Add a unified audio I/O backend for ChromeOS.

media/audio/cras/cras_output.h

-// 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_CRAS_CRAS_OUTPUT_H_
-#define MEDIA_AUDIO_CRAS_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"
-
-namespace media {
-
-class AudioManagerCras;
-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, AudioManagerCras* 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_;
-
-  // Size of frame in bytes.
-  uint32 bytes_per_frame_;
-
-  // 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.
-  AudioManagerCras* manager_;
-
-  // Callback to get audio samples.
-  AudioSourceCallback* source_callback_;
-
-  // Container for retrieving data from AudioSourceCallback::OnMoreData().
-  scoped_ptr<AudioBus> audio_bus_;
-
-  DISALLOW_COPY_AND_ASSIGN(CrasOutputStream);
-};
-
-}  // namespace media
-
-#endif  // MEDIA_AUDIO_CRAS_CRAS_OUTPUT_H_