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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_INPUT_STREAM_IMPL_H_
#define MEDIA_AUDIO_AUDIO_INPUT_STREAM_IMPL_H_
#include "base/compiler_specific.h"
#include "base/synchronization/lock.h"
#include "base/time.h"
#include "media/audio/audio_io.h"
namespace media {
// AudioInputStreamImpl implements platform-independent parts of the
// AudioInputStream interface. Each platform dependent implementation
// should derive from this class.
// TODO(henrika): we can probably break out more parts from our current
// AudioInputStream implementation and move out to this class.
class MEDIA_EXPORT AudioInputStreamImpl : public AudioInputStream {
public:
AudioInputStreamImpl();
virtual ~AudioInputStreamImpl();
// Sets the automatic gain control (AGC) to on or off. When AGC is enabled,
// the microphone volume is queried periodically and the volume level is
// provided in each AudioInputCallback::OnData() callback and fed to the
// render-side AGC.
virtual void SetAutomaticGainControl(bool enabled) OVERRIDE;
// Gets the current automatic gain control state.
virtual bool GetAutomaticGainControl() OVERRIDE;
protected:
// Stores a new volume level by asking the audio hardware.
// This method only has an effect if AGC is enabled.
void UpdateAgcVolume();
// Gets the latest stored volume level if AGC is enabled and if
// more than one second has passed since the volume was updated the last time.
void QueryAgcVolume(double* normalized_volume);
private:
// Takes a volume sample and stores it in |normalized_volume_|.
void GetNormalizedVolume();
// True when automatic gain control is enabled, false otherwise.
// Guarded by |lock_|.
bool agc_is_enabled_;
// Stores the maximum volume which is used for normalization to a volume
// range of [0.0, 1.0].
double max_volume_;
// Contains last result of internal call to GetVolume(). We save resources
// but not querying the capture volume for each callback. Guarded by |lock_|.
// The range is normalized to [0.0, 1.0].
double normalized_volume_;
// Protects |agc_is_enabled_| and |volume_| .
base::Lock lock_;
// Keeps track of the last time the microphone volume level was queried.
base::Time last_volume_update_time_;
DISALLOW_COPY_AND_ASSIGN(AudioInputStreamImpl);
};
} // namespace media
#endif // MEDIA_AUDIO_AUDIO_INPUT_STREAM_IMPL_H_
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