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

media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java

Index: media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
diff --git a/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java b/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
index 9066380d62c230dc9fd74c632085e0d991794746..5b51c012d006fa54af8f424e32c26f75068e3032 100644
--- a/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
+++ b/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
@@ -8,7 +8,11 @@ import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.content.pm.PackageManager;
+import android.media.AudioFormat;
 import android.media.AudioManager;
+import android.media.AudioRecord;
+import android.media.AudioTrack;
 import android.os.Build;
 import android.util.Log;
 
@@ -18,6 +22,10 @@ import org.chromium.base.JNINamespace;
 @JNINamespace("media")
 class AudioManagerAndroid {
     private static final String TAG = AudioManagerAndroid.class.getSimpleName();
+    // Most of Google lead devices use 44.1K as the default sampling rate, 44.1K
+    // is also widely used on other android devices.
+    private static final int DEFAULT_SAMPLING_RATE = 44100;
+    private static final int DEFAULT_FRAME_PER_BUFFER = 256;
 
     private final AudioManager mAudioManager;
     private final Context mContext;
@@ -83,4 +91,57 @@ class AudioManagerAndroid {
                   " Board: " + Build.BOARD + " Device: " + Build.DEVICE +
                   " Model: " + Build.MODEL + " PRODUCT: " + Build.PRODUCT);
     }
+
+    @CalledByNative
+    private int getNativeOutputSampleRate() {
+        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN_MR1) {
+            String sampleRateString = mAudioManager.getProperty(
+                    AudioManager.PROPERTY_OUTPUT_SAMPLE_RATE);
+            return (sampleRateString == null ?
+                    DEFAULT_SAMPLING_RATE : Integer.parseInt(sampleRateString));
+        } else {
+            return DEFAULT_SAMPLING_RATE;
+        }
+    }
+
+    @CalledByNative
+    private static int getMinInputBufSize(int sampleRate, int channels) {
+        int channelConfig;
+        if (channels == 1)
+            channelConfig = AudioFormat.CHANNEL_IN_MONO;
+        else if (channels == 2)
+            channelConfig = AudioFormat.CHANNEL_IN_STEREO;
+        else
+            return -1;
+        return AudioRecord.getMinBufferSize(sampleRate, channelConfig,
+                                            AudioFormat.ENCODING_PCM_16BIT);
+    }
+
+    @CalledByNative
+    private static int getMinOutputBufSize(int sampleRate, int channels) {
+        int channelConfig;
+        if (channels == 1)
+            channelConfig = AudioFormat.CHANNEL_OUT_MONO;
+        else if (channels == 2)
+            channelConfig = AudioFormat.CHANNEL_OUT_STEREO;
+        else
+            return -1;
+        return AudioTrack.getMinBufferSize(sampleRate, channelConfig,
+                                           AudioFormat.ENCODING_PCM_16BIT);
+    }
+
+    @CalledByNative
+    private boolean isAudioLowLatencySupported() {
+        return mContext.getPackageManager().hasSystemFeature(
+                PackageManager.FEATURE_AUDIO_LOW_LATENCY);
+    }
+
+    @CalledByNative
+    private int getAudioLowLatencyFrameSize() {
+        String framesPerBuffer =
+                mAudioManager.getProperty(AudioManager.PROPERTY_OUTPUT_FRAMES_PER_BUFFER);
+        return (framesPerBuffer == null ?
+                DEFAULT_FRAME_PER_BUFFER : Integer.parseInt(framesPerBuffer));
+    }
+
 }