diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 485e320..93b1642 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -757,8 +757,12 @@
     // 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;
 }
@@ -875,8 +879,12 @@
     // 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;
 }
@@ -1894,11 +1902,10 @@
 
         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());
-
                 }
             }
         }
@@ -1927,7 +1934,7 @@
     // 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()) {
         closeOutputFinish(thread);
     }
 
@@ -2375,6 +2382,9 @@
 {
     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;
@@ -2689,7 +2699,7 @@
     // Check whether the destination thread has a channel count of FCC_2, which is
     // currently required for (most) effects. Prevent moving the effect chain here rather
     // than disabling the addEffect_l() call in dstThread below.
-    if ((dstThread->type() == ThreadBase::MIXER || dstThread->type() == ThreadBase::DUPLICATING) &&
+    if ((dstThread->type() == ThreadBase::MIXER || dstThread->isDuplicating()) &&
             dstThread->mChannelCount != FCC_2) {
         ALOGW("moveEffectChain_l() effect chain failed because"
                 " destination thread %p channel count(%u) != %u",
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 2c4d801..f2af312 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -5215,10 +5215,13 @@
             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 0a5597f..37bacae 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -230,6 +230,8 @@
 
                 // 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