Clean up and refactor platform/AudioDestination

third_party/WebKit/Source/platform/audio/AudioDestination.cpp

Index: third_party/WebKit/Source/platform/audio/AudioDestination.cpp
diff --git a/third_party/WebKit/Source/platform/audio/AudioDestination.cpp b/third_party/WebKit/Source/platform/audio/AudioDestination.cpp
index 72444184e89d65df7c8a29bf9fb77efc2bc4af9b..dcf0ea5841cdf4175ca5d5f325d1167cf89065de 100644
--- a/third_party/WebKit/Source/platform/audio/AudioDestination.cpp
+++ b/third_party/WebKit/Source/platform/audio/AudioDestination.cpp
@@ -29,7 +29,6 @@
 #include "platform/audio/AudioDestination.h"
 
 #include "platform/Histogram.h"
-#include "platform/audio/AudioFIFO.h"
 #include "platform/audio/AudioPullFIFO.h"
 #include "platform/audio/AudioUtilities.h"
 #include "platform/weborigin/SecurityOrigin.h"
@@ -40,138 +39,71 @@
 
 namespace blink {
 
-// Size of the FIFO
-const size_t fifoSize = 8192;
+// FIFO Size.
+//
+// TODO(hongchan): This was estimated based on the largest callback buffer size
+// that we would ever need. The current UMA stats indicates that this is, in
+// fact, probably too small. There are Android devices out there with a size of
+// 8000 or so.  We might need to make this larger. See: crbug.com/670747
+const size_t kFIFOSize = 8192;
 
-// Factory method: Chromium-implementation
 std::unique_ptr<AudioDestination> AudioDestination::create(
     AudioIOCallback& callback,
-    const String& inputDeviceId,
-    unsigned numberOfInputChannels,
     unsigned numberOfOutputChannels,
     float sampleRate,
     PassRefPtr<SecurityOrigin> securityOrigin) {
   return WTF::wrapUnique(new AudioDestination(
-      callback, inputDeviceId, numberOfInputChannels, numberOfOutputChannels,
-      sampleRate, std::move(securityOrigin)));
+      callback, numberOfOutputChannels, sampleRate, std::move(securityOrigin)));
 }
 
 AudioDestination::AudioDestination(AudioIOCallback& callback,
-                                   const String& inputDeviceId,
-                                   unsigned numberOfInputChannels,
                                    unsigned numberOfOutputChannels,
                                    float sampleRate,
                                    PassRefPtr<SecurityOrigin> securityOrigin)
-    : m_callback(callback),
-      m_numberOfOutputChannels(numberOfOutputChannels),
-      m_renderBus(AudioBus::create(numberOfOutputChannels,
-                                   AudioUtilities::kRenderQuantumFrames,
-                                   false)),
+    : m_numberOfOutputChannels(numberOfOutputChannels),
       m_sampleRate(sampleRate),
       m_isPlaying(false),
-      m_framesElapsed(0),
-      m_outputPosition() {
-  // Histogram for audioHardwareBufferSize
-  DEFINE_STATIC_LOCAL(SparseHistogram, hardwareBufferSizeHistogram,
-                      ("WebAudio.AudioDestination.HardwareBufferSize"));
-  // Histogram for the actual callback size used.  Typically, this is the same
-  // as audioHardwareBufferSize, but can be adjusted depending on some
-  // heuristics below.
-  DEFINE_STATIC_LOCAL(SparseHistogram, callbackBufferSizeHistogram,
-                      ("WebAudio.AudioDestination.CallbackBufferSize"));
-
-  // Use the optimal buffer size recommended by the audio backend.
-  size_t recommendedHardwareBufferSize =
-      Platform::current()->audioHardwareBufferSize();
-  m_callbackBufferSize = recommendedHardwareBufferSize;
-
-#if OS(ANDROID)
-  // The optimum low-latency hardware buffer size is usually too small on
-  // Android for WebAudio to render without glitching. So, if it is small, use
-  // a larger size. If it was already large, use the requested size.
-  //
-  // Since WebAudio renders in 128-frame blocks, the small buffer sizes (144
-  // for a Galaxy Nexus), cause significant processing jitter. Sometimes
-  // multiple blocks will processed, but other times will not be since the FIFO
-  // can satisfy the request. By using a larger callbackBufferSize, we smooth
-  // out the jitter.
-  const size_t kSmallBufferSize = 1024;
-  const size_t kDefaultCallbackBufferSize = 2048;
-
-  if (m_callbackBufferSize <= kSmallBufferSize)
-    m_callbackBufferSize = kDefaultCallbackBufferSize;
-
-  LOG(INFO) << "audioHardwareBufferSize = " << recommendedHardwareBufferSize;
-  LOG(INFO) << "callbackBufferSize      = " << m_callbackBufferSize;
-#endif
-
-  // Quick exit if the requested size is too large.
-  DCHECK_LE(m_callbackBufferSize + AudioUtilities::kRenderQuantumFrames,
-            fifoSize);
-  if (m_callbackBufferSize + AudioUtilities::kRenderQuantumFrames > fifoSize)
-    return;
-
-  m_audioDevice = WTF::wrapUnique(Platform::current()->createAudioDevice(
-      m_callbackBufferSize, numberOfInputChannels, numberOfOutputChannels,
-      sampleRate, this, inputDeviceId, std::move(securityOrigin)));
-  ASSERT(m_audioDevice);
-
-  // Record the sizes if we successfully created an output device.
-  hardwareBufferSizeHistogram.sample(recommendedHardwareBufferSize);
-  callbackBufferSizeHistogram.sample(m_callbackBufferSize);
-
-  // Create a FIFO to handle the possibility of the callback size
-  // not being a multiple of the render size. If the FIFO already
-  // contains enough data, the data will be provided directly.
-  // Otherwise, the FIFO will call the provider enough times to
-  // satisfy the request for data.
-  m_fifo =
-      WTF::wrapUnique(new AudioPullFIFO(*this, numberOfOutputChannels, fifoSize,
-                                        AudioUtilities::kRenderQuantumFrames));
+      m_callback(callback),
+      m_outputBus(AudioBus::create(numberOfOutputChannels,
+                                   AudioUtilities::kRenderQuantumFrames,
+                                   false)),
+      m_framesElapsed(0) {
+  // Calculate the optimum buffer size first.
+  if (calculateBufferSize()) {
+    // Create WebAudioDevice. blink::WebAudioDevice is designed to support the
+    // local input (e.g. loopback from OS audio system), but Chromium's media
+    // renderer does not support it currently. Thus, we use zero for the number
+    // of input channels.
+    m_webAudioDevice = WTF::wrapUnique(Platform::current()->createAudioDevice(
+        m_callbackBufferSize, 0, numberOfOutputChannels, sampleRate, this,
+        String(), std::move(securityOrigin)));
+    DCHECK(m_webAudioDevice);
+
+    // Create a FIFO.
+    m_fifo = WTF::wrapUnique(
+        new AudioPullFIFO(*this, numberOfOutputChannels, kFIFOSize,
+                          AudioUtilities::kRenderQuantumFrames));
+  } else {
+    NOTREACHED();
+  }
 }
 
 AudioDestination::~AudioDestination() {
   stop();
 }
 
-void AudioDestination::start() {
-  if (!m_isPlaying && m_audioDevice) {
-    m_audioDevice->start();
-    m_isPlaying = true;
-  }
-}
-
-void AudioDestination::stop() {
-  if (m_isPlaying && m_audioDevice) {
-    m_audioDevice->stop();
-    m_isPlaying = false;
-  }
-}
-
-float AudioDestination::hardwareSampleRate() {
-  return static_cast<float>(Platform::current()->audioHardwareSampleRate());
-}
-
-unsigned long AudioDestination::maxChannelCount() {
-  return static_cast<float>(Platform::current()->audioHardwareOutputChannels());
-}
-
-void AudioDestination::render(const WebVector<float*>& audioData,
+void AudioDestination::render(const WebVector<float*>& destinationData,
                               size_t numberOfFrames,
                               double delay,
                               double delayTimestamp,
                               size_t priorFramesSkipped) {
-  bool isNumberOfChannelsGood = audioData.size() == m_numberOfOutputChannels;
-  if (!isNumberOfChannelsGood) {
-    ASSERT_NOT_REACHED();
+  DCHECK_EQ(destinationData.size(), m_numberOfOutputChannels);
+  if (destinationData.size() != m_numberOfOutputChannels)
     return;
-  }
 
-  bool isBufferSizeGood = numberOfFrames == m_callbackBufferSize;
-  if (!isBufferSizeGood) {
-    ASSERT_NOT_REACHED();
+  DCHECK_EQ(numberOfFrames, m_callbackBufferSize);
+  if (numberOfFrames != m_callbackBufferSize)
     return;
-  }
 
   m_framesElapsed -= std::min(m_framesElapsed, priorFramesSkipped);
   double outputPosition =
@@ -180,18 +112,20 @@ void AudioDestination::render(const WebVector<float*>& audioData,
   m_outputPosition.timestamp = delayTimestamp;
   m_outputPositionReceivedTimestamp = base::TimeTicks::Now();
 
+  // Associate the destination data array with the output bus then fill the
+  // FIFO.
   for (unsigned i = 0; i < m_numberOfOutputChannels; ++i)
-    m_renderBus->setChannelMemory(i, audioData[i], numberOfFrames);
-
-  m_fifo->consume(m_renderBus.get(), numberOfFrames);
+    m_outputBus->setChannelMemory(i, destinationData[i], numberOfFrames);
+  m_fifo->consume(m_outputBus.get(), numberOfFrames);
 
   m_framesElapsed += numberOfFrames;
 }
 
-void AudioDestination::provideInput(AudioBus* bus, size_t framesToProcess) {
+void AudioDestination::provideInput(AudioBus* outputBus,
+                                    size_t framesToProcess) {
   AudioIOPosition outputPosition = m_outputPosition;
 
-  // If platfrom buffer is more than two times longer than |framesToProcess|
+  // If platform buffer is more than two times longer than |framesToProcess|
   // we do not want output position to get stuck so we promote it
   // using the elapsed time from the moment it was initially obtained.
   if (m_callbackBufferSize > framesToProcess * 2) {
@@ -206,7 +140,81 @@ void AudioDestination::provideInput(AudioBus* bus, size_t framesToProcess) {
   if (outputPosition.position < 0.0)
     outputPosition.position = 0.0;
 
-  m_callback.render(nullptr, bus, framesToProcess, outputPosition);
+  // To fill the FIFO, start the render call chain of the destination node.
+  m_callback.render(nullptr, outputBus, framesToProcess, outputPosition);
+}
+
+void AudioDestination::start() {
+  if (m_webAudioDevice && !m_isPlaying) {
+    m_webAudioDevice->start();
+    m_isPlaying = true;
+  }
+}
+
+void AudioDestination::stop() {
+  if (m_webAudioDevice && m_isPlaying) {
+    m_webAudioDevice->stop();
+    m_isPlaying = false;
+  }
+}
+
+size_t AudioDestination::hardwareBufferSize() {
+  return Platform::current()->audioHardwareBufferSize();
+}
+
+float AudioDestination::hardwareSampleRate() {
+  return static_cast<float>(Platform::current()->audioHardwareSampleRate());
+}
+
+unsigned long AudioDestination::maxChannelCount() {
+  return static_cast<unsigned long>(
+      Platform::current()->audioHardwareOutputChannels());
+}
+
+bool AudioDestination::calculateBufferSize() {
+  // Use the optimal buffer size recommended by the audio backend.
+  size_t recommendedHardwareBufferSize = hardwareBufferSize();
+  m_callbackBufferSize = recommendedHardwareBufferSize;
+
+#if OS(ANDROID)
+  // The optimum low-latency hardware buffer size is usually too small on
+  // Android for WebAudio to render without glitching. So, if it is small, use a
+  // larger size. If it was already large, use the requested size.
+  //
+  // Since WebAudio renders in 128-frame blocks, the small buffer sizes (144 for
+  // a Galaxy Nexus), cause significant processing jitter. Sometimes multiple
+  // blocks will processed, but other times will not be since the FIFO can
+  // satisfy the request. By using a larger callbackBufferSize, we smooth out
+  // the jitter.
+  const size_t kSmallBufferSize = 1024;
+  const size_t kDefaultCallbackBufferSize = 2048;
+
+  if (m_callbackBufferSize <= kSmallBufferSize)
+    m_callbackBufferSize = kDefaultCallbackBufferSize;
+
+  LOG(INFO) << "audioHardwareBufferSize = " << recommendedHardwareBufferSize;
+  LOG(INFO) << "callbackBufferSize      = " << m_callbackBufferSize;
+#endif
+
+  // Histogram for audioHardwareBufferSize
+  DEFINE_STATIC_LOCAL(SparseHistogram, hardwareBufferSizeHistogram,
+                      ("WebAudio.AudioDestination.HardwareBufferSize"));
+
+  // Histogram for the actual callback size used.  Typically, this is the same
+  // as audioHardwareBufferSize, but can be adjusted depending on some
+  // heuristics below.
+  DEFINE_STATIC_LOCAL(SparseHistogram, callbackBufferSizeHistogram,
+                      ("WebAudio.AudioDestination.CallbackBufferSize"));
+
+  // Record the sizes if we successfully created an output device.
+  hardwareBufferSizeHistogram.sample(recommendedHardwareBufferSize);
+  callbackBufferSizeHistogram.sample(m_callbackBufferSize);
+
+  // Check if the requested buffer size is too large.
+  bool isBufferSizeValid =
+      m_callbackBufferSize + AudioUtilities::kRenderQuantumFrames <= kFIFOSize;
+  DCHECK(isBufferSizeValid);
+  return isBufferSizeValid;
 }
 
 }  // namespace blink