Fix slow playback of 1-channel MP3 and AAC files for WebAudio on Android

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

 // Copyright (c) 2013 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.
 
 package org.chromium.media;
 
 import android.content.Context;
 import android.media.AudioFormat;
 import android.media.MediaCodec;
 import android.media.MediaCodec.BufferInfo;
@@ skipping 43 matching lines @@
             return false;
         }
 
         if (extractor.getTrackCount() <= 0) {
             encodedFD.detachFd();
             return false;
         }
 
         MediaFormat format = extractor.getTrackFormat(0);
 
-        int channelCount = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
+        // Number of channels specified in the file
+        int inputChannelCount = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
+
+        // Number of channels the decoder will provide. (Not
+        // necessarily the same as inputChannelCount.  See
+        // crbug.com/266006.)
+        int outputChannelCount = inputChannelCount;
+
         int sampleRate = format.getInteger(MediaFormat.KEY_SAMPLE_RATE);
         String mime = format.getString(MediaFormat.KEY_MIME);
 
         long durationMicroseconds = 0;
         if (format.containsKey(MediaFormat.KEY_DURATION)) {
             try {
                 durationMicroseconds = format.getLong(MediaFormat.KEY_DURATION);
             } catch (Exception e) {
                 Log.d(LOG_TAG, "Cannot get duration");
             }
         }
 
         if (DEBUG) {
             Log.d(LOG_TAG, "Tracks: " + extractor.getTrackCount()
                   + " Rate: " + sampleRate
-                  + " Channels: " + channelCount
+                  + " Channels: " + inputChannelCount
                   + " Mime: " + mime
                   + " Duration: " + durationMicroseconds + " microsec");
         }
 
         nativeInitializeDestination(nativeMediaCodecBridge,
-                                    channelCount,
+                                    inputChannelCount,
                                     sampleRate,
                                     durationMicroseconds);
 
         // Create decoder
         MediaCodec codec = MediaCodec.createDecoderByType(mime);
         codec.configure(format, null /* surface */, null /* crypto */, 0 /* flags */);
         codec.start();
 
         ByteBuffer[] codecInputBuffers = codec.getInputBuffers();
         ByteBuffer[] codecOutputBuffers = codec.getOutputBuffers();
@@ skipping 35 matching lines @@
             }
 
             // Output side
             MediaCodec.BufferInfo info = new BufferInfo();
             final int outputBufIndex = codec.dequeueOutputBuffer(info, TIMEOUT_MICROSECONDS);
 
             if (outputBufIndex >= 0) {
                 ByteBuffer buf = codecOutputBuffers[outputBufIndex];
 
                 if (info.size > 0) {
-                    nativeOnChunkDecoded(nativeMediaCodecBridge, buf, info.size);
+                    nativeOnChunkDecoded(nativeMediaCodecBridge, buf, info.size,
+                                         inputChannelCount, outputChannelCount);
                 }
 
                 buf.clear();
                 codec.releaseOutputBuffer(outputBufIndex, false /* render */);
 
                 if ((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                     sawOutputEOS = true;
                 }
             } else if (outputBufIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
                 codecOutputBuffers = codec.getOutputBuffers();
+            } else if (outputBufIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
+                MediaFormat newFormat = codec.getOutputFormat();
+                outputChannelCount = newFormat.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
+                Log.d(LOG_TAG, "output format changed to " + newFormat);
             }
         }
 
         encodedFD.detachFd();
 
         codec.stop();
         codec.release();
         codec = null;
 
         return true;
     }
 
     private static native void nativeOnChunkDecoded(
-        int nativeWebAudioMediaCodecBridge, ByteBuffer buf, int size);
+        int nativeWebAudioMediaCodecBridge, ByteBuffer buf, int size,
+        int inputChannelCount, int outputChannelCount);
 
     private static native void nativeInitializeDestination(
         int nativeWebAudioMediaCodecBridge,
-        int channelCount,
+        int inputChannelCount,
         int sampleRate,
         long durationMicroseconds);
 }