tenfourfox/dom/media/GraphDriver.cpp

/* -*- 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/. */

#include <MediaStreamGraphImpl.h>
#include "mozilla/dom/AudioContext.h"
#include "CubebUtils.h"

#ifdef XP_MACOSX
#include <sys/sysctl.h>
#endif

extern mozilla::LazyLogModule gMediaStreamGraphLog;
#define STREAM_LOG(type, msg) MOZ_LOG(gMediaStreamGraphLog, type, msg)

// We don't use NSPR log here because we want this interleaved with adb logcat
// on Android/B2G
// #define ENABLE_LIFECYCLE_LOG
#ifdef ENABLE_LIFECYCLE_LOG
#ifdef ANDROID
#include "android/log.h"
#define LIFECYCLE_LOG(...)  __android_log_print(ANDROID_LOG_INFO, "Gecko - MSG" , __VA_ARGS__); printf(__VA_ARGS__);printf("\n");
#else
#define LIFECYCLE_LOG(...) printf(__VA_ARGS__);printf("\n");
#endif
#else
#define LIFECYCLE_LOG(...)
#endif

namespace mozilla {

struct AutoProfilerUnregisterThread
{
  // The empty ctor is used to silence a pre-4.8.0 GCC unused variable warning.
  AutoProfilerUnregisterThread()
  {
  }

  ~AutoProfilerUnregisterThread()
  {
    profiler_unregister_thread();
  }
};

GraphDriver::GraphDriver(MediaStreamGraphImpl* aGraphImpl)
  : mIterationStart(0),
    mIterationEnd(0),
    mGraphImpl(aGraphImpl),
    mWaitState(WAITSTATE_RUNNING),
    mCurrentTimeStamp(TimeStamp::Now()),
    mPreviousDriver(nullptr),
    mNextDriver(nullptr)
{ }

void GraphDriver::SetGraphTime(GraphDriver* aPreviousDriver,
                               GraphTime aLastSwitchNextIterationStart,
                               GraphTime aLastSwitchNextIterationEnd)
{
  // We set mIterationEnd here, because the first thing a driver do when it
  // does an iteration is to update graph times, so we are in fact setting
  // mIterationStart of the next iteration by setting the end of the previous
  // iteration.
  mIterationStart = aLastSwitchNextIterationStart;
  mIterationEnd = aLastSwitchNextIterationEnd;

  STREAM_LOG(LogLevel::Debug, ("Setting previous driver: %p (%s)", aPreviousDriver, aPreviousDriver->AsAudioCallbackDriver() ? "AudioCallbackDriver" : "SystemClockDriver"));
  MOZ_ASSERT(!mPreviousDriver);
  mPreviousDriver = aPreviousDriver;
}

void GraphDriver::SwitchAtNextIteration(GraphDriver* aNextDriver)
{
  // This is the situation where `mPreviousDriver` is an AudioCallbackDriver
  // that is switching device, and the graph has found the current driver is not
  // an AudioCallbackDriver, but tries to switch to a _new_ AudioCallbackDriver
  // because it found audio has to be output. In this case, simply ignore the
  // request to switch, since we know we will switch back to the old
  // AudioCallbackDriver when it has recovered from the device switching.
  if (aNextDriver->AsAudioCallbackDriver() &&
      mPreviousDriver &&
      mPreviousDriver->AsAudioCallbackDriver()->IsSwitchingDevice() &&
      mPreviousDriver != aNextDriver) {
    return;
  }
  LIFECYCLE_LOG("Switching to new driver: %p (%s)",
      aNextDriver, aNextDriver->AsAudioCallbackDriver() ?
      "AudioCallbackDriver" : "SystemClockDriver");
  mNextDriver = aNextDriver;
}

void GraphDriver::EnsureImmediateWakeUpLocked()
{
  mGraphImpl->GetMonitor().AssertCurrentThreadOwns();
  mWaitState = WAITSTATE_WAKING_UP;
  mGraphImpl->mGraphDriverAsleep = false; // atomic
  mGraphImpl->GetMonitor().Notify();
}

GraphTime
GraphDriver::StateComputedTime() const
{
  return mGraphImpl->mStateComputedTime;
}

void GraphDriver::EnsureNextIteration()
{
  mGraphImpl->EnsureNextIteration();
}

class MediaStreamGraphShutdownThreadRunnable : public nsRunnable {
public:
  explicit MediaStreamGraphShutdownThreadRunnable(GraphDriver* aDriver)
    : mDriver(aDriver)
  {
  }
  NS_IMETHOD Run()
  {
    MOZ_ASSERT(NS_IsMainThread());

    LIFECYCLE_LOG("MediaStreamGraphShutdownThreadRunnable for graph %p",
        mDriver->GraphImpl());
    // We can't release an audio driver on the main thread, because it can be
    // blocking.
    if (mDriver->AsAudioCallbackDriver()) {
      LIFECYCLE_LOG("Releasing audio driver off main thread.");
      RefPtr<AsyncCubebTask> releaseEvent =
        new AsyncCubebTask(mDriver->AsAudioCallbackDriver(),
                           AsyncCubebOperation::SHUTDOWN);
      mDriver = nullptr;
      releaseEvent->Dispatch();
    } else {
      LIFECYCLE_LOG("Dropping driver reference for SystemClockDriver.");
      mDriver = nullptr;
    }
    return NS_OK;
  }
private:
  RefPtr<GraphDriver> mDriver;
};

void GraphDriver::Shutdown()
{
  if (AsAudioCallbackDriver()) {
    LIFECYCLE_LOG("Releasing audio driver off main thread (GraphDriver::Shutdown).\n");
    RefPtr<AsyncCubebTask> releaseEvent =
      new AsyncCubebTask(AsAudioCallbackDriver(), AsyncCubebOperation::SHUTDOWN);
    releaseEvent->Dispatch();
  } else {
    Stop();
  }
}

ThreadedDriver::ThreadedDriver(MediaStreamGraphImpl* aGraphImpl)
  : GraphDriver(aGraphImpl)
{ }

ThreadedDriver::~ThreadedDriver()
{
  if (mThread) {
    mThread->Shutdown();
  }
}
class MediaStreamGraphInitThreadRunnable : public nsRunnable {
public:
  explicit MediaStreamGraphInitThreadRunnable(ThreadedDriver* aDriver)
    : mDriver(aDriver)
  {
  }
  NS_IMETHOD Run()
  {
    char aLocal;
    STREAM_LOG(LogLevel::Debug, ("Starting system thread"));
    profiler_register_thread("MediaStreamGraph", &aLocal);
    LIFECYCLE_LOG("Starting a new system driver for graph %p\n",
                  mDriver->mGraphImpl.get());
    if (mDriver->mPreviousDriver) {
      LIFECYCLE_LOG("%p releasing an AudioCallbackDriver(%p), for graph %p\n",
                    mDriver,
                    mDriver->mPreviousDriver.get(),
                    mDriver->GraphImpl());
      MOZ_ASSERT(!mDriver->AsAudioCallbackDriver());
      // Stop and release the previous driver off-main-thread, but only if we're
      // not in the situation where we've fallen back to a system clock driver
      // because the osx audio stack is currently switching output device.
      if (!mDriver->mPreviousDriver->AsAudioCallbackDriver()->IsSwitchingDevice()) {
        RefPtr<AsyncCubebTask> releaseEvent =
          new AsyncCubebTask(mDriver->mPreviousDriver->AsAudioCallbackDriver(), AsyncCubebOperation::SHUTDOWN);
        mDriver->mPreviousDriver = nullptr;
        releaseEvent->Dispatch();
      }
    } else {
      MonitorAutoLock mon(mDriver->mGraphImpl->GetMonitor());
      MOZ_ASSERT(mDriver->mGraphImpl->MessagesQueued(), "Don't start a graph without messages queued.");
      mDriver->mGraphImpl->SwapMessageQueues();
    }
    mDriver->RunThread();
    return NS_OK;
  }
private:
  RefPtr<ThreadedDriver> mDriver;
};

void
ThreadedDriver::Start()
{
  LIFECYCLE_LOG("Starting thread for a SystemClockDriver  %p\n", mGraphImpl.get());
  nsCOMPtr<nsIRunnable> event = new MediaStreamGraphInitThreadRunnable(this);
  // Note: mThread may be null during event->Run() if we pass to NewNamedThread!  See AudioInitTask
  nsresult rv = NS_NewNamedThread("MediaStreamGrph", getter_AddRefs(mThread));
  if (NS_SUCCEEDED(rv)) {
    mThread->Dispatch(event, NS_DISPATCH_NORMAL);
  }
}

void
ThreadedDriver::Resume()
{
  Start();
}

void
ThreadedDriver::Revive()
{
  // Note: only called on MainThread, without monitor
  // We know were weren't in a running state
  STREAM_LOG(LogLevel::Debug, ("AudioCallbackDriver reviving."));
  // If we were switching, switch now. Otherwise, tell thread to run the main
  // loop again.
  MonitorAutoLock mon(mGraphImpl->GetMonitor());
  if (mNextDriver) {
    mNextDriver->SetGraphTime(this, mIterationStart, mIterationEnd);
    mGraphImpl->SetCurrentDriver(mNextDriver);
    mNextDriver->Start();
  } else {
    nsCOMPtr<nsIRunnable> event = new MediaStreamGraphInitThreadRunnable(this);
    mThread->Dispatch(event, NS_DISPATCH_NORMAL);
  }
}

void
ThreadedDriver::Stop()
{
  NS_ASSERTION(NS_IsMainThread(), "Must be called on main thread");
  // mGraph's thread is not running so it's OK to do whatever here
  STREAM_LOG(LogLevel::Debug, ("Stopping threads for MediaStreamGraph %p", this));

  if (mThread) {
    mThread->Shutdown();
    mThread = nullptr;
  }
}

SystemClockDriver::SystemClockDriver(MediaStreamGraphImpl* aGraphImpl)
  : ThreadedDriver(aGraphImpl),
    mInitialTimeStamp(TimeStamp::Now()),
    mLastTimeStamp(TimeStamp::Now())
{}

SystemClockDriver::~SystemClockDriver()
{ }

void
ThreadedDriver::RunThread()
{
  AutoProfilerUnregisterThread autoUnregister;

  bool stillProcessing = true;
  while (stillProcessing) {
    mIterationStart = IterationEnd();
    mIterationEnd += GetIntervalForIteration();

    GraphTime stateComputedTime = StateComputedTime();
    if (stateComputedTime < mIterationEnd) {
      STREAM_LOG(LogLevel::Warning, ("Media graph global underrun detected"));
      mIterationEnd = stateComputedTime;
    }

    if (mIterationStart >= mIterationEnd) {
      NS_ASSERTION(mIterationStart == mIterationEnd ,
                   "Time can't go backwards!");
      // This could happen due to low clock resolution, maybe?
      STREAM_LOG(LogLevel::Debug, ("Time did not advance"));
    }

    GraphTime nextStateComputedTime =
      mGraphImpl->RoundUpToNextAudioBlock(
        mIterationEnd + mGraphImpl->MillisecondsToMediaTime(AUDIO_TARGET_MS));
    if (nextStateComputedTime < stateComputedTime) {
      // A previous driver may have been processing further ahead of
      // iterationEnd.
      STREAM_LOG(LogLevel::Warning,
                 ("Prevent state from going backwards. interval[%ld; %ld] state[%ld; %ld]",
                  (long)mIterationStart, (long)mIterationEnd,
                  (long)stateComputedTime, (long)nextStateComputedTime));
      nextStateComputedTime = stateComputedTime;
    }
    STREAM_LOG(LogLevel::Debug,
               ("interval[%ld; %ld] state[%ld; %ld]",
               (long)mIterationStart, (long)mIterationEnd,
               (long)stateComputedTime, (long)nextStateComputedTime));

    stillProcessing = mGraphImpl->OneIteration(nextStateComputedTime);

    if (mNextDriver && stillProcessing) {
      STREAM_LOG(LogLevel::Debug, ("Switching to AudioCallbackDriver"));
      mNextDriver->SetGraphTime(this, mIterationStart, mIterationEnd);
      mGraphImpl->SetCurrentDriver(mNextDriver);
      mNextDriver->Start();
      return;
    }
  }
}

MediaTime
SystemClockDriver::GetIntervalForIteration()
{
  TimeStamp now = TimeStamp::Now();
  MediaTime interval =
    mGraphImpl->SecondsToMediaTime((now - mCurrentTimeStamp).ToSeconds());
  mCurrentTimeStamp = now;

  MOZ_LOG(gMediaStreamGraphLog, LogLevel::Verbose,
          ("Updating current time to %f (real %f, StateComputedTime() %f)",
           mGraphImpl->MediaTimeToSeconds(IterationEnd() + interval),
           (now - mInitialTimeStamp).ToSeconds(),
           mGraphImpl->MediaTimeToSeconds(StateComputedTime())));

  return interval;
}

TimeStamp
OfflineClockDriver::GetCurrentTimeStamp()
{
  MOZ_CRASH("This driver does not support getting the current timestamp.");
  return TimeStamp();
}

void
SystemClockDriver::WaitForNextIteration()
{
  mGraphImpl->GetMonitor().AssertCurrentThreadOwns();

  PRIntervalTime timeout = PR_INTERVAL_NO_TIMEOUT;
  TimeStamp now = TimeStamp::Now();
  if (mGraphImpl->mNeedAnotherIteration) {
    int64_t timeoutMS = MEDIA_GRAPH_TARGET_PERIOD_MS -
      int64_t((now - mCurrentTimeStamp).ToMilliseconds());
    // Make sure timeoutMS doesn't overflow 32 bits by waking up at
    // least once a minute, if we need to wake up at all
    timeoutMS = std::max<int64_t>(0, std::min<int64_t>(timeoutMS, 60*1000));
    timeout = PR_MillisecondsToInterval(uint32_t(timeoutMS));
    STREAM_LOG(LogLevel::Verbose, ("Waiting for next iteration; at %f, timeout=%f", (now - mInitialTimeStamp).ToSeconds(), timeoutMS/1000.0));
    if (mWaitState == WAITSTATE_WAITING_INDEFINITELY) {
      mGraphImpl->mGraphDriverAsleep = false; // atomic
    }
    mWaitState = WAITSTATE_WAITING_FOR_NEXT_ITERATION;
  } else {
    mGraphImpl->mGraphDriverAsleep = true; // atomic
    mWaitState = WAITSTATE_WAITING_INDEFINITELY;
  }
  if (timeout > 0) {
    mGraphImpl->GetMonitor().Wait(timeout);
    STREAM_LOG(LogLevel::Verbose, ("Resuming after timeout; at %f, elapsed=%f",
          (TimeStamp::Now() - mInitialTimeStamp).ToSeconds(),
          (TimeStamp::Now() - now).ToSeconds()));
  }

  if (mWaitState == WAITSTATE_WAITING_INDEFINITELY) {
    mGraphImpl->mGraphDriverAsleep = false; // atomic
  }
  mWaitState = WAITSTATE_RUNNING;
  mGraphImpl->mNeedAnotherIteration = false;
}

void
SystemClockDriver::WakeUp()
{
  mGraphImpl->GetMonitor().AssertCurrentThreadOwns();
  mWaitState = WAITSTATE_WAKING_UP;
  mGraphImpl->mGraphDriverAsleep = false; // atomic
  mGraphImpl->GetMonitor().Notify();
}

OfflineClockDriver::OfflineClockDriver(MediaStreamGraphImpl* aGraphImpl, GraphTime aSlice)
  : ThreadedDriver(aGraphImpl),
    mSlice(aSlice)
{

}

class MediaStreamGraphShutdownThreadRunnable2 : public nsRunnable {
public:
  explicit MediaStreamGraphShutdownThreadRunnable2(nsIThread* aThread)
    : mThread(aThread)
  {
  }
  NS_IMETHOD Run()
  {
    MOZ_ASSERT(NS_IsMainThread());
    MOZ_ASSERT(mThread);

    mThread->Shutdown();
    mThread = nullptr;
    return NS_OK;
  }
private:
  nsCOMPtr<nsIThread> mThread;
};

OfflineClockDriver::~OfflineClockDriver()
{
  // transfer the ownership of mThread to the event
  // XXX should use .forget()/etc
  if (mThread) {
    nsCOMPtr<nsIRunnable> event = new MediaStreamGraphShutdownThreadRunnable2(mThread);
    mThread = nullptr;
    NS_DispatchToMainThread(event);
  }
}

MediaTime
OfflineClockDriver::GetIntervalForIteration()
{
  return mGraphImpl->MillisecondsToMediaTime(mSlice);
}

void
OfflineClockDriver::WaitForNextIteration()
{
  // No op: we want to go as fast as possible when we are offline
}

void
OfflineClockDriver::WakeUp()
{
  MOZ_ASSERT(false, "An offline graph should not have to wake up.");
}

AsyncCubebTask::AsyncCubebTask(AudioCallbackDriver* aDriver, AsyncCubebOperation aOperation)
  : mDriver(aDriver),
    mOperation(aOperation),
    mShutdownGrip(aDriver->GraphImpl())
{
  NS_WARN_IF_FALSE(mDriver->mAudioStream || aOperation == INIT, "No audio stream !");
}

AsyncCubebTask::~AsyncCubebTask()
{
}

NS_IMETHODIMP
AsyncCubebTask::Run()
{
  MOZ_ASSERT(mThread);
  if (NS_IsMainThread()) {
    mThread->Shutdown(); // can't shutdown from the thread itself, darn
    // don't null out mThread!
    // See bug 999104.  we must hold a ref to the thread across Dispatch()
    // since the internal mthread ref could be released while processing
    // the Dispatch(), and Dispatch/PutEvent itself doesn't hold a ref; it
    // assumes the caller does.
    return NS_OK;
  }

  MOZ_ASSERT(mDriver);

  switch(mOperation) {
    case AsyncCubebOperation::INIT: {
      LIFECYCLE_LOG("AsyncCubebOperation::INIT\n");
      mDriver->Init();
      mDriver->CompleteAudioContextOperations(mOperation);
      break;
    }
    case AsyncCubebOperation::SHUTDOWN: {
      LIFECYCLE_LOG("AsyncCubebOperation::SHUTDOWN\n");
      mDriver->Stop();

      mDriver->CompleteAudioContextOperations(mOperation);

      mDriver = nullptr;
      mShutdownGrip = nullptr;
      break;
    }
    default:
      MOZ_CRASH("Operation not implemented.");
  }

  // and now kill this thread
  NS_DispatchToMainThread(this);

  return NS_OK;
}

StreamAndPromiseForOperation::StreamAndPromiseForOperation(MediaStream* aStream,
                                          void* aPromise,
                                          dom::AudioContextOperation aOperation)
  : mStream(aStream)
  , mPromise(aPromise)
  , mOperation(aOperation)
{
  // MOZ_ASSERT(aPromise);
}

AudioCallbackDriver::AudioCallbackDriver(MediaStreamGraphImpl* aGraphImpl)
  : GraphDriver(aGraphImpl)
  , mSampleRate(0)
  , mIterationDurationMS(MEDIA_GRAPH_TARGET_PERIOD_MS)
  , mStarted(false)
  , mAudioChannel(aGraphImpl->AudioChannel())
  , mInCallback(false)
  , mPauseRequested(false)
  , mMicrophoneActive(false)
#ifdef XP_MACOSX
  , mCallbackReceivedWhileSwitching(0)
#endif
{
  STREAM_LOG(LogLevel::Debug, ("AudioCallbackDriver ctor for graph %p", aGraphImpl));
}

AudioCallbackDriver::~AudioCallbackDriver()
{
  MOZ_ASSERT(mPromisesForOperation.IsEmpty());
}

void
AudioCallbackDriver::Init()
{
  cubeb_stream_params params;
  uint32_t latency;

  MOZ_ASSERT(!NS_IsMainThread(),
      "This is blocking and should never run on the main thread.");

  mSampleRate = params.rate = CubebUtils::PreferredSampleRate();

#if defined(__ANDROID__)
#if defined(MOZ_B2G)
  params.stream_type = CubebUtils::ConvertChannelToCubebType(mAudioChannel);
#else
  params.stream_type = CUBEB_STREAM_TYPE_MUSIC;
#endif
  if (params.stream_type == CUBEB_STREAM_TYPE_MAX) {
    NS_WARNING("Bad stream type");
    return;
  }
#else
  (void)mAudioChannel;
#endif

  params.channels = mGraphImpl->AudioChannelCount();
  if (AUDIO_OUTPUT_FORMAT == AUDIO_FORMAT_S16) {
    params.format = CUBEB_SAMPLE_S16NE;
  } else {
    params.format = CUBEB_SAMPLE_FLOAT32NE;
  }

  if (cubeb_get_min_latency(CubebUtils::GetCubebContext(), params, &latency) != CUBEB_OK) {
    NS_WARNING("Could not get minimal latency from cubeb.");
  }

  cubeb_stream* stream;
  if (cubeb_stream_init(CubebUtils::GetCubebContext(), &stream,
                        "AudioCallbackDriver", params, latency,
                        DataCallback_s, StateCallback_s, this) == CUBEB_OK) {
    mAudioStream.own(stream);
  } else {
    NS_WARNING("Could not create a cubeb stream for MediaStreamGraph, falling back to a SystemClockDriver");
    // Fall back to a driver using a normal thread. If needed,
    // the graph will try to re-open an audio stream later.
    mNextDriver = new SystemClockDriver(GraphImpl());
    mNextDriver->SetGraphTime(this, mIterationStart, mIterationEnd);
    // We're not using SwitchAtNextIteration here, because there
    // won't be a next iteration if we don't restart things manually:
    // the audio stream just signaled that it's in error state.
    mGraphImpl->SetCurrentDriver(mNextDriver);
    DebugOnly<bool> found = mGraphImpl->RemoveMixerCallback(this);
    NS_WARN_IF_FALSE(!found, "Mixer callback not added when switching?");
    mNextDriver->Start();
    return;
  }

  cubeb_stream_register_device_changed_callback(mAudioStream,
                                                AudioCallbackDriver::DeviceChangedCallback_s);

  StartStream();

  STREAM_LOG(LogLevel::Debug, ("AudioCallbackDriver started."));
}


void
AudioCallbackDriver::Destroy()
{
  STREAM_LOG(LogLevel::Debug, ("AudioCallbackDriver destroyed."));
  mAudioStream.reset();
}

void
AudioCallbackDriver::Resume()
{
  STREAM_LOG(LogLevel::Debug, ("Resuming audio threads for MediaStreamGraph %p", mGraphImpl.get()));
  if (cubeb_stream_start(mAudioStream) != CUBEB_OK) {
    NS_WARNING("Could not start cubeb stream for MSG.");
  }
}

void
AudioCallbackDriver::Start()
{
  // If this is running on the main thread, we can't open the stream directly,
  // because it is a blocking operation.
  if (NS_IsMainThread()) {
    STREAM_LOG(LogLevel::Debug, ("Starting audio threads for MediaStreamGraph %p from a new thread.", mGraphImpl.get()));
    RefPtr<AsyncCubebTask> initEvent =
      new AsyncCubebTask(this, AsyncCubebOperation::INIT);
    initEvent->Dispatch();
  } else {
    STREAM_LOG(LogLevel::Debug, ("Starting audio threads for MediaStreamGraph %p from the previous driver's thread", mGraphImpl.get()));
    Init();

    // Check if we need to resolve promises because the driver just got switched
    // because of a resuming AudioContext
    if (!mPromisesForOperation.IsEmpty()) {
      CompleteAudioContextOperations(AsyncCubebOperation::INIT);
    }

    if (mPreviousDriver) {
      nsCOMPtr<nsIRunnable> event =
        new MediaStreamGraphShutdownThreadRunnable(mPreviousDriver);
      mPreviousDriver = nullptr;
      NS_DispatchToMainThread(event);
    }
  }
}

void
AudioCallbackDriver::StartStream()
{
  if (cubeb_stream_start(mAudioStream) != CUBEB_OK) {
    MOZ_CRASH("Could not start cubeb stream for MSG.");
  }

  {
    MonitorAutoLock mon(mGraphImpl->GetMonitor());
    mStarted = true;
    mWaitState = WAITSTATE_RUNNING;
  }
}

void
AudioCallbackDriver::Stop()
{
  if (cubeb_stream_stop(mAudioStream) != CUBEB_OK) {
    NS_WARNING("Could not stop cubeb stream for MSG.");
  }
}

void
AudioCallbackDriver::Revive()
{
  // Note: only called on MainThread, without monitor
  // We know were weren't in a running state
  STREAM_LOG(LogLevel::Debug, ("AudioCallbackDriver reviving."));
  // If we were switching, switch now. Otherwise, start the audio thread again.
  MonitorAutoLock mon(mGraphImpl->GetMonitor());
  if (mNextDriver) {
    mNextDriver->SetGraphTime(this, mIterationStart, mIterationEnd);
    mGraphImpl->SetCurrentDriver(mNextDriver);
    mNextDriver->Start();
  } else {
    STREAM_LOG(LogLevel::Debug, ("Starting audio threads for MediaStreamGraph %p from a new thread.", mGraphImpl.get()));
    RefPtr<AsyncCubebTask> initEvent =
      new AsyncCubebTask(this, AsyncCubebOperation::INIT);
    initEvent->Dispatch();
  }
}

void AudioCallbackDriver::WaitForNextIteration()
{
}

void
AudioCallbackDriver::WakeUp()
{
  mGraphImpl->GetMonitor().AssertCurrentThreadOwns();
  mGraphImpl->GetMonitor().Notify();
}

/* static */ long
AudioCallbackDriver::DataCallback_s(cubeb_stream* aStream,
                                    void* aUser, void* aBuffer,
                                    long aFrames)
{
  AudioCallbackDriver* driver = reinterpret_cast<AudioCallbackDriver*>(aUser);
  return driver->DataCallback(static_cast<AudioDataValue*>(aBuffer), aFrames);
}

/* static */ void
AudioCallbackDriver::StateCallback_s(cubeb_stream* aStream, void * aUser,
                                     cubeb_state aState)
{
  AudioCallbackDriver* driver = reinterpret_cast<AudioCallbackDriver*>(aUser);
  driver->StateCallback(aState);
}

/* static */ void
AudioCallbackDriver::DeviceChangedCallback_s(void* aUser)
{
  AudioCallbackDriver* driver = reinterpret_cast<AudioCallbackDriver*>(aUser);
  driver->DeviceChangedCallback();
}

bool AudioCallbackDriver::InCallback() {
  return mInCallback;
}

AudioCallbackDriver::AutoInCallback::AutoInCallback(AudioCallbackDriver* aDriver)
  : mDriver(aDriver)
{
  mDriver->mInCallback = true;
}

AudioCallbackDriver::AutoInCallback::~AutoInCallback() {
  mDriver->mInCallback = false;
}

#ifdef XP_MACOSX
bool
AudioCallbackDriver::OSXDeviceSwitchingWorkaround()
{
  MonitorAutoLock mon(GraphImpl()->GetMonitor());
  if (mSelfReference) {
    // Apparently, depending on the osx version, on device switch, the
    // callback is called "some" number of times, and then stops being called,
    // and then gets called again. 10 is to be safe, it's a low-enough number
    // of milliseconds anyways (< 100ms)
    //STREAM_LOG(LogLevel::Debug, ("Callbacks during switch: %d", mCallbackReceivedWhileSwitching+1));
    if (mCallbackReceivedWhileSwitching++ >= 10) {
      STREAM_LOG(LogLevel::Debug, ("Got %d callbacks, switching back to CallbackDriver", mCallbackReceivedWhileSwitching));
      // If we have a self reference, we have fallen back temporarily on a
      // system clock driver, but we just got called back, that means the osx
      // audio backend has switched to the new device.
      // Ask the graph to switch back to the previous AudioCallbackDriver
      // (`this`), and when the graph has effectively switched, we can drop
      // the self reference and unref the SystemClockDriver we fallen back on.
      if (GraphImpl()->CurrentDriver() == this) {
        mSelfReference.Drop(this);
        mNextDriver = nullptr;
      } else {
        GraphImpl()->CurrentDriver()->SwitchAtNextIteration(this);
      }

    }
    return true;
  }

  return false;
}
#endif // XP_MACOSX

long
AudioCallbackDriver::DataCallback(AudioDataValue* aBuffer, long aFrames)
{
  bool stillProcessing;

  if (mPauseRequested) {
    PodZero(aBuffer, aFrames * mGraphImpl->AudioChannelCount());
    return aFrames;
  }

#ifdef XP_MACOSX
  if (OSXDeviceSwitchingWorkaround()) {
    PodZero(aBuffer, aFrames * mGraphImpl->AudioChannelCount());
    return aFrames;
  }
#endif

#ifdef DEBUG
  // DebugOnly<> doesn't work here... it forces an initialization that will cause
  // mInCallback to be set back to false before we exit the statement.  Do it by
  // hand instead.
  AutoInCallback aic(this);
#endif

  GraphTime stateComputedTime = StateComputedTime();
  if (stateComputedTime == 0) {
    MonitorAutoLock mon(mGraphImpl->GetMonitor());
    // Because this function is called during cubeb_stream_init (to prefill the
    // audio buffers), it can be that we don't have a message here (because this
    // driver is the first one for this graph), and the graph would exit. Simply
    // return here until we have messages.
    if (!mGraphImpl->MessagesQueued()) {
      PodZero(aBuffer, aFrames * mGraphImpl->AudioChannelCount());
      return aFrames;
    }
    mGraphImpl->SwapMessageQueues();
  }

  uint32_t durationMS = aFrames * 1000 / mSampleRate;

  // For now, simply average the duration with the previous
  // duration so there is some damping against sudden changes.
  if (!mIterationDurationMS) {
    mIterationDurationMS = durationMS;
  } else {
    mIterationDurationMS = (mIterationDurationMS*3) + durationMS;
    mIterationDurationMS /= 4;
  }

  mBuffer.SetBuffer(aBuffer, aFrames);
  // fill part or all with leftover data from last iteration (since we
  // align to Audio blocks)
  mScratchBuffer.Empty(mBuffer);
  // if we totally filled the buffer (and mScratchBuffer isn't empty),
  // we don't need to run an iteration and if we do so we may overflow.
  if (mBuffer.Available()) {

    // State computed time is decided by the audio callback's buffer length. We
    // compute the iteration start and end from there, trying to keep the amount
    // of buffering in the graph constant.
    GraphTime nextStateComputedTime =
      mGraphImpl->RoundUpToNextAudioBlock(stateComputedTime + mBuffer.Available());

    mIterationStart = mIterationEnd;
    // inGraph is the number of audio frames there is between the state time and
    // the current time, i.e. the maximum theoretical length of the interval we
    // could use as [mIterationStart; mIterationEnd].
    GraphTime inGraph = stateComputedTime - mIterationStart;
    // We want the interval [mIterationStart; mIterationEnd] to be before the
    // interval [stateComputedTime; nextStateComputedTime]. We also want
    // the distance between these intervals to be roughly equivalent each time, to
    // ensure there is no clock drift between current time and state time. Since
    // we can't act on the state time because we have to fill the audio buffer, we
    // reclock the current time against the state time, here.
    mIterationEnd = mIterationStart + 0.8 * inGraph;

    STREAM_LOG(LogLevel::Debug, ("interval[%ld; %ld] state[%ld; %ld] (frames: %ld) (durationMS: %u) (duration ticks: %ld)\n",
                              (long)mIterationStart, (long)mIterationEnd,
                              (long)stateComputedTime, (long)nextStateComputedTime,
                              (long)aFrames, (uint32_t)durationMS,
                              (long)(nextStateComputedTime - stateComputedTime)));

    mCurrentTimeStamp = TimeStamp::Now();

    if (stateComputedTime < mIterationEnd) {
      STREAM_LOG(LogLevel::Warning, ("Media graph global underrun detected"));
      mIterationEnd = stateComputedTime;
    }

    stillProcessing = mGraphImpl->OneIteration(nextStateComputedTime);
  } else {
    NS_WARNING("DataCallback buffer filled entirely from scratch buffer, skipping iteration.");
    stillProcessing = true;
  }

  mBuffer.BufferFilled();

  if (mNextDriver && stillProcessing) {
    {
      // If the audio stream has not been started by the previous driver or
      // the graph itself, keep it alive.
      MonitorAutoLock mon(mGraphImpl->GetMonitor());
      if (!IsStarted()) {
        return aFrames;
      }
    }
    STREAM_LOG(LogLevel::Debug, ("Switching to system driver."));
    mNextDriver->SetGraphTime(this, mIterationStart, mIterationEnd);
    mGraphImpl->SetCurrentDriver(mNextDriver);
    mNextDriver->Start();
    // Returning less than aFrames starts the draining and eventually stops the
    // audio thread. This function will never get called again.
    return aFrames - 1;
  }

  if (!stillProcessing) {
    LIFECYCLE_LOG("Stopping audio thread for MediaStreamGraph %p", this);
    return aFrames - 1;
  }
  return aFrames;
}

void
AudioCallbackDriver::StateCallback(cubeb_state aState)
{
  STREAM_LOG(LogLevel::Debug, ("AudioCallbackDriver State: %d", aState));
  if (aState == CUBEB_STATE_ERROR) {
    // Fall back to a driver using a normal thread.
    MonitorAutoLock lock(GraphImpl()->GetMonitor());
    SystemClockDriver* nextDriver = new SystemClockDriver(GraphImpl());
    mNextDriver = nextDriver;
    DebugOnly<bool> found = mGraphImpl->RemoveMixerCallback(this);
    nextDriver->SetGraphTime(this, mIterationStart, mIterationEnd);
    mGraphImpl->SetCurrentDriver(nextDriver);
    nextDriver->Start();
  }
}

void
AudioCallbackDriver::MixerCallback(AudioDataValue* aMixedBuffer,
                                   AudioSampleFormat aFormat,
                                   uint32_t aChannels,
                                   uint32_t aFrames,
                                   uint32_t aSampleRate)
{
  uint32_t toWrite = mBuffer.Available();

  if (!mBuffer.Available()) {
    NS_WARNING("DataCallback buffer full, expect frame drops.");
  }

  MOZ_ASSERT(mBuffer.Available() <= aFrames);

  mBuffer.WriteFrames(aMixedBuffer, mBuffer.Available());
  MOZ_ASSERT(mBuffer.Available() == 0, "Missing frames to fill audio callback's buffer.");

  DebugOnly<uint32_t> written = mScratchBuffer.Fill(aMixedBuffer + toWrite * aChannels, aFrames - toWrite);
  NS_WARN_IF_FALSE(written == aFrames - toWrite, "Dropping frames.");
};

void AudioCallbackDriver::PanOutputIfNeeded(bool aMicrophoneActive)
{
#ifdef XP_MACOSX
  cubeb_device* out;
  int rv;
  char name[128];
  size_t length = sizeof(name);

  rv = sysctlbyname("hw.model", name, &length, NULL, 0);
  if (rv) {
    return;
  }

  if (!strncmp(name, "MacBookPro", 10)) {
    if (cubeb_stream_get_current_device(mAudioStream, &out) == CUBEB_OK) {
      // Check if we are currently outputing sound on external speakers.
      if (!strcmp(out->output_name, "ispk")) {
        // Pan everything to the right speaker.
        if (aMicrophoneActive) {
          if (cubeb_stream_set_panning(mAudioStream, 1.0) != CUBEB_OK) {
            NS_WARNING("Could not pan audio output to the right.");
          }
        } else {
          if (cubeb_stream_set_panning(mAudioStream, 0.0) != CUBEB_OK) {
            NS_WARNING("Could not pan audio output to the center.");
          }
        }
      } else {
        if (cubeb_stream_set_panning(mAudioStream, 0.0) != CUBEB_OK) {
          NS_WARNING("Could not pan audio output to the center.");
        }
      }
      cubeb_stream_device_destroy(mAudioStream, out);
    }
  }
#endif
}

void
AudioCallbackDriver::DeviceChangedCallback() {
  MonitorAutoLock mon(mGraphImpl->GetMonitor());
  PanOutputIfNeeded(mMicrophoneActive);
  // On OSX, changing the output device causes the audio thread to no call the
  // audio callback, so we're unable to process real-time input data, and this
  // results in latency building up.
  // We switch to a system driver until audio callbacks are called again, so we
  // still pull from the input stream, so that everything works apart from the
  // audio output.
#ifdef XP_MACOSX
  // Don't bother doing the device switching dance if the graph is not RUNNING
  // (starting up, shutting down), because we haven't started pulling from the
  // SourceMediaStream.
  if (!GraphImpl()->Running()) {
    return;
  }

  if (mSelfReference) {
    return;
  }
  STREAM_LOG(LogLevel::Error, ("Switching to SystemClockDriver during output switch"));
  mSelfReference.Take(this);
  mCallbackReceivedWhileSwitching = 0;
  mNextDriver = new SystemClockDriver(GraphImpl());
  mNextDriver->SetGraphTime(this, mIterationStart, mIterationEnd);
  mGraphImpl->SetCurrentDriver(mNextDriver);
  mNextDriver->Start();
#endif
}

void
AudioCallbackDriver::SetMicrophoneActive(bool aActive)
{
  MonitorAutoLock mon(mGraphImpl->GetMonitor());

  mMicrophoneActive = aActive;

  PanOutputIfNeeded(mMicrophoneActive);
}

uint32_t
AudioCallbackDriver::IterationDuration()
{
  // The real fix would be to have an API in cubeb to give us the number. Short
  // of that, we approximate it here. bug 1019507
  return mIterationDurationMS;
}

bool
AudioCallbackDriver::IsStarted() {
  mGraphImpl->GetMonitor().AssertCurrentThreadOwns();
  return mStarted;
}

void
AudioCallbackDriver::EnqueueStreamAndPromiseForOperation(MediaStream* aStream,
                                          void* aPromise,
                                          dom::AudioContextOperation aOperation)
{
  MonitorAutoLock mon(mGraphImpl->GetMonitor());
  mPromisesForOperation.AppendElement(StreamAndPromiseForOperation(aStream,
                                                                   aPromise,
                                                                   aOperation));
}

void AudioCallbackDriver::CompleteAudioContextOperations(AsyncCubebOperation aOperation)
{
  nsAutoTArray<StreamAndPromiseForOperation, 1> array;

  // We can't lock for the whole function because AudioContextOperationCompleted
  // will grab the monitor
  {
    MonitorAutoLock mon(GraphImpl()->GetMonitor());
    array.SwapElements(mPromisesForOperation);
  }

  for (uint32_t i = 0; i < array.Length(); i++) {
    StreamAndPromiseForOperation& s = array[i];
    if ((aOperation == AsyncCubebOperation::INIT &&
         s.mOperation == dom::AudioContextOperation::Resume) ||
        (aOperation == AsyncCubebOperation::SHUTDOWN &&
         s.mOperation != dom::AudioContextOperation::Resume)) {

      GraphImpl()->AudioContextOperationCompleted(s.mStream,
                                                  s.mPromise,
                                                  s.mOperation);
      array.RemoveElementAt(i);
      i--;
    }
  }

  if (!array.IsEmpty()) {
    MonitorAutoLock mon(GraphImpl()->GetMonitor());
    mPromisesForOperation.AppendElements(array);
  }
}


} // namespace mozilla