diff --git a/api/current.xml b/api/current.xml
index 2d13363..c8384e4 100644
--- a/api/current.xml
+++ b/api/current.xml
@@ -78336,6 +78336,19 @@
 <method name="startTone"
  return="boolean"
  abstract="false"
+ native="false"
+ synchronized="false"
+ static="false"
+ final="false"
+ deprecated="not deprecated"
+ visibility="public"
+>
+<parameter name="toneType" type="int">
+</parameter>
+</method>
+<method name="startTone"
+ return="boolean"
+ abstract="false"
  native="true"
  synchronized="false"
  static="false"
@@ -78345,6 +78358,8 @@
 >
 <parameter name="toneType" type="int">
 </parameter>
+<parameter name="durationMs" type="int">
+</parameter>
 </method>
 <method name="stopTone"
  return="void"
diff --git a/core/jni/android_media_ToneGenerator.cpp b/core/jni/android_media_ToneGenerator.cpp
index a4388de..07bb1ab 100644
--- a/core/jni/android_media_ToneGenerator.cpp
+++ b/core/jni/android_media_ToneGenerator.cpp
@@ -38,7 +38,7 @@
 };
 static fields_t fields;
 
-static jboolean android_media_ToneGenerator_startTone(JNIEnv *env, jobject thiz, jint toneType) {
+static jboolean android_media_ToneGenerator_startTone(JNIEnv *env, jobject thiz, jint toneType, jint durationMs) {
     LOGV("android_media_ToneGenerator_startTone: %x\n", (int)thiz);
 
     ToneGenerator *lpToneGen = (ToneGenerator *)env->GetIntField(thiz,
@@ -48,7 +48,7 @@
         return false;
     }
 
-    return lpToneGen->startTone(toneType);
+    return lpToneGen->startTone(toneType, durationMs);
 }
 
 static void android_media_ToneGenerator_stopTone(JNIEnv *env, jobject thiz) {
@@ -120,7 +120,7 @@
 // ----------------------------------------------------------------------------
 
 static JNINativeMethod gMethods[] = {
-    { "startTone", "(I)Z", (void *)android_media_ToneGenerator_startTone },
+    { "startTone", "(II)Z", (void *)android_media_ToneGenerator_startTone },
     { "stopTone", "()V", (void *)android_media_ToneGenerator_stopTone },
     { "release", "()V", (void *)android_media_ToneGenerator_release },
     { "native_setup", "(II)V", (void *)android_media_ToneGenerator_native_setup },
diff --git a/include/media/ToneGenerator.h b/include/media/ToneGenerator.h
index eafa661..ea6bf5d 100644
--- a/include/media/ToneGenerator.h
+++ b/include/media/ToneGenerator.h
@@ -154,7 +154,7 @@
     ToneGenerator(int streamType, float volume);
     ~ToneGenerator();
 
-    bool startTone(int toneType);
+    bool startTone(int toneType, int durationMs = -1);
     void stopTone();
 
     bool isInited() { return (mState == TONE_IDLE)?false:true;}
@@ -246,6 +246,7 @@
     // NOTE: because mTotalSmp, mNextSegSmp are stored on 32 bit, current design will operate properly
     // only if tone duration is less than about 27 Hours(@44100Hz sampling rate). If this time is exceeded,
     // no crash will occur but tone sequence will show a glitch.
+    unsigned int mMaxSmp;  // Maximum number of audio samples played (maximun tone duration)
 
     unsigned short mCurSegment;  // Current segment index in ToneDescriptor segments[]
     unsigned short mCurCount;  // Current sequence repeat count
diff --git a/libs/audioflinger/AudioFlinger.cpp b/libs/audioflinger/AudioFlinger.cpp
index 8cb89c3..e2b6b51 100644
--- a/libs/audioflinger/AudioFlinger.cpp
+++ b/libs/audioflinger/AudioFlinger.cpp
@@ -1160,7 +1160,7 @@
 
 bool AudioFlinger::MixerThread::threadLoop()
 {
-    unsigned long sleepTime = kBufferRecoveryInUsecs;
+    unsigned long sleepTime = 0;
     int16_t* curBuf = mMixBuffer;
     Vector< sp<Track> > tracksToRemove;
     size_t enabledTracks = 0;
@@ -1215,6 +1215,7 @@
                     }
 
                     standbyTime = systemTime() + kStandbyTimeInNsecs;
+                    sleepTime = 0;
                     continue;
                 }
             }
@@ -1222,14 +1223,31 @@
             enabledTracks = prepareTracks_l(activeTracks, &tracksToRemove);
        }
 
-        if (LIKELY(enabledTracks)) {
-            // mix buffers...
-            mAudioMixer->process(curBuf);
 
-            // output audio to hardware
-            if (mSuspended) {
-                usleep(kMaxBufferRecoveryInUsecs);
+        // output audio to hardware
+        if (mSuspended) {
+            usleep(kMaxBufferRecoveryInUsecs);
+        } else {
+            if (LIKELY(enabledTracks)) {
+                // mix buffers...
+                mAudioMixer->process(curBuf);
+                sleepTime = 0;
+                standbyTime = systemTime() + kStandbyTimeInNsecs;
             } else {
+                sleepTime += kBufferRecoveryInUsecs;
+                // There was nothing to mix this round, which means all
+                // active tracks were late. Sleep a little bit to give
+                // them another chance. If we're too late, write 0s to audio
+                // hardware to avoid underrun.
+                if (sleepTime < kMaxBufferRecoveryInUsecs) {
+                    usleep(kBufferRecoveryInUsecs);
+                } else {
+                    memset (curBuf, 0, mixBufferSize);
+                    sleepTime = 0;
+                }
+            }
+            // sleepTime == 0 means PCM data were written to mMixBuffer[]
+            if (sleepTime == 0) {
                 mLastWriteTime = systemTime();
                 mInWrite = true;
                 int bytesWritten = (int)mOutput->write(curBuf, mixBufferSize);
@@ -1237,24 +1255,11 @@
                 mNumWrites++;
                 mInWrite = false;
                 mStandby = false;
-                nsecs_t temp = systemTime();
-                standbyTime = temp + kStandbyTimeInNsecs;
-                nsecs_t delta = temp - mLastWriteTime;
+                nsecs_t delta = systemTime() - mLastWriteTime;
                 if (delta > maxPeriod) {
                     LOGW("write blocked for %llu msecs", ns2ms(delta));
                     mNumDelayedWrites++;
                 }
-                sleepTime = kBufferRecoveryInUsecs;
-            }
-        } else {
-            // There was nothing to mix this round, which means all
-            // active tracks were late. Sleep a little bit to give
-            // them another chance. If we're too late, the audio
-            // hardware will zero-fill for us.
-            // LOGV("thread %p no buffers - usleep(%lu)", this, sleepTime);
-            usleep(sleepTime);
-            if (sleepTime < kMaxBufferRecoveryInUsecs) {
-                sleepTime += kBufferRecoveryInUsecs;
             }
         }
 
@@ -1568,7 +1573,7 @@
 
 bool AudioFlinger::DirectOutputThread::threadLoop()
 {
-    unsigned long sleepTime = kBufferRecoveryInUsecs;
+    unsigned long sleepTime = 0;
     sp<Track> trackToRemove;
     sp<Track> activeTrack;
     nsecs_t standbyTime = systemTime();
@@ -1618,6 +1623,7 @@
                     }
 
                     standbyTime = systemTime() + kStandbyTimeInNsecs;
+                    sleepTime = 0;
                     continue;
                 }
             }
@@ -1710,46 +1716,48 @@
             }
        }
 
-        if (activeTrack != 0) {
-            AudioBufferProvider::Buffer buffer;
-            size_t frameCount = mFrameCount;
-            curBuf = (int8_t *)mMixBuffer;
-            // output audio to hardware
-            mLastWriteTime = systemTime();
-            mInWrite = true;
-            while(frameCount) {
-                buffer.frameCount = frameCount;
-                activeTrack->getNextBuffer(&buffer);
-                if (UNLIKELY(buffer.raw == 0)) {
-                    memset(curBuf, 0, frameCount * mFrameSize);
-                    break;
+        // output audio to hardware
+        if (mSuspended) {
+            usleep(kMaxBufferRecoveryInUsecs);
+        } else {
+            if (activeTrack != 0) {
+                AudioBufferProvider::Buffer buffer;
+                size_t frameCount = mFrameCount;
+                curBuf = (int8_t *)mMixBuffer;
+                // output audio to hardware
+                while(frameCount) {
+                    buffer.frameCount = frameCount;
+                    activeTrack->getNextBuffer(&buffer);
+                    if (UNLIKELY(buffer.raw == 0)) {
+                        memset(curBuf, 0, frameCount * mFrameSize);
+                        break;
+                    }
+                    memcpy(curBuf, buffer.raw, buffer.frameCount * mFrameSize);
+                    frameCount -= buffer.frameCount;
+                    curBuf += buffer.frameCount * mFrameSize;
+                    activeTrack->releaseBuffer(&buffer);
                 }
-                memcpy(curBuf, buffer.raw, buffer.frameCount * mFrameSize);
-                frameCount -= buffer.frameCount;
-                curBuf += buffer.frameCount * mFrameSize;
-                activeTrack->releaseBuffer(&buffer);
-            }
-            if (mSuspended) {
-                usleep(kMaxBufferRecoveryInUsecs);
+                sleepTime = 0;
+                standbyTime = systemTime() + kStandbyTimeInNsecs;
             } else {
+                sleepTime += kBufferRecoveryInUsecs;
+                if (sleepTime < kMaxBufferRecoveryInUsecs) {
+                    usleep(kBufferRecoveryInUsecs);
+                } else {
+                    memset (mMixBuffer, 0, mFrameCount * mFrameSize);
+                    sleepTime = 0;
+                }
+            }
+
+            // sleepTime == 0 means PCM data were written to mMixBuffer[]
+            if (sleepTime == 0) {
+                mLastWriteTime = systemTime();
+                mInWrite = true;
                 int bytesWritten = (int)mOutput->write(mMixBuffer, mixBufferSize);
                 if (bytesWritten) mBytesWritten += bytesWritten;
                 mNumWrites++;
                 mInWrite = false;
                 mStandby = false;
-                nsecs_t temp = systemTime();
-                standbyTime = temp + kStandbyTimeInNsecs;
-                sleepTime = kBufferRecoveryInUsecs;
-            }
-        } else {
-            // There was nothing to mix this round, which means all
-            // active tracks were late. Sleep a little bit to give
-            // them another chance. If we're too late, the audio
-            // hardware will zero-fill for us.
-            //LOGV("no buffers - usleep(%lu)", sleepTime);
-            usleep(sleepTime);
-            if (sleepTime < kMaxBufferRecoveryInUsecs) {
-                sleepTime += kBufferRecoveryInUsecs;
             }
         }
 
diff --git a/media/java/android/media/ToneGenerator.java b/media/java/android/media/ToneGenerator.java
index c60a1ac..d4ae80f 100644
--- a/media/java/android/media/ToneGenerator.java
+++ b/media/java/android/media/ToneGenerator.java
@@ -744,7 +744,7 @@
      * This method starts the playback of a tone of the specified type.
      * only one tone can play at a time: if a tone is playing while this method is called,
      * this tone is stopped and replaced by the one requested.
-     * @param toneType   The type of tone generate chosen from the following list:
+     * @param toneType   The type of tone generated chosen from the following list:
      * <ul>
      * <li>{@link #TONE_DTMF_0}
      * <li>{@link #TONE_DTMF_1}
@@ -846,7 +846,18 @@
      * </ul>
      * @see #ToneGenerator(int, int)
     */
-    public native boolean startTone(int toneType);
+    public boolean startTone(int toneType) {
+        return startTone(toneType, -1);
+    }
+
+    /**
+     * This method starts the playback of a tone of the specified type for the specified duration.
+     * @param toneType   The type of tone generated @see #startTone(int).
+     * @param durationMs  The tone duration in milliseconds. If the tone is limited in time by definition,
+     * the actual duration will be the minimum of durationMs and the defined tone duration. Setting durationMs to -1,
+     * is equivalent to calling #startTone(int).
+    */
+    public native boolean startTone(int toneType, int durationMs);
 
     /**
      * This method stops the tone currently playing playback.
diff --git a/media/libmedia/ToneGenerator.cpp b/media/libmedia/ToneGenerator.cpp
index 799c349..4008bfd 100644
--- a/media/libmedia/ToneGenerator.cpp
+++ b/media/libmedia/ToneGenerator.cpp
@@ -791,7 +791,6 @@
 //        generators, instantiates output audio track.
 //
 //    Input:
-//        toneType:        Type of tone generated (values in enum tone_type)
 //        streamType:        Type of stream used for tone playback (enum AudioTrack::stream_type)
 //        volume:            volume applied to tone (0.0 to 1.0)
 //
@@ -869,13 +868,16 @@
 //    Description:    Starts tone playback.
 //
 //    Input:
-//        none
+//        toneType:        Type of tone generated (values in enum tone_type)
+//        durationMs:      The tone duration in milliseconds. If the tone is limited in time by definition,
+//              the actual duration will be the minimum of durationMs and the defined tone duration.
+//              Ommiting or setting durationMs to -1 does not limit tone duration.
 //
 //    Output:
 //        none
 //
 ////////////////////////////////////////////////////////////////////////////////
-bool ToneGenerator::startTone(int toneType) {
+bool ToneGenerator::startTone(int toneType, int durationMs) {
     bool lResult = false;
 
     if ((toneType < 0) || (toneType >= NUM_TONES))
@@ -896,6 +898,17 @@
     toneType = getToneForRegion(toneType);
     mpNewToneDesc = &sToneDescriptors[toneType];
 
+    if (durationMs == -1) {
+        mMaxSmp = TONEGEN_INF;
+    } else {
+        if (durationMs > (int)(TONEGEN_INF / mSamplingRate)) {
+            mMaxSmp = (durationMs / 1000) * mSamplingRate;
+        } else {
+            mMaxSmp = (durationMs * mSamplingRate) / 1000;
+        }
+        LOGV("startTone, duration limited to %d ms", durationMs);
+    }
+
     if (mState == TONE_INIT) {
         if (prepareWave()) {
             LOGV("Immediate start, time %d\n", (unsigned int)(systemTime()/1000000));
@@ -1102,11 +1115,17 @@
 
 
         // Exit if tone sequence is over
-        if (lpToneDesc->segments[lpToneGen->mCurSegment].duration == 0) {
+        if (lpToneDesc->segments[lpToneGen->mCurSegment].duration == 0 ||
+            lpToneGen->mTotalSmp > lpToneGen->mMaxSmp) {
             if (lpToneGen->mState == TONE_PLAYING) {
                 lpToneGen->mState = TONE_STOPPING;
             }
-            goto audioCallback_EndLoop;
+            if (lpToneDesc->segments[lpToneGen->mCurSegment].duration == 0) {
+                goto audioCallback_EndLoop;
+            }
+            // fade out before stopping if maximum duraiton reached
+            lWaveCmd = WaveGenerator::WAVEGEN_STOP;
+            lpToneGen->mNextSegSmp = TONEGEN_INF; // forced to skip state machine management below
         }
 
         if (lpToneGen->mTotalSmp > lpToneGen->mNextSegSmp) {