandby) {
                         sleepTime = 0;
                         standbyTime = systemTime() + standbyDelay;
                         mixerStatus = MIXER_DRAIN_TRACK;
@@ -4022,8 +4019,8 @@
                     }
                 }
             } else if (track->isStopping_2()) {
-                // Drain has completed, signal presentation complete
-                if (!(mDrainSequence & 1) || !last) {
+                // Drain has completed or we are in standby, signal presentation complete
+                if (!(mDrainSequence & 1) || !last || mStandby) {
                     track->mState = TrackBase::STOPPED;
                     size_t audioHALFrames =
                             (mOutput->stream->get_latency(mOutput->stream)*mSampleRate) / 1000;
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index 802b784..a5d2169 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -735,7 +735,7 @@
 
     OffloadThread(const sp<AudioFlinger>& audioFlinger, AudioStreamOut* output,
                         audio_io_handle_t id, uint32_t device);
-    virtual                 ~OffloadThread();
+    virtual                 ~OffloadThread() {};
 
 protected:
     // threadLoop snippets
@@ -755,7 +755,7 @@
     bool        mFlushPending;
     size_t      mPausedWriteLength;     // length in bytes of write interrupted by pause
     size_t      mPausedBytesRemaining;  // bytes still waiting in mixbuffer after resume
-    sp<Track>   mPreviousTrack;         // used to detect track switch
+    Track       *mPreviousTrack;         // used to detect track switch
 };
 
 class AsyncCallbackThread : public Thread {
diff --git a/services/audioflinger/Tracks.cpp b/services/audioflinger/Tracks.cpp
index e93833f..363bc9d 100644
--- a/services/audioflinger/Tracks.cpp
+++ b/services/audioflinger/Tracks.cpp
@@ -608,7 +608,7 @@
             // and for fast tracks the track is not yet in the fast mixer thread's active set.
             ServerProxy::Buffer buffer;
             buffer.mFrameCount = 1;
-            (void) mAudioTrackServerProxy->obtainBuffer(&buffer);
+            (void) mAudioTrackServerProxy->obtainBuffer(&buffer, true /*ackFlush*/);
         }
     } else {
         status = BAD_VALUE;