Improvements for issue 2197683: English IME key-press latency is noticeably higher on passion than sholes

This change goes with a kernel driver change that reduces the audio buffer size from 4800 bytes (~27ms) to 3072 bytes (~17ms).
- The AudioFlinger modifcations in change 0bca68cfff161abbc992fec82dc7c88079dd1a36 have been removed: the short sleep period was counter productive when the AudioTrack is using the call back thread as it causes to many preemptions.
- AudioFlinger mixer thread now detects long standby exit time and in this case anticipates start by writing 0s as soon as a track is enabled even if not ready for mixing.
- AudioTrack::start() is modified to start call back thread before starting the IAudioTrack so that thread startup time is masked by IAudioTrack start and mixer thread wakeup time.

1 files changed, 18 insertions, 9 deletions

diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index 8529a8e..cedd79d 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -318,26 +318,35 @@ void AudioTrack::start()
      }
 
     if (android_atomic_or(1, &mActive) == 0) {
-        audio_io_handle_t output = AudioTrack::getOutput();
+        audio_io_handle_t output = getOutput();
+        AudioSystem::startOutput(output, (AudioSystem::stream_type)mStreamType);
+        mNewPosition = mCblk->server + mUpdatePeriod;
+        mCblk->bufferTimeoutMs = MAX_STARTUP_TIMEOUT_MS;
+        mCblk->waitTimeMs = 0;
+        if (t != 0) {
+           t->run("AudioTrackThread", THREAD_PRIORITY_AUDIO_CLIENT);
+        } else {
+            setpriority(PRIO_PROCESS, 0, THREAD_PRIORITY_AUDIO_CLIENT);
+        }
+
         status_t status = mAudioTrack->start();
         if (status == DEAD_OBJECT) {
             LOGV("start() dead IAudioTrack: creating a new one");
             status = createTrack(mStreamType, mCblk->sampleRate, mFormat, mChannelCount,
                                  mFrameCount, mFlags, mSharedBuffer, output);
-        }
-        if (status == NO_ERROR) {
-            AudioSystem::startOutput(output, (AudioSystem::stream_type)mStreamType);
             mNewPosition = mCblk->server + mUpdatePeriod;
             mCblk->bufferTimeoutMs = MAX_STARTUP_TIMEOUT_MS;
             mCblk->waitTimeMs = 0;
+        }
+        if (status != NO_ERROR) {
+            LOGV("start() failed");
+            android_atomic_and(~1, &mActive);
             if (t != 0) {
-               t->run("AudioTrackThread", THREAD_PRIORITY_AUDIO_CLIENT);
+                t->requestExit();
             } else {
-                setpriority(PRIO_PROCESS, 0, THREAD_PRIORITY_AUDIO_CLIENT);
+                setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_NORMAL);
             }
-        } else {
-            LOGV("start() failed");
-            android_atomic_and(~1, &mActive);
+            AudioSystem::stopOutput(output, (AudioSystem::stream_type)mStreamType);
         }
     }