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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_
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