output_device_mixer_impl.h | Explore in Territory

// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SERVICES_AUDIO_OUTPUT_DEVICE_MIXER_IMPL_H_
#define SERVICES_AUDIO_OUTPUT_DEVICE_MIXER_IMPL_H_

#include <memory>
#include <set>
#include <string>

#include "base/check.h"
#include "base/containers/unique_ptr_adapters.h"
#include "base/dcheck_is_on.h"
#include "base/functional/callback.h"
#include "base/memory/raw_ptr.h"
#include "base/synchronization/lock.h"
#include "base/timer/timer.h"
#include "media/audio/audio_io.h"
#include "media/base/audio_parameters.h"
#include "media/base/reentrancy_checker.h"
#include "services/audio/mixing_graph.h"
#include "services/audio/output_device_mixer.h"

namespace audio {
class MixingGraph;

// OutputDeviceMixerImpl manages the rendering of all output streams created by
// MakeMixableStream(). It has two rendering modes: if there
// are not listeners attached, each active output stream is rendered
// independently. If the mixer has listeners and at least one of the managed
// streams there is playing, all output streams are mixed by
// |mixing_graph_| and the result is played by |mixing_graph_output_stream_|.
// After mixing started, the mixed playback will stop only when the last
// listener is gone; this means the mixed playback will continue even when there
// are no managed streams playing. That is done because the listeners do not
// like when the reference signal stops and then starts again: it can cause
// reference signal delay jumps. TODO(olka): add metrics for how often/how long
// we may have listeners forsing such silent mixed playback.
class OutputDeviceMixerImpl final : public OutputDeviceMixer { … };

}  // namespace audio

#endif  // SERVICES_AUDIO_OUTPUT_DEVICE_MIXER_IMPL_H_
chromium/services/audio/output_device_mixer_impl.h
