Support (E)AC3 passthrough

media/audio/android/audio_track_output_stream.h

+// Copyright 2017 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.
+
+#ifndef MEDIA_AUDIO_ANDROID_AUDIO_TRACK_OUTPUT_STREAM_H_
+#define MEDIA_AUDIO_ANDROID_AUDIO_TRACK_OUTPUT_STREAM_H_
+
+#include <memory>
+
+#include "base/android/jni_android.h"
+#include "base/time/tick_clock.h"
+#include "media/audio/android/muteable_audio_output_stream.h"
+#include "media/base/audio_parameters.h"
+
+namespace media {
+
+class AudioManagerBase;
+
+// A MuteableAudioOutputStream implementation based on the Android AudioTrack
+// API.
+class MEDIA_EXPORT AudioTrackOutputStream : public MuteableAudioOutputStream {
+ public:
+  AudioTrackOutputStream(AudioManagerBase* manager,
+                         const AudioParameters& params);
+  ~AudioTrackOutputStream() override;
+
+  // AudioOutputStream implementation.
+  bool Open() override;
+  void Start(AudioSourceCallback* callback) override;
+  void Stop() override;
+  void SetVolume(double volume) override;
+  void GetVolume(double* volume) override;
+  void Close() override;
+
+  // MuteableAudioOutputStream implementation.
+  void SetMute(bool muted) override;
+
+  // JNI registry.
+  static bool RegisterAudioTrackOutputStream(JNIEnv* env);
+
+  // AudioOutputStream::SourceCallback implementation methods called from Java.
+  int OnMoreData(JNIEnv* env, jobject obj, jobject audio_data, int delay);
+  void OnError(JNIEnv* env, jobject obj);
+
+ private:
+  const AudioParameters params_;
+
+  AudioManagerBase* audio_manager_;
+  AudioSourceCallback* callback_;
+  std::unique_ptr<AudioBus> audio_bus_;
+  bool muted_;
+  double volume_;
+  int total_read_frames_;

[chcunningham, 2017/06/14 20:27:21]

At sample rate of 44.1 you can only do about 13 hours of playback before this
overflows. Thats a lot of playback, but given that this is for TVs I'd say its
possible you'll see it happen. I'd use an int64 here. 

[AndyWu, 2017/08/02 01:43:39]

Done.

+
+  std::unique_ptr<base::TickClock> tick_clock_;
+
+  // Java AudioTrackOutputStream instance.
+  base::android::ScopedJavaGlobalRef<jobject> j_audio_output_stream_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioTrackOutputStream);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_ANDROID_AUDIO_TRACK_OUTPUT_STREAM_H_