diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index acbd19a..0aef53f 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -646,8 +646,12 @@
     // assigned to HALs which do not have master volume support will apply
     // master volume during the mix operation.  Threads with HALs which do
     // support master volume will simply ignore the setting.
-    for (size_t i = 0; i < mPlaybackThreads.size(); i++)
+    for (size_t i = 0; i < mPlaybackThreads.size(); i++) {
+        if (mPlaybackThreads.valueAt(i)->isDuplicating()) {
+            continue;
+        }
         mPlaybackThreads.valueAt(i)->setMasterVolume(value);
+    }
 
     return NO_ERROR;
 }
@@ -753,8 +757,12 @@
     // assigned to HALs which do not have master mute support will apply master
     // mute during the mix operation.  Threads with HALs which do support master
     // mute will simply ignore the setting.
-    for (size_t i = 0; i < mPlaybackThreads.size(); i++)
+    for (size_t i = 0; i < mPlaybackThreads.size(); i++) {
+        if (mPlaybackThreads.valueAt(i)->isDuplicating()) {
+            continue;
+        }
         mPlaybackThreads.valueAt(i)->setMasterMute(muted);
+    }
 
     return NO_ERROR;
 }
@@ -1596,11 +1604,10 @@
 
         if (thread->type() == ThreadBase::MIXER) {
             for (size_t i = 0; i < mPlaybackThreads.size(); i++) {
-                if (mPlaybackThreads.valueAt(i)->type() == ThreadBase::DUPLICATING) {
+                if (mPlaybackThreads.valueAt(i)->isDuplicating()) {
                     DuplicatingThread *dupThread =
                             (DuplicatingThread *)mPlaybackThreads.valueAt(i).get();
                     dupThread->removeOutputTrack((MixerThread *)thread.get());
-
                 }
             }
         }
@@ -1627,7 +1634,7 @@
     // The thread entity (active unit of execution) is no longer running here,
     // but the ThreadBase container still exists.
 
-    if (thread->type() != ThreadBase::DUPLICATING) {
+    if (!thread->isDuplicating()) {
         AudioStreamOut *out = thread->clearOutput();
         ALOG_ASSERT(out != NULL, "out shouldn't be NULL");
         // from now on thread->mOutput is NULL
@@ -2000,6 +2007,9 @@
 {
     for (size_t i = 0; i < mPlaybackThreads.size(); i++) {
         PlaybackThread *thread = mPlaybackThreads.valueAt(i).get();
+        if(thread->isDuplicating()) {
+            continue;
+        }
         AudioStreamOut *output = thread->getOutput();
         if (output != NULL && output->audioHwDev == mPrimaryHardwareDev) {
             return thread;
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 3d657b3..a9eaa8a 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -4306,10 +4306,13 @@
             mOutputTracks[i]->destroy();
             mOutputTracks.removeAt(i);
             updateWaitTime_l();
+            if (thread->getOutput() == mOutput) {
+                mOutput = NULL;
+            }
             return;
         }
     }
-    ALOGV("removeOutputTrack(): unkonwn thread: %p", thread);
+    ALOGV("removeOutputTrack(): unknown thread: %p", thread);
 }
 
 // caller must hold mLock
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index 207f1eb..bb92df1 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -118,6 +118,8 @@
 
                 // static externally-visible
                 type_t      type() const { return mType; }
+                bool isDuplicating() const { return (mType == DUPLICATING); }
+
                 audio_io_handle_t id() const { return mId;}
 
                 // dynamic externally-visible