Enable low latency mode for audio playback on Android

media/audio/android/audio_manager_android.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/android/audio_manager_android.h"
 
 #include "base/logging.h"
 #include "jni/AudioManagerAndroid_jni.h"
 #include "media/audio/android/opensles_input.h"
 #include "media/audio/android/opensles_output.h"
@@ skipping 108 matching lines @@
 AudioInputStream* AudioManagerAndroid::MakeLowLatencyInputStream(
     const AudioParameters& params, const std::string& device_id) {
   DCHECK_EQ(AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
   return new OpenSLESInputStream(this, params);
 }
 
 int AudioManagerAndroid::GetOptimalOutputFrameSize(int sample_rate,
                                                    int channels) {
   if (IsAudioLowLatencySupported()) {
     int frame_size = GetAudioLowLatencyOutputFrameSize();
     // Return the optimal size as a multiple of the low latency frame

[DaleCurtis, 2013/06/17 21:49:53]

Also delete this comment and just return  GetAudioLowLatencyOutputFrameSize();
directly too.

[wjia(left Chromium), 2013/06/17 22:04:10]

Done.

     // size that is close to the target frame size.
-    return ((kDefaultOutputBufferSize + frame_size / 2) / frame_size) *
-      frame_size;
+    return frame_size;
   } else {
     return std::max(kDefaultOutputBufferSize,
                     Java_AudioManagerAndroid_getMinOutputFrameSize(
                         base::android::AttachCurrentThread(),
                         sample_rate, channels));
   }
 }
 
 AudioParameters AudioManagerAndroid::GetPreferredOutputStreamParameters(
     const AudioParameters& input_params) {
@@ skipping 55 matching lines @@
       j_audio_manager_.obj());
 }
 
 int AudioManagerAndroid::GetAudioLowLatencyOutputFrameSize() {
   return Java_AudioManagerAndroid_getAudioLowLatencyOutputFrameSize(
       base::android::AttachCurrentThread(),
       j_audio_manager_.obj());
 }
 
 }  // namespace media