output_controller.h | Explore in Territory

// Copyright 2012 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_CONTROLLER_H_
#define SERVICES_AUDIO_OUTPUT_CONTROLLER_H_

#include <stdint.h>

#include <memory>
#include <optional>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#include "base/atomic_ref_count.h"
#include "base/compiler_specific.h"
#include "base/functional/callback.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ptr_exclusion.h"
#include "base/task/single_thread_task_runner.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "base/unguessable_token.h"
#include "build/build_config.h"
#include "media/audio/audio_io.h"
#include "media/audio/audio_manager.h"
#include "media/base/audio_power_monitor.h"
#include "services/audio/loopback_group_member.h"

// An OutputController controls an AudioOutputStream and provides data to this
// output stream. It executes audio operations like play, pause, stop, etc. on
// the audio manager thread, while the audio data flow occurs on the platform's
// realtime audio thread.
//
// Here is a state transition diagram for the OutputController:
//
//   *[ Empty ]  -->  [ Created ]  -->  [ Playing ]  -------.
//        |                |               |    ^           |
//        |                |               |    |           |
//        |                |               |    |           v
//        |                |               |    `-----  [ Paused ]
//        |                |               |                |
//        |                v               v                |
//        `----------->  [      Closed       ]  <-----------'
//
// * Initial state
//
// At any time after reaching the Created state but before Closed, the
// OutputController may be notified of a device change via OnDeviceChange().  As
// the OnDeviceChange() is processed, state transitions will occur, ultimately
// ending up in an equivalent pre-call state.  E.g., if the state was Paused,
// the new state will be Created, since these states are all functionally
// equivalent and require a Play() call to continue to the next state.
//
// The AudioOutputStream can request data from the OutputController via the
// AudioSourceCallback interface. OutputController uses the SyncReader passed to
// it via construction to synchronously fulfill this read request.

namespace audio {
class OutputController : public media::AudioOutputStream::AudioSourceCallback,
                         public LoopbackGroupMember { … };

}  // namespace audio

#endif  // SERVICES_AUDIO_OUTPUT_CONTROLLER_H_
chromium/services/audio/output_controller.h
