Using native sampling rate and optimal buffer size for audio on Android.

media/audio/android/audio_manager_android.cc

Index: media/audio/android/audio_manager_android.cc
===================================================================
--- media/audio/android/audio_manager_android.cc	(revision 200599)
+++ media/audio/android/audio_manager_android.cc	(working copy)
@@ -22,6 +22,8 @@
 static const int kAudioModeNormal = 0x00000000;
 static const int kAudioModeInCommunication = 0x00000003;
 
+static const int kDefaultBufferSize = 2048;
+
 AudioManager* CreateAudioManager() {
   return new AudioManagerAndroid();
 }
@@ -56,13 +58,12 @@
 
 AudioParameters AudioManagerAndroid::GetInputStreamParameters(
     const std::string& device_id) {
-  // TODO(leozwang): Android defines the minimal buffer size requirment
-  // we should use it.
   static const int kDefaultBufferSize = 1024;

[Raymond Toy (Google), 2013/05/21 16:30:38]

This is kind of confusing since it has the same name but different value from
the definition at line 25.  Should the name be changed, either here or line 25?

[leozwang1, 2013/05/21 17:03:31]

Done.

-  // TODO(xians): query the native channel layout for the specific device.
+  int buffer_size = GetMinInputFrameSize(GetNativeOutputSampleRate(), 2);
   return AudioParameters(
       AudioParameters::AUDIO_PCM_LOW_LATENCY, CHANNEL_LAYOUT_STEREO,
-      GetNativeOutputSampleRate(), 16, kDefaultBufferSize);
+      GetNativeOutputSampleRate(), 16,
+      buffer_size <= 0 ? kDefaultBufferSize : buffer_size);
 }
 
 AudioOutputStream* AudioManagerAndroid::MakeAudioOutputStream(
@@ -119,15 +120,25 @@
   return new OpenSLESInputStream(this, params);
 }
 
+int AudioManagerAndroid::GetOptimalOutputFrameSize(int sample_rate,
+                                                        int channels) {
+  const int kDefaultBufferSize = 2048;

[Raymond Toy (Google), 2013/05/21 16:30:38]

Shouldn't this be removed now?

[leozwang1, 2013/05/21 17:03:31]

Done.

[leozwang1, 2013/05/21 17:03:31]

Done.

+  if (IsAudioLowLatencySupported()) {
+    int frame_size = GetAudioLowLatencyFrameSize();
+    // Return the optimal size as a multiple of the low latency frame
+    // size that is close to the target frame size.
+    return ((kDefaultBufferSize + frame_size / 2) / frame_size) * frame_size;
+  } else {
+    return std::max(kDefaultBufferSize,
+                    GetMinOutputFrameSize(sample_rate, channels));
+  }
+}
+
 AudioParameters AudioManagerAndroid::GetPreferredOutputStreamParameters(
     const AudioParameters& input_params) {
-  // TODO(leozwang): Android defines the minimal buffer size requirment
-  // we should use it.
-  static const int kDefaultBufferSize = 2048;
-
   ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   int sample_rate = GetNativeOutputSampleRate();
-  int buffer_size = kDefaultBufferSize;
+  int buffer_size = GetOptimalOutputFrameSize(sample_rate, 2);
   int bits_per_sample = 16;
   int input_channels = 0;
   if (input_params.IsValid()) {
@@ -136,8 +147,6 @@
     bits_per_sample = input_params.bits_per_sample();
     channel_layout = input_params.channel_layout();
     input_channels = input_params.input_channels();
-
-    buffer_size = std::min(buffer_size, input_params.frames_per_buffer());
   }
 
   int user_buffer_size = GetUserBufferSize();
@@ -178,4 +187,31 @@
       j_audio_manager_.obj());
 }
 
+int AudioManagerAndroid::GetMinInputFrameSize(int rate, int channels) {
+  // Java_AudioManagerAndroid_getMinInputBufSize return buffer size in bytes,
+  // convert it to size in frame.
+  return Java_AudioManagerAndroid_getMinInputBufSize(
+      base::android::AttachCurrentThread(), rate, channels) /
+      sizeof(int16) / channels;
+}
+
+int AudioManagerAndroid::GetMinOutputFrameSize(int rate, int channels) {
+  // Get buffer size in frames, assuming 16-bit pcm samples.
+  return Java_AudioManagerAndroid_getMinOutputBufSize(
+      base::android::AttachCurrentThread(), rate, channels) /
+      sizeof(int16) / channels;
+}
+
+bool AudioManagerAndroid::IsAudioLowLatencySupported() {
+  return Java_AudioManagerAndroid_isAudioLowLatencySupported(
+      base::android::AttachCurrentThread(),
+      j_audio_manager_.obj());
+}
+
+int AudioManagerAndroid::GetAudioLowLatencyFrameSize() {
+  return Java_AudioManagerAndroid_getAudioLowLatencyFrameSize(
+      base::android::AttachCurrentThread(),
+      j_audio_manager_.obj());
+}
+
 }  // namespace media