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diff --git a/media/audio/linux/cras_output.h b/media/audio/linux/cras_output.h
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+++ b/media/audio/linux/cras_output.h
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+// 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.
+//
+// Creates an output stream based on the cras (ChromeOS audio server) interface.
+//
+// CrasOutputStream object is *not* thread-safe and should only be used
+// from the audio thread.
+
+#ifndef MEDIA_AUDIO_LINUX_CRAS_OUTPUT_H_
+#define MEDIA_AUDIO_LINUX_CRAS_OUTPUT_H_
+
+#include <alsa/asoundlib.h>
+#include <cras_client.h>
+#include <ostream>
+
+#include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
+#include "media/audio/audio_io.h"
+
+class AudioManagerLinux;
+class AudioParameters;
+
+// Implementation of AudioOuputStream for Chrome OS using the Chrome OS audio
+// server.
+class MEDIA_EXPORT CrasOutputStream : public AudioOutputStream {
+ public:
+  // The ctor takes all the usual parameters, plus |manager| which is the
+  // audio manager who is creating this object.
+  CrasOutputStream(const AudioParameters& params, AudioManagerLinux* manager);
+
+  // The dtor is typically called by the AudioManager only and it is usually
+  // triggered by calling AudioOutputStream::Close().
+  virtual ~CrasOutputStream();
+
+  // Implementation of AudioOutputStream.
+  virtual bool Open() OVERRIDE;
+  virtual void Close() OVERRIDE;
+  virtual void Start(AudioSourceCallback* callback) OVERRIDE;
+  virtual void Stop() OVERRIDE;
+  virtual void SetVolume(double volume) OVERRIDE;
+  virtual void GetVolume(double* volume) OVERRIDE;
+
+  // Flags indicating the state of the stream.
+  enum InternalState {
+    kInError = 0,
+    kCreated,
+    kIsOpened,
+    kIsPlaying,
+    kIsStopped,
+    kIsClosed
+  };
+  friend std::ostream& operator<<(std::ostream& os, InternalState);
+  // Reports the current state for unit testing.
+  InternalState state();
+
+ private:
+  // Handles requests to put samples in the provided buffer.  This will be
+  // called by the audio server when it needs more data.
+  static int PutSamples(cras_client* client,
+                        cras_stream_id_t stream_id,
+                        uint8* samples,
+                        size_t frames,
+                        const timespec* sample_ts,
+                        void* arg);
+
+  // Handles notificaiton that there was an error with the playback stream.
+  static int StreamError(cras_client* client,
+                         cras_stream_id_t stream_id,
+                         int err,
+                         void* arg);
+
+  // Actually fills buffer with audio data.  Called from PutSamples().
+  uint32 Render(size_t frames, uint8* buffer, const timespec* sample_ts);
+
+  // Deals with an error that occured in the stream.  Called from StreamError().
+  void NotifyStreamError(int err);
+
+  // Functions to safeguard state transitions.  All changes to the object state
+  // should go through these functions.
+  bool CanTransitionTo(InternalState to);
+  InternalState TransitionTo(InternalState to);
+
+  // The client used to communicate with the audio server.
+  cras_client* client_;
+
+  // ID of the playing stream.
+  cras_stream_id_t stream_id_;
+
+  // Packet size in samples.
+  uint32 samples_per_packet_;
+
+  // Rate in Hz.
+  size_t frame_rate_;
+
+  // Number of channels.
+  size_t num_channels_;
+
+  // PCM format for Alsa.
+  const snd_pcm_format_t pcm_format_;
+
+  // Current state.
+  InternalState state_;
+
+  // Volume level from 0.0 to 1.0.
+  float volume_;
+
+  // Audio manager that created us.  Used to report that we've been closed.
+  AudioManagerLinux* manager_;
+
+  // Callback to get audio samples.
+  AudioSourceCallback* source_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(CrasOutputStream);
+};
+
+#endif  // MEDIA_AUDIO_LINUX_CRAS_OUTPUT_H_