blob: 057cf34b766c6701a6a5f7a88bcac68a490c0afd [file] [log] [blame]
// 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.
#include <map>
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/time.h"
#include "media/audio/audio_io.h"
#include "media/audio/audio_manager.h"
#include "media/audio/audio_output_dispatcher.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. AudioBuffersState 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.
// TODO(dalecurtis): Ideally the low latency path will be as reliable as the
// high latency path once we have channel mixing and support querying for the
// hardware's configured bit depth. Monitor the UMA stats for fallback and
// remove fallback support once it's stable.
class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher {
AudioOutputResampler(AudioManager* audio_manager,
const AudioParameters& input_params,
const AudioParameters& output_params,
const base::TimeDelta& close_delay);
// AudioOutputDispatcher interface.
virtual bool OpenStream() OVERRIDE;
virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
AudioOutputProxy* stream_proxy) OVERRIDE;
virtual void StopStream(AudioOutputProxy* stream_proxy) OVERRIDE;
virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
double volume) OVERRIDE;
virtual void CloseStream(AudioOutputProxy* stream_proxy) OVERRIDE;
virtual void Shutdown() OVERRIDE;
friend class base::RefCountedThreadSafe<AudioOutputResampler>;
virtual ~AudioOutputResampler();
// Used to initialize and reinitialize |dispatcher_|.
void Initialize();
// Dispatcher to proxy all AudioOutputDispatcher calls too.
scoped_refptr<AudioOutputDispatcher> 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.
AudioParameters output_params_;
// Whether any streams have been opened through |dispatcher_|, if so we can't
// fallback on future OpenStream() failures.
bool streams_opened_;
} // namespace media