gecko-dev/dom/media/GraphDriver.h

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/* -*- 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 that owns this driver. This has a lifetime longer
// than the driver, and will never be null. Hence, it can be accesed without
// monitor.
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 || mThread->EventTarget()->IsOnCurrentThread(); }
/* 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 */
bool StartStream();
friend class AsyncCubebTask;
bool 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. */
Atomic<bool> mMicrophoneActive;
/* 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_