commit 8ac9f8d1c708dc8bb853f7697f10051031eb73c5
author Eric Laurent <elaurent@google.com> Fri Dec 18 05:47:48 2009 -0800
committer Eric Laurent <elaurent@google.com> Tue Dec 22 09:06:46 2009 -0800
tree fa01ca6b36a08093fa24668723c17ff1189513c1
parent e4c2a37624612c9708d0767f8643a10502e6887a

Fix issue 2323920: Notification & A2DP audio stutter.

Modified AudioFlinger duplicating output thread so that audio tracks are not mixed until both outputs (A2DP and hardware) have exited standby mode. This avoids to have one output far ahead of the other and audio frames dropped because the compensation mechanism cannot keep up.
Also calculate the maximum wait time in OutputTrack::write() based the on smallest frame count of all output threads instead of the frame count of the thread the OutputTrack is connected to. This avoids starving the thread with the smallest frame count by waiting too long on the other thread.
Since the frame count was reduced on hardware output to reduce latency the difference between A2DP and hardware outputs frame counts had become problematic.
Also increased the number of overflow buffers to cope with bigger timing differences among outputs.

libs/audioflinger/AudioFlinger.h

diff --git a/libs/audioflinger/AudioFlinger.h b/libs/audioflinger/AudioFlinger.h
index 8c29da85..12c90eb 100644
--- a/libs/audioflinger/AudioFlinger.h
+++ b/libs/audioflinger/AudioFlinger.h
@@ -20,6 +20,7 @@
 
 #include <stdint.h>
 #include <sys/types.h>
+#include <limits.h>
 
 #include <media/IAudioFlinger.h>
 #include <media/IAudioFlingerClient.h>
@@ -208,6 +209,7 @@
     class PlaybackThread;
     class MixerThread;
     class DirectOutputThread;
+    class DuplicatingThread;
     class Track;
     class RecordTrack;
 
@@ -324,6 +326,7 @@
                     void        sendConfigEvent_l(int event, int param = 0);
                     void        processConfigEvents();
                     int         id() const { return mId;}
+                    bool        standby() { return mStandby; }
 
         mutable     Mutex                   mLock;
 
@@ -452,6 +455,7 @@
             };
 
                                 OutputTrack(  const wp<ThreadBase>& thread,
+                                        DuplicatingThread *sourceThread,
                                         uint32_t sampleRate,
                                         int format,
                                         int channelCount,
@@ -471,13 +475,12 @@
             void                clearBufferQueue();
 
             // Maximum number of pending buffers allocated by OutputTrack::write()
-            static const uint8_t kMaxOverFlowBuffers = 3;
+            static const uint8_t kMaxOverFlowBuffers = 10;
 
             Vector < Buffer* >          mBufferQueue;
             AudioBufferProvider::Buffer mOutBuffer;
-            uint32_t                    mWaitTimeMs;
             bool                        mActive;
-
+            DuplicatingThread*          mSourceThread;
         };  // end of OutputTrack
 
         PlaybackThread (const sp<AudioFlinger>& audioFlinger, AudioStreamOut* output, int id);
@@ -520,6 +523,7 @@
         virtual     int         type() const { return mType; }
                     void        suspend() { mSuspended++; }
                     void        restore() { if (mSuspended) mSuspended--; }
+                    bool        isSuspended() { return (mSuspended != 0); }
         virtual     String8     getParameters(const String8& keys);
         virtual     void        audioConfigChanged(int event, int param = 0);
 
@@ -635,9 +639,16 @@
         virtual     bool        threadLoop();
                     void        addOutputTrack(MixerThread* thread);
                     void        removeOutputTrack(MixerThread* thread);
+                    uint32_t    waitTimeMs() { return mWaitTimeMs; }
+    protected:
+        virtual     uint32_t    activeSleepTimeUs();
 
     private:
+                    bool        outputsReady(SortedVector< sp<OutputTrack> > &outputTracks);
+                    void        updateWaitTime();
+
         SortedVector < sp<OutputTrack> >  mOutputTracks;
+                    uint32_t    mWaitTimeMs;
     };
 
               PlaybackThread *checkPlaybackThread_l(int output) const;