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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.
#ifndef MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_
#define MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_
#include <map>
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "media/audio/audio_io.h"
#include "media/audio/audio_manager.h"
#include "media/audio/audio_output_dispatcher_impl.h"
#include "media/audio/audio_parameters.h"
namespace media {
class OnMoreDataConverter;
// AudioOutputResampler is a browser-side resampling and buffering solution
// which ensures audio data is always output at given parameters. See the
// AudioConverter class for details on the conversion process.
//
// AOR works by intercepting the AudioSourceCallback provided to StartStream()
// and redirecting it through an AudioConverter instance. |total_bytes_delay|
// is adjusted for buffer delay caused by the conversion process.
//
// AOR will automatically fall back from AUDIO_PCM_LOW_LATENCY to
// AUDIO_PCM_LINEAR if the output device fails to open at the requested output
// parameters. If opening still fails, it will fallback to AUDIO_FAKE.
class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher {
public:
AudioOutputResampler(AudioManager* audio_manager,
const AudioParameters& input_params,
const AudioParameters& output_params,
const std::string& output_device_id,
const base::TimeDelta& close_delay);
// AudioOutputDispatcher interface.
bool OpenStream() override;
bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
AudioOutputProxy* stream_proxy) override;
void StopStream(AudioOutputProxy* stream_proxy) override;
void StreamVolumeSet(AudioOutputProxy* stream_proxy, double volume) override;
void CloseStream(AudioOutputProxy* stream_proxy) override;
void Shutdown() override;
private:
friend class base::RefCountedThreadSafe<AudioOutputResampler>;
~AudioOutputResampler() override;
// Converts low latency based output parameters into high latency
// appropriate output parameters in error situations.
void SetupFallbackParams();
// Used to reinitialize |dispatcher_|.
void Reinitialize();
// Used to initialize |dispatcher_|.
void Initialize();
// Dispatcher to proxy all AudioOutputDispatcher calls too.
scoped_refptr<AudioOutputDispatcherImpl> dispatcher_;
// Map of outstanding OnMoreDataConverter objects. A new object is created
// on every StartStream() call and destroyed on CloseStream().
typedef std::map<AudioOutputProxy*, OnMoreDataConverter*> CallbackMap;
CallbackMap callbacks_;
// Used by AudioOutputDispatcherImpl; kept so we can reinitialize on the fly.
base::TimeDelta close_delay_;
// AudioParameters used to setup the output stream; changed upon fallback.
AudioParameters output_params_;
// The original AudioParameters we were constructed with.
const AudioParameters original_output_params_;
// Whether any streams have been opened through |dispatcher_|, if so we can't
// fallback on future OpenStream() failures.
bool streams_opened_;
// The reinitialization timer provides a way to recover from temporary failure
// states by clearing the dispatcher if all proxies have been closed and none
// have been created within |close_delay_|. Without this, audio may be lost
// to a fake stream indefinitely for transient errors.
base::Timer reinitialize_timer_;
DISALLOW_COPY_AND_ASSIGN(AudioOutputResampler);
};
} // namespace media
#endif // MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_
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