gecko/content/media/AudioStream.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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 <stdio.h>
#include <math.h>
#include "prlog.h"
#include "prmem.h"
#include "prdtoa.h"
#include "nsAutoPtr.h"
#include "AudioStream.h"
#include "nsAlgorithm.h"
#include "VideoUtils.h"
#include "mozilla/Monitor.h"
#include "mozilla/Mutex.h"
extern "C" {
#include "sydneyaudio/sydney_audio.h"
}
#include "nsThreadUtils.h"
#include "mozilla/Preferences.h"

#if defined(MOZ_CUBEB)
#include "nsAutoRef.h"
#include "cubeb/cubeb.h"

template <>
class nsAutoRefTraits<cubeb_stream> : public nsPointerRefTraits<cubeb_stream>
{
public:
  static void Release(cubeb_stream* aStream) { cubeb_stream_destroy(aStream); }
};

#endif

namespace mozilla {

#if defined(XP_MACOSX)
#define SA_PER_STREAM_VOLUME 1
#endif

#ifdef PR_LOGGING
PRLogModuleInfo* gAudioStreamLog = nullptr;
#endif

static const uint32_t FAKE_BUFFER_SIZE = 176400;

// Number of milliseconds per second.
static const int64_t MS_PER_S = 1000;

class nsNativeAudioStream : public AudioStream
{
 public:
  NS_DECL_ISUPPORTS

  ~nsNativeAudioStream();
  nsNativeAudioStream();

  nsresult Init(int32_t aNumChannels, int32_t aRate,
                const dom::AudioChannelType aAudioChannelType);
  void Shutdown();
  nsresult Write(const AudioDataValue* aBuf, uint32_t aFrames);
  uint32_t Available();
  void SetVolume(double aVolume);
  void Drain();
  void Pause();
  void Resume();
  int64_t GetPosition();
  int64_t GetPositionInFrames();
  bool IsPaused();
  int32_t GetMinWriteSize();

 private:

  double mVolume;
  void* mAudioHandle;

  // True if this audio stream is paused.
  bool mPaused;

  // True if this stream has encountered an error.
  bool mInError;

};

#define PREF_VOLUME_SCALE "media.volume_scale"
#define PREF_USE_CUBEB "media.use_cubeb"
#define PREF_CUBEB_LATENCY "media.cubeb_latency_ms"

static Mutex* gAudioPrefsLock = nullptr;
static double gVolumeScale;
static bool gUseCubeb;
static uint32_t gCubebLatency;

static int PrefChanged(const char* aPref, void* aClosure)
{
  if (strcmp(aPref, PREF_VOLUME_SCALE) == 0) {
    nsAdoptingString value = Preferences::GetString(aPref);
    MutexAutoLock lock(*gAudioPrefsLock);
    if (value.IsEmpty()) {
      gVolumeScale = 1.0;
    } else {
      NS_ConvertUTF16toUTF8 utf8(value);
      gVolumeScale = NS_MAX<double>(0, PR_strtod(utf8.get(), nullptr));
    }
  } else if (strcmp(aPref, PREF_USE_CUBEB) == 0) {
#ifdef MOZ_WIDGET_GONK
    bool value = Preferences::GetBool(aPref, false);
#else
    bool value = Preferences::GetBool(aPref, true);
#endif
    MutexAutoLock lock(*gAudioPrefsLock);
    gUseCubeb = value;
  } else if (strcmp(aPref, PREF_CUBEB_LATENCY) == 0) {
    // Arbitrary default stream latency of 100ms.  The higher this
    // value, the longer stream volume changes will take to become
    // audible.
    uint32_t value = Preferences::GetUint(aPref, 100);
    MutexAutoLock lock(*gAudioPrefsLock);
    gCubebLatency = NS_MIN<uint32_t>(NS_MAX<uint32_t>(value, 20), 1000);
  }
  return 0;
}

static double GetVolumeScale()
{
  MutexAutoLock lock(*gAudioPrefsLock);
  return gVolumeScale;
}

#if defined(MOZ_CUBEB)
static bool GetUseCubeb()
{
  MutexAutoLock lock(*gAudioPrefsLock);
  return gUseCubeb;
}

static cubeb* gCubebContext;

static cubeb* GetCubebContext()
{
  MutexAutoLock lock(*gAudioPrefsLock);
  if (gCubebContext ||
      cubeb_init(&gCubebContext, "AudioStream") == CUBEB_OK) {
    return gCubebContext;
  }
  NS_WARNING("cubeb_init failed");
  return nullptr;
}

static uint32_t GetCubebLatency()
{
  MutexAutoLock lock(*gAudioPrefsLock);
  return gCubebLatency;
}
#endif

static sa_stream_type_t ConvertChannelToSAType(dom::AudioChannelType aType)
{
  switch(aType) {
    case dom::AUDIO_CHANNEL_NORMAL:
      return SA_STREAM_TYPE_SYSTEM;
    case dom::AUDIO_CHANNEL_CONTENT:
      return SA_STREAM_TYPE_MUSIC;
    case dom::AUDIO_CHANNEL_NOTIFICATION:
      return SA_STREAM_TYPE_NOTIFICATION;
    case dom::AUDIO_CHANNEL_ALARM:
      return SA_STREAM_TYPE_ALARM;
    case dom::AUDIO_CHANNEL_TELEPHONY:
      return SA_STREAM_TYPE_VOICE_CALL;
    case dom::AUDIO_CHANNEL_PUBLICNOTIFICATION:
      return SA_STREAM_TYPE_ENFORCED_AUDIBLE;
    default:
      NS_ERROR("The value of AudioChannelType is invalid");
      return SA_STREAM_TYPE_MAX;
  }
}

void AudioStream::InitLibrary()
{
#ifdef PR_LOGGING
  gAudioStreamLog = PR_NewLogModule("AudioStream");
#endif
  gAudioPrefsLock = new Mutex("AudioStream::gAudioPrefsLock");
  PrefChanged(PREF_VOLUME_SCALE, nullptr);
  Preferences::RegisterCallback(PrefChanged, PREF_VOLUME_SCALE);
#if defined(MOZ_CUBEB)
  PrefChanged(PREF_USE_CUBEB, nullptr);
  Preferences::RegisterCallback(PrefChanged, PREF_USE_CUBEB);
  PrefChanged(PREF_CUBEB_LATENCY, nullptr);
  Preferences::RegisterCallback(PrefChanged, PREF_CUBEB_LATENCY);
#endif
}

void AudioStream::ShutdownLibrary()
{
  Preferences::UnregisterCallback(PrefChanged, PREF_VOLUME_SCALE);
#if defined(MOZ_CUBEB)
  Preferences::UnregisterCallback(PrefChanged, PREF_USE_CUBEB);
#endif
  delete gAudioPrefsLock;
  gAudioPrefsLock = nullptr;

#if defined(MOZ_CUBEB)
  if (gCubebContext) {
    cubeb_destroy(gCubebContext);
    gCubebContext = nullptr;
  }
#endif
}

nsIThread *
AudioStream::GetThread()
{
  if (!mAudioPlaybackThread) {
    NS_NewNamedThread("Audio Stream",
                      getter_AddRefs(mAudioPlaybackThread),
                      nullptr,
                      MEDIA_THREAD_STACK_SIZE);
  }
  return mAudioPlaybackThread;
}

class AsyncShutdownPlaybackThread : public nsRunnable
{
public:
  AsyncShutdownPlaybackThread(nsIThread* aThread) : mThread(aThread) {}
  NS_IMETHODIMP Run() { return mThread->Shutdown(); }
private:
  nsCOMPtr<nsIThread> mThread;
};

AudioStream::~AudioStream()
{
  if (mAudioPlaybackThread) {
    nsCOMPtr<nsIRunnable> event = new AsyncShutdownPlaybackThread(mAudioPlaybackThread);
    NS_DispatchToMainThread(event);
  }
}

nsNativeAudioStream::nsNativeAudioStream() :
  mVolume(1.0),
  mAudioHandle(0),
  mPaused(false),
  mInError(false)
{
}

nsNativeAudioStream::~nsNativeAudioStream()
{
  Shutdown();
}

NS_IMPL_THREADSAFE_ISUPPORTS0(nsNativeAudioStream)

nsresult nsNativeAudioStream::Init(int32_t aNumChannels, int32_t aRate,
                                   const dom::AudioChannelType aAudioChannelType)
{
  mRate = aRate;
  mChannels = aNumChannels;

  if (sa_stream_create_pcm(reinterpret_cast<sa_stream_t**>(&mAudioHandle),
                           NULL,
                           SA_MODE_WRONLY,
                           SA_PCM_FORMAT_S16_NE,
                           aRate,
                           aNumChannels) != SA_SUCCESS) {
    mAudioHandle = nullptr;
    mInError = true;
    PR_LOG(gAudioStreamLog, PR_LOG_ERROR, ("nsNativeAudioStream: sa_stream_create_pcm error"));
    return NS_ERROR_FAILURE;
  }

  int saError = sa_stream_set_stream_type(static_cast<sa_stream_t*>(mAudioHandle),
                       ConvertChannelToSAType(aAudioChannelType));
  if (saError != SA_SUCCESS && saError != SA_ERROR_NOT_SUPPORTED) {
    mAudioHandle = nullptr;
    mInError = true;
    PR_LOG(gAudioStreamLog, PR_LOG_ERROR, ("nsNativeAudioStream: sa_stream_set_stream_type error"));
    return NS_ERROR_FAILURE;
  }

  if (sa_stream_open(static_cast<sa_stream_t*>(mAudioHandle)) != SA_SUCCESS) {
    sa_stream_destroy(static_cast<sa_stream_t*>(mAudioHandle));
    mAudioHandle = nullptr;
    mInError = true;
    PR_LOG(gAudioStreamLog, PR_LOG_ERROR, ("nsNativeAudioStream: sa_stream_open error"));
    return NS_ERROR_FAILURE;
  }
  mInError = false;

  return NS_OK;
}

void nsNativeAudioStream::Shutdown()
{
  if (!mAudioHandle)
    return;

  sa_stream_destroy(static_cast<sa_stream_t*>(mAudioHandle));
  mAudioHandle = nullptr;
  mInError = true;
}

nsresult nsNativeAudioStream::Write(const AudioDataValue* aBuf, uint32_t aFrames)
{
  NS_ASSERTION(!mPaused, "Don't write audio when paused, you'll block");

  if (mInError)
    return NS_ERROR_FAILURE;

  uint32_t samples = aFrames * mChannels;
  nsAutoArrayPtr<short> s_data(new short[samples]);

  float scaled_volume = float(GetVolumeScale() * mVolume);
  ConvertAudioSamplesWithScale(aBuf, s_data.get(), samples, scaled_volume);

  if (sa_stream_write(static_cast<sa_stream_t*>(mAudioHandle),
                      s_data.get(),
                      samples * sizeof(short)) != SA_SUCCESS)
  {
    PR_LOG(gAudioStreamLog, PR_LOG_ERROR, ("nsNativeAudioStream: sa_stream_write error"));
    mInError = true;
    return NS_ERROR_FAILURE;
  }
  return NS_OK;
}

uint32_t nsNativeAudioStream::Available()
{
  // If the audio backend failed to open, lie and say we'll accept some
  // data.
  if (mInError)
    return FAKE_BUFFER_SIZE;

  size_t s = 0;
  if (sa_stream_get_write_size(static_cast<sa_stream_t*>(mAudioHandle), &s) != SA_SUCCESS)
    return 0;

  return s / mChannels / sizeof(short);
}

void nsNativeAudioStream::SetVolume(double aVolume)
{
  NS_ASSERTION(aVolume >= 0.0 && aVolume <= 1.0, "Invalid volume");
#if defined(SA_PER_STREAM_VOLUME)
  if (sa_stream_set_volume_abs(static_cast<sa_stream_t*>(mAudioHandle), aVolume) != SA_SUCCESS) {
    PR_LOG(gAudioStreamLog, PR_LOG_ERROR, ("nsNativeAudioStream: sa_stream_set_volume_abs error"));
    mInError = true;
  }
#else
  mVolume = aVolume;
#endif
}

void nsNativeAudioStream::Drain()
{
  NS_ASSERTION(!mPaused, "Don't drain audio when paused, it won't finish!");

  if (mInError)
    return;

  int r = sa_stream_drain(static_cast<sa_stream_t*>(mAudioHandle));
  if (r != SA_SUCCESS && r != SA_ERROR_INVALID) {
    PR_LOG(gAudioStreamLog, PR_LOG_ERROR, ("nsNativeAudioStream: sa_stream_drain error"));
    mInError = true;
  }
}

void nsNativeAudioStream::Pause()
{
  if (mInError)
    return;
  mPaused = true;
  sa_stream_pause(static_cast<sa_stream_t*>(mAudioHandle));
}

void nsNativeAudioStream::Resume()
{
  if (mInError)
    return;
  mPaused = false;
  sa_stream_resume(static_cast<sa_stream_t*>(mAudioHandle));
}

int64_t nsNativeAudioStream::GetPosition()
{
  int64_t position = GetPositionInFrames();
  if (position >= 0) {
    return ((USECS_PER_S * position) / mRate);
  }
  return -1;
}

int64_t nsNativeAudioStream::GetPositionInFrames()
{
  if (mInError) {
    return -1;
  }

  sa_position_t positionType = SA_POSITION_WRITE_SOFTWARE;
#if defined(XP_WIN)
  positionType = SA_POSITION_WRITE_HARDWARE;
#endif
  int64_t position = 0;
  if (sa_stream_get_position(static_cast<sa_stream_t*>(mAudioHandle),
                             positionType, &position) == SA_SUCCESS) {
    return position / mChannels / sizeof(short);
  }

  return -1;
}

bool nsNativeAudioStream::IsPaused()
{
  return mPaused;
}

int32_t nsNativeAudioStream::GetMinWriteSize()
{
  size_t size;
  int r = sa_stream_get_min_write(static_cast<sa_stream_t*>(mAudioHandle),
                                  &size);
  if (r == SA_ERROR_NOT_SUPPORTED)
    return 1;
  else if (r != SA_SUCCESS || size > INT32_MAX)
    return -1;

  return static_cast<int32_t>(size / mChannels / sizeof(short));
}

#if defined(MOZ_CUBEB)
class nsCircularByteBuffer
{
public:
  nsCircularByteBuffer()
    : mBuffer(nullptr), mCapacity(0), mStart(0), mCount(0)
  {}

  // Set the capacity of the buffer in bytes.  Must be called before any
  // call to append or pop elements.
  void SetCapacity(uint32_t aCapacity) {
    NS_ABORT_IF_FALSE(!mBuffer, "Buffer allocated.");
    mCapacity = aCapacity;
    mBuffer = new uint8_t[mCapacity];
  }

  uint32_t Length() {
    return mCount;
  }

  uint32_t Capacity() {
    return mCapacity;
  }

  uint32_t Available() {
    return Capacity() - Length();
  }

  // Append aLength bytes from aSrc to the buffer.  Caller must check that
  // sufficient space is available.
  void AppendElements(const uint8_t* aSrc, uint32_t aLength) {
    NS_ABORT_IF_FALSE(mBuffer && mCapacity, "Buffer not initialized.");
    NS_ABORT_IF_FALSE(aLength <= Available(), "Buffer full.");

    uint32_t end = (mStart + mCount) % mCapacity;

    uint32_t toCopy = NS_MIN(mCapacity - end, aLength);
    memcpy(&mBuffer[end], aSrc, toCopy);
    memcpy(&mBuffer[0], aSrc + toCopy, aLength - toCopy);
    mCount += aLength;
  }

  // Remove aSize bytes from the buffer.  Caller must check returned size in
  // aSize{1,2} before using the pointer returned in aData{1,2}.  Caller
  // must not specify an aSize larger than Length().
  void PopElements(uint32_t aSize, void** aData1, uint32_t* aSize1,
                   void** aData2, uint32_t* aSize2) {
    NS_ABORT_IF_FALSE(mBuffer && mCapacity, "Buffer not initialized.");
    NS_ABORT_IF_FALSE(aSize <= Length(), "Request too large.");

    *aData1 = &mBuffer[mStart];
    *aSize1 = NS_MIN(mCapacity - mStart, aSize);
    *aData2 = &mBuffer[0];
    *aSize2 = aSize - *aSize1;
    mCount -= *aSize1 + *aSize2;
    mStart += *aSize1 + *aSize2;
    mStart %= mCapacity;
  }

private:
  nsAutoArrayPtr<uint8_t> mBuffer;
  uint32_t mCapacity;
  uint32_t mStart;
  uint32_t mCount;
};

class nsBufferedAudioStream : public AudioStream
{
 public:
  NS_DECL_ISUPPORTS

  nsBufferedAudioStream();
  ~nsBufferedAudioStream();

  nsresult Init(int32_t aNumChannels, int32_t aRate,
                const dom::AudioChannelType aAudioChannelType);
  void Shutdown();
  nsresult Write(const AudioDataValue* aBuf, uint32_t aFrames);
  uint32_t Available();
  void SetVolume(double aVolume);
  void Drain();
  void Pause();
  void Resume();
  int64_t GetPosition();
  int64_t GetPositionInFrames();
  bool IsPaused();
  int32_t GetMinWriteSize();

private:
  static long DataCallback_S(cubeb_stream*, void* aThis, void* aBuffer, long aFrames)
  {
    return static_cast<nsBufferedAudioStream*>(aThis)->DataCallback(aBuffer, aFrames);
  }

  static void StateCallback_S(cubeb_stream*, void* aThis, cubeb_state aState)
  {
    static_cast<nsBufferedAudioStream*>(aThis)->StateCallback(aState);
  }

  long DataCallback(void* aBuffer, long aFrames);
  void StateCallback(cubeb_state aState);

  // Shared implementation of underflow adjusted position calculation.
  // Caller must own the monitor.
  int64_t GetPositionInFramesUnlocked();

  // The monitor is held to protect all access to member variables.  Write()
  // waits while mBuffer is full; DataCallback() notifies as it consumes
  // data from mBuffer.  Drain() waits while mState is DRAINING;
  // StateCallback() notifies when mState is DRAINED.
  Monitor mMonitor;

  // Sum of silent frames written when DataCallback requests more frames
  // than are available in mBuffer.
  uint64_t mLostFrames;

  // Temporary audio buffer.  Filled by Write() and consumed by
  // DataCallback().  Once mBuffer is full, Write() blocks until sufficient
  // space becomes available in mBuffer.  mBuffer is sized in bytes, not
  // frames.
  nsCircularByteBuffer mBuffer;

  // Software volume level.  Applied during the servicing of DataCallback().
  double mVolume;

  // Owning reference to a cubeb_stream.  cubeb_stream_destroy is called by
  // nsAutoRef's destructor.
  nsAutoRef<cubeb_stream> mCubebStream;

  uint32_t mBytesPerFrame;

  enum StreamState {
    INITIALIZED, // Initialized, playback has not begun.
    STARTED,     // Started by a call to Write() (iff INITIALIZED) or Resume().
    STOPPED,     // Stopped by a call to Pause().
    DRAINING,    // Drain requested.  DataCallback will indicate end of stream
                 // once the remaining contents of mBuffer are requested by
                 // cubeb, after which StateCallback will indicate drain
                 // completion.
    DRAINED,     // StateCallback has indicated that the drain is complete.
    ERRORED      // Stream disabled due to an internal error.
  };

  StreamState mState;
};
#endif

AudioStream* AudioStream::AllocateStream()
{
#if defined(MOZ_CUBEB)
  if (GetUseCubeb()) {
    return new nsBufferedAudioStream();
  }
#endif
  return new nsNativeAudioStream();
}

#if defined(MOZ_CUBEB)
nsBufferedAudioStream::nsBufferedAudioStream()
  : mMonitor("nsBufferedAudioStream"), mLostFrames(0), mVolume(1.0),
    mBytesPerFrame(0), mState(INITIALIZED)
{
}

nsBufferedAudioStream::~nsBufferedAudioStream()
{
  Shutdown();
}

NS_IMPL_THREADSAFE_ISUPPORTS0(nsBufferedAudioStream)

nsresult
nsBufferedAudioStream::Init(int32_t aNumChannels, int32_t aRate,
                            const dom::AudioChannelType aAudioChannelType)
{
  cubeb* cubebContext = GetCubebContext();

  if (!cubebContext || aNumChannels < 0 || aRate < 0) {
    return NS_ERROR_FAILURE;
  }

  mRate = aRate;
  mChannels = aNumChannels;

  cubeb_stream_params params;
  params.rate = aRate;
  params.channels = aNumChannels;
  if (AUDIO_OUTPUT_FORMAT == AUDIO_FORMAT_S16) {
    params.format = CUBEB_SAMPLE_S16NE;
  } else {
    params.format = CUBEB_SAMPLE_FLOAT32NE;
  }
  mBytesPerFrame = sizeof(AudioDataValue) * aNumChannels;

  {
    cubeb_stream* stream;
    if (cubeb_stream_init(cubebContext, &stream, "nsBufferedAudioStream", params,
                          GetCubebLatency(), DataCallback_S, StateCallback_S, this) == CUBEB_OK) {
      mCubebStream.own(stream);
    }
  }

  if (!mCubebStream) {
    return NS_ERROR_FAILURE;
  }

  // Size mBuffer for one second of audio.  This value is arbitrary, and was
  // selected based on the observed behaviour of the existing AudioStream
  // implementations.
  uint32_t bufferLimit = aRate * mBytesPerFrame;
  NS_ABORT_IF_FALSE(bufferLimit % mBytesPerFrame == 0, "Must buffer complete frames");
  mBuffer.SetCapacity(bufferLimit);

  return NS_OK;
}

void
nsBufferedAudioStream::Shutdown()
{
  if (mState == STARTED) {
    Pause();
  }
  if (mCubebStream) {
    mCubebStream.reset();
  }
}

nsresult
nsBufferedAudioStream::Write(const AudioDataValue* aBuf, uint32_t aFrames)
{
  MonitorAutoLock mon(mMonitor);
  if (!mCubebStream || mState == ERRORED) {
    return NS_ERROR_FAILURE;
  }
  NS_ASSERTION(mState == INITIALIZED || mState == STARTED, "Stream write in unexpected state.");

  const uint8_t* src = reinterpret_cast<const uint8_t*>(aBuf);
  uint32_t bytesToCopy = aFrames * mBytesPerFrame;

  while (bytesToCopy > 0) {
    uint32_t available = NS_MIN(bytesToCopy, mBuffer.Available());
    NS_ABORT_IF_FALSE(available % mBytesPerFrame == 0, "Must copy complete frames.");

    mBuffer.AppendElements(src, available);
    src += available;
    bytesToCopy -= available;

    if (mState != STARTED) {
      int r;
      {
        MonitorAutoUnlock mon(mMonitor);
        r = cubeb_stream_start(mCubebStream);
      }
      mState = r == CUBEB_OK ? STARTED : ERRORED;
    }

    if (mState != STARTED) {
      return NS_ERROR_FAILURE;
    }

    if (bytesToCopy > 0) {
      mon.Wait();
    }
  }

  return NS_OK;
}

uint32_t
nsBufferedAudioStream::Available()
{
  MonitorAutoLock mon(mMonitor);
  NS_ABORT_IF_FALSE(mBuffer.Length() % mBytesPerFrame == 0, "Buffer invariant violated.");
  return mBuffer.Available() / mBytesPerFrame;
}

int32_t
nsBufferedAudioStream::GetMinWriteSize()
{
  return 1;
}

void
nsBufferedAudioStream::SetVolume(double aVolume)
{
  MonitorAutoLock mon(mMonitor);
  NS_ABORT_IF_FALSE(aVolume >= 0.0 && aVolume <= 1.0, "Invalid volume");
  mVolume = aVolume;
}

void
nsBufferedAudioStream::Drain()
{
  MonitorAutoLock mon(mMonitor);
  if (mState != STARTED) {
    return;
  }
  mState = DRAINING;
  while (mState == DRAINING) {
    mon.Wait();
  }
}

void
nsBufferedAudioStream::Pause()
{
  MonitorAutoLock mon(mMonitor);
  if (!mCubebStream || mState != STARTED) {
    return;
  }

  int r;
  {
    MonitorAutoUnlock mon(mMonitor);
    r = cubeb_stream_stop(mCubebStream);
  }
  if (mState != ERRORED && r == CUBEB_OK) {
    mState = STOPPED;
  }
}

void
nsBufferedAudioStream::Resume()
{
  MonitorAutoLock mon(mMonitor);
  if (!mCubebStream || mState != STOPPED) {
    return;
  }

  int r;
  {
    MonitorAutoUnlock mon(mMonitor);
    r = cubeb_stream_start(mCubebStream);
  }
  if (mState != ERRORED && r == CUBEB_OK) {
    mState = STARTED;
  }
}

int64_t
nsBufferedAudioStream::GetPosition()
{
  MonitorAutoLock mon(mMonitor);
  int64_t frames = GetPositionInFramesUnlocked();
  if (frames >= 0) {
    return USECS_PER_S * frames / mRate;
  }
  return -1;
}

// This function is miscompiled by PGO with MSVC 2010.  See bug 768333.
#ifdef _MSC_VER
#pragma optimize("", off)
#endif
int64_t
nsBufferedAudioStream::GetPositionInFrames()
{
  MonitorAutoLock mon(mMonitor);
  return GetPositionInFramesUnlocked();
}
#ifdef _MSC_VER
#pragma optimize("", on)
#endif

int64_t
nsBufferedAudioStream::GetPositionInFramesUnlocked()
{
  mMonitor.AssertCurrentThreadOwns();

  if (!mCubebStream || mState == ERRORED) {
    return -1;
  }

  uint64_t position = 0;
  {
    MonitorAutoUnlock mon(mMonitor);
    if (cubeb_stream_get_position(mCubebStream, &position) != CUBEB_OK) {
      return -1;
    }
  }

  // Adjust the reported position by the number of silent frames written
  // during stream underruns.
  uint64_t adjustedPosition = 0;
  if (position >= mLostFrames) {
    adjustedPosition = position - mLostFrames;
  }
  return NS_MIN<uint64_t>(adjustedPosition, INT64_MAX);
}

bool
nsBufferedAudioStream::IsPaused()
{
  MonitorAutoLock mon(mMonitor);
  return mState == STOPPED;
}

long
nsBufferedAudioStream::DataCallback(void* aBuffer, long aFrames)
{
  MonitorAutoLock mon(mMonitor);
  uint32_t bytesWanted = aFrames * mBytesPerFrame;

  // Adjust bytesWanted to fit what is available in mBuffer.
  uint32_t available = NS_MIN(bytesWanted, mBuffer.Length());
  NS_ABORT_IF_FALSE(available % mBytesPerFrame == 0, "Must copy complete frames");

  if (available > 0) {
    // Copy each sample from mBuffer to aBuffer, adjusting the volume during the copy.
    float scaled_volume = float(GetVolumeScale() * mVolume);

    // Fetch input pointers from the ring buffer.
    void* input[2];
    uint32_t input_size[2];
    mBuffer.PopElements(available, &input[0], &input_size[0], &input[1], &input_size[1]);

    uint8_t* output = static_cast<uint8_t*>(aBuffer);
    for (int i = 0; i < 2; ++i) {
      const AudioDataValue* src = static_cast<const AudioDataValue*>(input[i]);
      AudioDataValue* dst = reinterpret_cast<AudioDataValue*>(output);

      ConvertAudioSamplesWithScale(src, dst, input_size[i]/sizeof(AudioDataValue),
                                   scaled_volume);
      output += input_size[i];
    }

    NS_ABORT_IF_FALSE(mBuffer.Length() % mBytesPerFrame == 0, "Must copy complete frames");

    // Notify any blocked Write() call that more space is available in mBuffer.
    mon.NotifyAll();

    // Calculate remaining bytes requested by caller.  If the stream is not
    // draining an underrun has occurred, so fill the remaining buffer with
    // silence.
    bytesWanted -= available;
  }

  if (mState != DRAINING) {
    memset(static_cast<uint8_t*>(aBuffer) + available, 0, bytesWanted);
    mLostFrames += bytesWanted / mBytesPerFrame;
    bytesWanted = 0;
  }

  return aFrames - (bytesWanted / mBytesPerFrame);
}

void
nsBufferedAudioStream::StateCallback(cubeb_state aState)
{
  MonitorAutoLock mon(mMonitor);
  if (aState == CUBEB_STATE_DRAINED) {
    mState = DRAINED;
  } else if (aState == CUBEB_STATE_ERROR) {
    mState = ERRORED;
  }
  mon.NotifyAll();
}
#endif

} // namespace mozilla