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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.
#include <stdint.h>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "base/atomic_ref_count.h"
#include "base/callback.h"
#include "base/containers/flat_set.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/optional.h"
#include "base/strings/string_piece.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/audio/audio_power_monitor.h"
#include "media/audio/audio_source_diverter.h"
#include "services/audio/loopback_group_member.h"
#include "services/audio/stream_monitor_coordinator.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,
public media::AudioManager::AudioDeviceListener,
public StreamMonitorCoordinator::Observer {
// An event handler that receives events from the OutputController. The
// following methods are called on the audio manager thread.
class EventHandler {
virtual void OnControllerPlaying() = 0;
virtual void OnControllerPaused() = 0;
virtual void OnControllerError() = 0;
virtual void OnLog(base::StringPiece message) = 0;
virtual ~EventHandler() {}
// A synchronous reader interface used by OutputController for synchronous
// reading.
// TODO(crogers): find a better name for this class and the Read() method
// now that it can handle synchronized I/O.
class SyncReader {
virtual ~SyncReader() {}
// This is used by SyncReader to prepare more data and perform
// synchronization. Also inform about output delay at a certain moment and
// if any frames have been skipped by the renderer (typically the OS). The
// renderer source can handle this appropriately depending on the type of
// source. An ordinary file playout would ignore this.
virtual void RequestMoreData(base::TimeDelta delay,
base::TimeTicks delay_timestamp,
int prior_frames_skipped) = 0;
// Attempts to completely fill |dest|, zeroing |dest| if the request can not
// be fulfilled (due to timeout).
virtual void Read(media::AudioBus* dest) = 0;
// Close this synchronous reader.
virtual void Close() = 0;
// |audio_manager| and |handler| must outlive OutputController. The
// |output_device_id| can be either empty (default device) or specify a
// specific hardware device for audio output.
OutputController(media::AudioManager* audio_manager,
EventHandler* handler,
const media::AudioParameters& params,
const std::string& output_device_id,
SyncReader* sync_reader,
StreamMonitorCoordinator* stream_monitor_coordinator,
const base::UnguessableToken& processing_id);
~OutputController() override;
// Indicates whether audio power level analysis will be performed. If false,
// ReadCurrentPowerAndClip() can not be called.
static constexpr bool will_monitor_audio_levels() {
#if defined(OS_ANDROID) || defined(OS_IOS)
return false;
return true;
// Methods to control playback of the stream.
// Creates the audio output stream. This must be called before Play(). Returns
// true if successful, and Play() may commence.
bool CreateStream();
// Starts the playback of this audio output stream.
void Play();
// Pause this audio output stream.
void Pause();
// Closes the audio output stream synchronously. Stops the stream first, if
// necessary. After this method returns, this OutputController can be
// destroyed by its owner.
void Close();
// Sets the volume of the audio output stream.
void SetVolume(double volume);
// AudioSourceCallback implementation.
int OnMoreData(base::TimeDelta delay,
base::TimeTicks delay_timestamp,
int prior_frames_skipped,
media::AudioBus* dest) override;
void OnError() override;
// LoopbackGroupMember implementation.
const media::AudioParameters& GetAudioParameters() const override;
std::string GetDeviceId() const override;
void StartSnooping(Snooper* snooper, SnoopingMode mode) override;
void StopSnooping(Snooper* snooper, SnoopingMode mode) override;
void StartMuting() override;
void StopMuting() override;
// StreamMonitorCoordinator::Observer implementation.
void OnMemberJoinedGroup(StreamMonitor* monitor) override;
void OnMemberLeftGroup(StreamMonitor* monitor) override;
// AudioDeviceListener implementation. When called OutputController will
// shutdown the existing |stream_|, create a new stream, and then transition
// back to an equivalent state prior to being called.
void OnDeviceChange() override;
// Accessor for AudioPowerMonitor::ReadCurrentPowerAndClip(). See comments in
// audio_power_monitor.h for usage. This may be called on any thread.
std::pair<float, bool> ReadCurrentPowerAndClip();
// Internal state of the source.
enum State {
// Time constant for AudioPowerMonitor. See AudioPowerMonitor ctor comments
// for semantics. This value was arbitrarily chosen, but seems to work well.
enum { kPowerMeasurementTimeConstantMillis = 10 };
// Possible reasons for calling RecreateStream().
enum class RecreateReason : int8_t {
// Used to store various stats about a stream. The lifetime of this object is
// from play until pause. The underlying physical stream may be changed when
// resuming playback, hence separate stats are logged for each play/pause
// cycle.
class ErrorStatisticsTracker {
// Note: the destructor takes care of logging all of the stats.
// Called to indicate an error callback was fired for the stream.
void RegisterError();
// This function should be called from the stream callback thread.
void OnMoreDataCalled();
void WedgeCheck();
const base::TimeTicks start_time_;
bool error_during_callback_ = false;
// Flags when we've asked for a stream to start but it never did.
base::AtomicRefCount on_more_io_data_called_;
base::OneShotTimer wedge_timer_;
// Helper to call RecreateStream(), but with a scoped "CreateTime" UMA timing
// measurement surrounding the call.
void RecreateStreamWithTimingUMA(RecreateReason reason);
// Closes the current stream and re-creates a new one via the AudioManager. If
// reason is LOCAL_OUTPUT_TOGGLE, the new stream will be a fake one and UMA
// counts will not be incremented.
void RecreateStream(RecreateReason reason);
// Notifies the EventHandler that an error has occurred.
void ReportError();
// Helper method that stops the physical stream.
void StopStream();
// Helper method that stops, closes, and NULLs |*stream_|.
void StopCloseAndClearStream();
// Send audio data to each Snooper.
void BroadcastDataToSnoopers(std::unique_ptr<media::AudioBus> audio_bus,
base::TimeTicks reference_time);
// Log the current average power level measured by power_monitor_.
void LogAudioPowerLevel(const char* call_name);
// Helper called by StartMuting() and StopMuting() to execute the stream
// change.
void ToggleLocalOutput();
media::AudioManager* const audio_manager_;
const media::AudioParameters params_;
EventHandler* const handler_;
// The task runner for the audio manager. All control methods should be called
// via tasks run by this TaskRunner.
const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
// Time when the controller is constructed. Used to record its lifetime on
// destruction.
const base::TimeTicks construction_time_;
// Specifies the device id of the output device to open or empty for the
// default output device.
const std::string output_device_id_;
media::AudioOutputStream* stream_;
// When true, local audio output should be muted; either by having audio
// diverted to |diverting_to_stream_|, or a fake AudioOutputStream.
bool disable_local_output_;
// The targets for audio stream to be copied to. |should_duplicate_| is set to
// 1 when the OnMoreData() call should proxy the data to
// BroadcastDataToSnoopers().
std::vector<Snooper*> snoopers_;
base::AtomicRefCount should_duplicate_;
base::Lock realtime_snooper_lock_;
std::vector<Snooper*> realtime_snoopers_;
// The current volume of the audio stream.
double volume_;
State state_;
// SyncReader is used only in low latency mode for synchronous reading.
SyncReader* const sync_reader_;
StreamMonitorCoordinator* const stream_monitor_coordinator_;
base::UnguessableToken const processing_id_;
// Scans audio samples from OnMoreData() as input to compute power levels.
media::AudioPowerMonitor power_monitor_;
// Updated each time a power measurement is logged.
base::TimeTicks last_audio_level_log_time_;
// Used for keeping track of and logging stats. Created when a stream starts
// and destroyed when a stream stops. Also reset every time there is a stream
// being created due to device changes.
base::Optional<ErrorStatisticsTracker> stats_tracker_;
// WeakPtrFactory+WeakPtr that is used to post tasks that are canceled when a
// stream is closed.
base::WeakPtr<OutputController> weak_this_for_stream_;
base::WeakPtrFactory<OutputController> weak_factory_for_stream_;
} // namespace audio