/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this file, * You can obtain one at http://mozilla.org/MPL/2.0/. */ #ifndef GRAPHDRIVER_H_ #define GRAPHDRIVER_H_ #include "nsAutoRef.h" #include "AudioBufferUtils.h" #include "AudioMixer.h" #include "AudioSegment.h" #include "SelfRef.h" #include "mozilla/Atomics.h" #include "mozilla/SharedThreadPool.h" #include "mozilla/StaticPtr.h" struct cubeb_stream; template <> class nsAutoRefTraits<cubeb_stream> : public nsPointerRefTraits<cubeb_stream> { public: static void Release(cubeb_stream* aStream) { cubeb_stream_destroy(aStream); } }; namespace mozilla { /** * Assume we can run an iteration of the MediaStreamGraph loop in this much time * or less. * We try to run the control loop at this rate. */ static const int MEDIA_GRAPH_TARGET_PERIOD_MS = 10; /** * Assume that we might miss our scheduled wakeup of the MediaStreamGraph by * this much. */ static const int SCHEDULE_SAFETY_MARGIN_MS = 10; /** * Try have this much audio buffered in streams and queued to the hardware. * The maximum delay to the end of the next control loop * is 2*MEDIA_GRAPH_TARGET_PERIOD_MS + SCHEDULE_SAFETY_MARGIN_MS. * There is no point in buffering more audio than this in a stream at any * given time (until we add processing). * This is not optimal yet. */ static const int AUDIO_TARGET_MS = 2*MEDIA_GRAPH_TARGET_PERIOD_MS + SCHEDULE_SAFETY_MARGIN_MS; class MediaStreamGraphImpl; class AudioCallbackDriver; class OfflineClockDriver; class SystemClockDriver; /** * A driver is responsible for the scheduling of the processing, the thread * management, and give the different clocks to a MediaStreamGraph. This is an * abstract base class. A MediaStreamGraph can be driven by an * OfflineClockDriver, if the graph is offline, or a SystemClockDriver, if the * graph is real time. * A MediaStreamGraph holds an owning reference to its driver. * * The lifetime of drivers is a complicated affair. Here are the different * scenarii that can happen: * * Starting a MediaStreamGraph with an AudioCallbackDriver * - A new thread T is created, from the main thread. * - On this thread T, cubeb is initialized if needed, and a cubeb_stream is * created and started * - The thread T posts a message to the main thread to terminate itself. * - The graph runs off the audio thread * * Starting a MediaStreamGraph with a SystemClockDriver: * - A new thread T is created from the main thread. * - The graph runs off this thread. * * Switching from a SystemClockDriver to an AudioCallbackDriver: * - A new AudioCallabackDriver is created and initialized on the graph thread * - At the end of the MSG iteration, the SystemClockDriver transfers its timing * info and a reference to itself to the AudioCallbackDriver. It then starts * the AudioCallbackDriver. * - When the AudioCallbackDriver starts, it checks if it has been switched from * a SystemClockDriver, and if that is the case, sends a message to the main * thread to shut the SystemClockDriver thread down. * - The graph now runs off an audio callback * * Switching from an AudioCallbackDriver to a SystemClockDriver: * - A new SystemClockDriver is created, and set as mNextDriver. * - At the end of the MSG iteration, the AudioCallbackDriver transfers its * timing info and a reference to itself to the SystemClockDriver. A new * SystemClockDriver is started from the current audio thread. * - When starting, the SystemClockDriver checks if it has been switched from an * AudioCallbackDriver. If yes, it creates a new temporary thread to release * the cubeb_streams. This temporary thread closes the cubeb_stream, and * then dispatches a message to the main thread to be terminated. * - The graph now runs off a normal thread. * * Two drivers cannot run at the same time for the same graph. The thread safety * of the different attributes of drivers, and they access pattern is documented * next to the members themselves. * */ class GraphDriver { public: explicit GraphDriver(MediaStreamGraphImpl* aGraphImpl); NS_INLINE_DECL_THREADSAFE_REFCOUNTING(GraphDriver); /* For real-time graphs, this waits until it's time to process more data. For * offline graphs, this is a no-op. */ virtual void WaitForNextIteration() = 0; /* Wakes up the graph if it is waiting. */ virtual void WakeUp() = 0; virtual void Destroy() {} /* Start the graph, init the driver, start the thread. */ virtual void Start() = 0; /* Stop the graph, shutting down the thread. */ virtual void Stop() = 0; /* Resume after a stop */ virtual void Resume() = 0; /* Revive this driver, as more messages just arrived. */ virtual void Revive() = 0; /* Remove Mixer callbacks when switching */ virtual void RemoveCallback() = 0; /* Shutdown GraphDriver (synchronously) */ void Shutdown(); /* Rate at which the GraphDriver runs, in ms. This can either be user * controlled (because we are using a {System,Offline}ClockDriver, and decide * how often we want to wakeup/how much we want to process per iteration), or * it can be indirectly set by the latency of the audio backend, and the * number of buffers of this audio backend: say we have four buffers, and 40ms * latency, we will get a callback approximately every 10ms. */ virtual uint32_t IterationDuration() = 0; /* Return whether we are switching or not. */ bool Switching(); // Those are simply or setting the associated pointer, but assert that the // lock is held. GraphDriver* NextDriver(); GraphDriver* PreviousDriver(); void SetNextDriver(GraphDriver* aNextDriver); void SetPreviousDriver(GraphDriver* aPreviousDriver); /** * If we are running a real time graph, get the current time stamp to schedule * video frames. This has to be reimplemented by real time drivers. */ virtual TimeStamp GetCurrentTimeStamp() { return mCurrentTimeStamp; } GraphTime IterationEnd() { return mIterationEnd; } virtual AudioCallbackDriver* AsAudioCallbackDriver() { return nullptr; } virtual OfflineClockDriver* AsOfflineClockDriver() { return nullptr; } virtual SystemClockDriver* AsSystemClockDriver() { return nullptr; } /** * Tell the driver it has to stop and return the current time of the graph, so * another driver can start from the right point in time. */ virtual void SwitchAtNextIteration(GraphDriver* aDriver); /** * Set the time for a graph, on a driver. This is used so a new driver just * created can start at the right point in time. */ void SetGraphTime(GraphDriver* aPreviousDriver, GraphTime aLastSwitchNextIterationStart, GraphTime aLastSwitchNextIterationEnd); /** * Call this to indicate that another iteration of the control loop is * required on its regular schedule. The monitor must not be held. * This function has to be idempotent. */ void EnsureNextIteration(); /** * Same thing, but not locked. */ void EnsureNextIterationLocked(); MediaStreamGraphImpl* GraphImpl() { return mGraphImpl; } virtual bool OnThread() = 0; protected: GraphTime StateComputedTime() const; // Time of the start of this graph iteration. This must be accessed while // having the monitor. GraphTime mIterationStart; // Time of the end of this graph iteration. This must be accessed while having // the monitor. GraphTime mIterationEnd; // The MediaStreamGraphImpl associated with this driver. const RefPtr<MediaStreamGraphImpl> mGraphImpl; // This enum specifies the wait state of the driver. enum WaitState { // RunThread() is running normally WAITSTATE_RUNNING, // RunThread() is paused waiting for its next iteration, which will // happen soon WAITSTATE_WAITING_FOR_NEXT_ITERATION, // RunThread() is paused indefinitely waiting for something to change WAITSTATE_WAITING_INDEFINITELY, // Something has signaled RunThread() to wake up immediately, // but it hasn't done so yet WAITSTATE_WAKING_UP }; // This must be access with the monitor. WaitState mWaitState; // This is used on the main thread (during initialization), and the graph // thread. No monitor needed because we know the graph thread does not run // during the initialization. TimeStamp mCurrentTimeStamp; // This is non-null only when this driver has recently switched from an other // driver, and has not cleaned it up yet (for example because the audio stream // is currently calling the callback during initialization). // // This is written to when changing driver, from the previous driver's thread, // or a thread created for the occasion. This is read each time we need to // check whether we're changing driver (in Switching()), from the graph // thread. // This must be accessed using the {Set,Get}PreviousDriver methods. RefPtr<GraphDriver> mPreviousDriver; // This is non-null only when this driver is going to switch to an other // driver at the end of this iteration. // This must be accessed using the {Set,Get}NextDriver methods. RefPtr<GraphDriver> mNextDriver; virtual ~GraphDriver() { } }; class MediaStreamGraphInitThreadRunnable; /** * This class is a driver that manages its own thread. */ class ThreadedDriver : public GraphDriver { public: explicit ThreadedDriver(MediaStreamGraphImpl* aGraphImpl); virtual ~ThreadedDriver(); void Start() override; void Stop() override; void Resume() override; void Revive() override; void RemoveCallback() override; /** * Runs main control loop on the graph thread. Normally a single invocation * of this runs for the entire lifetime of the graph thread. */ void RunThread(); friend class MediaStreamGraphInitThreadRunnable; uint32_t IterationDuration() override { return MEDIA_GRAPH_TARGET_PERIOD_MS; } bool OnThread() override { return !mThread || NS_GetCurrentThread() == mThread; } /* When the graph wakes up to do an iteration, implementations return the * range of time that will be processed. This is called only once per * iteration; it may determine the interval from state in a previous * call. */ virtual MediaTime GetIntervalForIteration() = 0; protected: nsCOMPtr<nsIThread> mThread; }; /** * A SystemClockDriver drives a MediaStreamGraph using a system clock, and waits * using a monitor, between each iteration. */ class SystemClockDriver : public ThreadedDriver { public: explicit SystemClockDriver(MediaStreamGraphImpl* aGraphImpl); virtual ~SystemClockDriver(); MediaTime GetIntervalForIteration() override; void WaitForNextIteration() override; void WakeUp() override; void MarkAsFallback(); bool IsFallback(); SystemClockDriver* AsSystemClockDriver() override { return this; } private: // Those are only modified (after initialization) on the graph thread. The // graph thread does not run during the initialization. TimeStamp mInitialTimeStamp; TimeStamp mLastTimeStamp; // This is true if this SystemClockDriver runs the graph because we could not // open an audio stream. bool mIsFallback; }; /** * An OfflineClockDriver runs the graph as fast as possible, without waiting * between iteration. */ class OfflineClockDriver : public ThreadedDriver { public: OfflineClockDriver(MediaStreamGraphImpl* aGraphImpl, GraphTime aSlice); virtual ~OfflineClockDriver(); MediaTime GetIntervalForIteration() override; void WaitForNextIteration() override; void WakeUp() override; TimeStamp GetCurrentTimeStamp() override; OfflineClockDriver* AsOfflineClockDriver() override { return this; } private: // Time, in GraphTime, for each iteration GraphTime mSlice; }; struct StreamAndPromiseForOperation { StreamAndPromiseForOperation(MediaStream* aStream, void* aPromise, dom::AudioContextOperation aOperation); RefPtr<MediaStream> mStream; void* mPromise; dom::AudioContextOperation mOperation; }; enum AsyncCubebOperation { INIT, SHUTDOWN }; /** * This is a graph driver that is based on callback functions called by the * audio api. This ensures minimal audio latency, because it means there is no * buffering happening: the audio is generated inside the callback. * * This design is less flexible than running our own thread: * - We have no control over the thread: * - It cannot block, and it has to run for a shorter amount of time than the * buffer it is going to fill, or an under-run is going to occur (short burst * of silence in the final audio output). * - We can't know for sure when the callback function is going to be called * (although we compute an estimation so we can schedule video frames) * - Creating and shutting the thread down is a blocking operation, that can * take _seconds_ in some cases (because IPC has to be set up, and * sometimes hardware components are involved and need to be warmed up) * - We have no control on how much audio we generate, we have to return exactly * the number of frames asked for by the callback. Since for the Web Audio * API, we have to do block processing at 128 frames per block, we need to * keep a little spill buffer to store the extra frames. */ class AudioCallbackDriver : public GraphDriver, public MixerCallbackReceiver { public: explicit AudioCallbackDriver(MediaStreamGraphImpl* aGraphImpl); virtual ~AudioCallbackDriver(); void Destroy() override; void Start() override; void Stop() override; void Resume() override; void Revive() override; void RemoveCallback() override; void WaitForNextIteration() override; void WakeUp() override; /* Static wrapper function cubeb calls back. */ static long DataCallback_s(cubeb_stream * aStream, void * aUser, const void * aInputBuffer, void * aOutputBuffer, long aFrames); static void StateCallback_s(cubeb_stream* aStream, void * aUser, cubeb_state aState); static void DeviceChangedCallback_s(void * aUser); /* This function is called by the underlying audio backend when a refill is * needed. This is what drives the whole graph when it is used to output * audio. If the return value is exactly aFrames, this function will get * called again. If it is less than aFrames, the stream will go in draining * mode, and this function will not be called again. */ long DataCallback(const AudioDataValue* aInputBuffer, AudioDataValue* aOutputBuffer, long aFrames); /* This function is called by the underlying audio backend, but is only used * for informational purposes at the moment. */ void StateCallback(cubeb_state aState); /* This is an approximation of the number of millisecond there are between two * iterations of the graph. */ uint32_t IterationDuration() override; /* This function gets called when the graph has produced the audio frames for * this iteration. */ void MixerCallback(AudioDataValue* aMixedBuffer, AudioSampleFormat aFormat, uint32_t aChannels, uint32_t aFrames, uint32_t aSampleRate) override; // These are invoked on the MSG thread (we don't call this if not LIFECYCLE_RUNNING) virtual void SetInputListener(AudioDataListener *aListener) { MOZ_ASSERT(OnThread()); mAudioInput = aListener; } // XXX do we need the param? probably no virtual void RemoveInputListener(AudioDataListener *aListener) { MOZ_ASSERT(OnThread()); mAudioInput = nullptr; } AudioCallbackDriver* AsAudioCallbackDriver() override { return this; } /* Enqueue a promise that is going to be resolved when a specific operation * occurs on the cubeb stream. */ void EnqueueStreamAndPromiseForOperation(MediaStream* aStream, void* aPromise, dom::AudioContextOperation aOperation); /** * Whether the audio callback is processing. This is for asserting only. */ bool InCallback(); bool OnThread() override { return !mStarted || InCallback(); } /* Whether the underlying cubeb stream has been started. See comment for * mStarted for details. */ bool IsStarted(); /* Tell the driver whether this process is using a microphone or not. This is * thread safe. */ void SetMicrophoneActive(bool aActive); void CompleteAudioContextOperations(AsyncCubebOperation aOperation); private: /** * On certain MacBookPro, the microphone is located near the left speaker. * We need to pan the sound output to the right speaker if we are using the * mic and the built-in speaker, or we will have terrible echo. */ void PanOutputIfNeeded(bool aMicrophoneActive); /** * This is called when the output device used by the cubeb stream changes. */ void DeviceChangedCallback(); /* Start the cubeb stream */ void StartStream(); friend class AsyncCubebTask; void Init(); /* MediaStreamGraphs are always down/up mixed to stereo for now. */ static const uint32_t ChannelCount = 2; /* The size of this buffer comes from the fact that some audio backends can * call back with a number of frames lower than one block (128 frames), so we * need to keep at most two block in the SpillBuffer, because we always round * up to block boundaries during an iteration. * This is only ever accessed on the audio callback thread. */ SpillBuffer<AudioDataValue, WEBAUDIO_BLOCK_SIZE * 2, ChannelCount> mScratchBuffer; /* Wrapper to ensure we write exactly the number of frames we need in the * audio buffer cubeb passes us. This is only ever accessed on the audio * callback thread. */ AudioCallbackBufferWrapper<AudioDataValue, ChannelCount> mBuffer; /* cubeb stream for this graph. This is guaranteed to be non-null after Init() * has been called, and is synchronized internaly. */ nsAutoRef<cubeb_stream> mAudioStream; /* The sample rate for the aforementionned cubeb stream. This is set on * initialization and can be read safely afterwards. */ uint32_t mSampleRate; /* The number of input channels from cubeb. Should be set before opening cubeb * and then be static. */ uint32_t mInputChannels; /* Approximation of the time between two callbacks. This is used to schedule * video frames. This is in milliseconds. Only even used (after * inizatialization) on the audio callback thread. */ uint32_t mIterationDurationMS; /* cubeb_stream_init calls the audio callback to prefill the buffers. The * previous driver has to be kept alive until the audio stream has been * started, because it is responsible to call cubeb_stream_start, so we delay * the cleanup of the previous driver until it has started the audio stream. * Otherwise, there is a race where we kill the previous driver thread * between cubeb_stream_init and cubeb_stream_start, * and callbacks after the prefill never get called. * This is written on the previous driver's thread (if switching) or main * thread (if this driver is the first one). * This is read on previous driver's thread (during callbacks from * cubeb_stream_init) and the audio thread (when switching away from this * driver back to a SystemClockDriver). * This is synchronized by the Graph's monitor. * */ bool mStarted; /* Listener for mic input, if any. */ RefPtr<AudioDataListener> mAudioInput; struct AutoInCallback { explicit AutoInCallback(AudioCallbackDriver* aDriver); ~AutoInCallback(); AudioCallbackDriver* mDriver; }; /* Thread for off-main-thread initialization and * shutdown of the audio stream. */ nsCOMPtr<nsIThread> mInitShutdownThread; /* This must be accessed with the graph monitor held. */ AutoTArray<StreamAndPromiseForOperation, 1> mPromisesForOperation; /* This is set during initialization, and can be read safely afterwards. */ dom::AudioChannel mAudioChannel; /* Used to queue us to add the mixer callback on first run. */ bool mAddedMixer; /* This is atomic and is set by the audio callback thread. It can be read by * any thread safely. */ Atomic<bool> mInCallback; /** * True if microphone is being used by this process. This is synchronized by * the graph's monitor. */ bool mMicrophoneActive; /* Indication of whether a fallback SystemClockDriver should be started if * StateCallback() receives an error. No mutex need be held during access. * The transition to true happens before cubeb_stream_start() is called. * After transitioning to false on the last DataCallback(), the stream is * not accessed from another thread until the graph thread either signals * main thread cleanup or dispatches an event to switch to another * driver. */ bool mShouldFallbackIfError; /* True if this driver was created from a driver created because of a previous * AudioCallbackDriver failure. */ bool mFromFallback; }; class AsyncCubebTask : public Runnable { public: AsyncCubebTask(AudioCallbackDriver* aDriver, AsyncCubebOperation aOperation); nsresult Dispatch(uint32_t aFlags = NS_DISPATCH_NORMAL) { nsresult rv = EnsureThread(); if (!NS_FAILED(rv)) { rv = sThreadPool->Dispatch(this, aFlags); } return rv; } protected: virtual ~AsyncCubebTask(); private: static nsresult EnsureThread(); NS_IMETHOD Run() override final; static StaticRefPtr<nsIThreadPool> sThreadPool; RefPtr<AudioCallbackDriver> mDriver; AsyncCubebOperation mOperation; RefPtr<MediaStreamGraphImpl> mShutdownGrip; }; } // namespace mozilla #endif // GRAPHDRIVER_H_