Add WebThread in AudioDestination to support AudioWorkletThread

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 ff053c2dd65a801f89c79d8f8588ba8f724af20e..c2bd7fdea8980494957fb345ead142caab9b4016 100644
--- a/third_party/WebKit/Source/platform/audio/AudioDestination.cpp
+++ b/third_party/WebKit/Source/platform/audio/AudioDestination.cpp
@@ -29,7 +29,9 @@
 #include "platform/audio/AudioDestination.h"
 
 #include <memory>
+#include "platform/CrossThreadFunctional.h"
 #include "platform/Histogram.h"
+#include "platform/WebTaskRunner.h"
 #include "platform/audio/AudioUtilities.h"
 #include "platform/audio/PushPullFIFO.h"
 #include "platform/weborigin/SecurityOrigin.h"
@@ -37,6 +39,7 @@
 #include "public/platform/Platform.h"
 #include "public/platform/WebAudioLatencyHint.h"
 #include "public/platform/WebSecurityOrigin.h"
+#include "public/platform/WebThread.h"
 
 namespace blink {
 
@@ -58,21 +61,27 @@ std::unique_ptr<AudioDestination> AudioDestination::Create(
                            std::move(security_origin)));
 }
 
-AudioDestination::AudioDestination(AudioIOCallback& callback,
+AudioDestination::AudioDestination(AudioIOCallback& web_audio_render_callback,
                                    unsigned number_of_output_channels,
                                    const WebAudioLatencyHint& latency_hint,
                                    PassRefPtr<SecurityOrigin> security_origin)
     : number_of_output_channels_(number_of_output_channels),
       is_playing_(false),
-      callback_(callback),
+      // callback_(callback),
       output_bus_(AudioBus::Create(number_of_output_channels,
                                    AudioUtilities::kRenderQuantumFrames,
                                    false)),
-      render_bus_(AudioBus::Create(number_of_output_channels,
-                                   AudioUtilities::kRenderQuantumFrames)),
-      fifo_(WTF::WrapUnique(
-          new PushPullFIFO(number_of_output_channels, kFIFOSize))),
+      // render_bus_(AudioBus::Create(number_of_output_channels,
+      //                              AudioUtilities::kRenderQuantumFrames)),
       frames_elapsed_(0) {
+  // Create a thread |WebThread| for WebAudio graph rendering.
+  rendering_thread_ = WTF::WrapUnique(
+      Platform::Current()->CreateThread("WebAudio Rendering Thread"));
+
+  fifo_ = WTF::WrapUnique(new PushPullFIFO(number_of_output_channels, kFIFOSize,
+                                           rendering_thread_->ThreadId(),
+                                           web_audio_render_callback));
+
   // 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
@@ -97,6 +106,9 @@ void AudioDestination::Render(const WebVector<float*>& destination_data,
                               double delay,
                               double delay_timestamp,
                               size_t prior_frames_skipped) {
+  // This this method is called by AudioDeviceThread.
+  DCHECK(!IsRenderingThread());
+
   CHECK_EQ(destination_data.size(), number_of_output_channels_);
   CHECK_EQ(number_of_frames, callback_buffer_size_);
 
@@ -106,51 +118,73 @@ void AudioDestination::Render(const WebVector<float*>& destination_data,
   if (!fifo_ || fifo_->length() < number_of_frames)

[o1ka, 2017/04/13 08:36:53]

Are you keeping silent returns?

[hongchan, 2017/04/14 16:31:48]

This inexplicable case happens only on Android. If this check fails, what else
can we do? Until we figure out why I think this is the best we can do. I rather
not fix this here.

     return;
 
-  frames_elapsed_ -= std::min(frames_elapsed_, prior_frames_skipped);
-  double output_position =
-      frames_elapsed_ / static_cast<double>(web_audio_device_->SampleRate()) -
-      delay;
-  output_position_.position = output_position;
-  output_position_.timestamp = delay_timestamp;
-  output_position_received_timestamp_ = base::TimeTicks::Now();
-
   // Associate the destination data array with the output bus then fill the
   // FIFO.
   for (unsigned i = 0; i < number_of_output_channels_; ++i)
     output_bus_->SetChannelMemory(i, destination_data[i], number_of_frames);
 
-  // Number of frames to render via WebAudio graph. |framesToRender > 0| means
-  // the frames in FIFO is not enough to fulfill the requested frames from the
-  // audio device.
-  size_t frames_to_render = number_of_frames > fifo_->FramesAvailable()
-                                ? number_of_frames - fifo_->FramesAvailable()
-                                : 0;
-
-  for (size_t pushed_frames = 0; pushed_frames < frames_to_render;
-       pushed_frames += AudioUtilities::kRenderQuantumFrames) {
-    // 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 (callback_buffer_size_ > AudioUtilities::kRenderQuantumFrames * 2) {
-      double delta =
-          (base::TimeTicks::Now() - output_position_received_timestamp_)
-              .InSecondsF();
-      output_position_.position += delta;
-      output_position_.timestamp += delta;
-    }
-
-    // Some implementations give only rough estimation of |delay| so
-    // we might have negative estimation |outputPosition| value.
-    if (output_position_.position < 0.0)
-      output_position_.position = 0.0;
-
-    // Process WebAudio graph and push the rendered output to FIFO.
-    callback_.Render(nullptr, render_bus_.Get(),
-                     AudioUtilities::kRenderQuantumFrames, output_position_);
-    fifo_->Push(render_bus_.Get());
-  }
+  rendering_thread_->GetWebTaskRunner()->PostTask(
+      BLINK_FROM_HERE,
+      CrossThreadBind(&AudioDestination::RequestRenderOnWebThread,
+                      CrossThreadUnretained(this), number_of_frames, delay,
+                      delay_timestamp, prior_frames_skipped));
 
   fifo_->Pull(output_bus_.Get(), number_of_frames);
+}
+
+void AudioDestination::RequestRenderOnWebThread(size_t number_of_frames,
+                                                double delay,
+                                                double delay_timestamp,
+                                                size_t prior_frames_skipped) {
+  // This this method is called by WebAudio rendering thread.
+  DCHECK(IsRenderingThread());
+
+  frames_elapsed_ -= std::min(frames_elapsed_, prior_frames_skipped);
+
+  AudioIOPosition output_position;
+  output_position.position =
+      frames_elapsed_ / static_cast<double>(web_audio_device_->SampleRate()) -
+      delay;
+  output_position.timestamp = delay_timestamp;
+
+  fifo_->FillRequestedFrames(number_of_frames, callback_buffer_size_,
+                             output_position);
+
+  // double output_position =
+  //     frames_elapsed_ / static_cast<double>(web_audio_device_->SampleRate()) -
+  //     delay;

[o1ka, 2017/04/13 08:36:53]

It's really inconvenient to review patches with commented out parts like this.
Could you please load a clean patch next time?

[hongchan, 2017/04/14 16:31:48]

I am terribly sorry about this mistake. :(

+  // output_position_.position = output_position;
+  // output_position_.timestamp = delay_timestamp;
+  // output_position_received_timestamp_ = base::TimeTicks::Now();
+
+  // Number of frames to render via WebAudio graph. |frames_to_render > 0| means
+  // the frames in FIFO is not enough to fulfill the requested frames from the
+  // audio device.
+  // size_t frames_to_render = fifo_->GetFramesToRender(number_of_frames);
+
+  // for (size_t pushed_frames = 0; pushed_frames < frames_to_render;
+  //      pushed_frames += AudioUtilities::kRenderQuantumFrames) {
+  //   // 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 (callback_buffer_size_ > AudioUtilities::kRenderQuantumFrames * 2) {
+  //     double delta =
+  //         (base::TimeTicks::Now() - output_position_received_timestamp_)
+  //             .InSecondsF();
+  //     output_position_.position += delta;
+  //     output_position_.timestamp += delta;
+  //   }
+
+  //   // Some implementations give only rough estimation of |delay| so
+  //   // we might have negative estimation |outputPosition| value.
+  //   if (output_position_.position < 0.0)
+  //     output_position_.position = 0.0;
+
+  //   // Process WebAudio graph and push the rendered output to FIFO.
+  //   callback_.Render(nullptr, render_bus_.Get(),
+  //                    AudioUtilities::kRenderQuantumFrames, output_position_);
+  //   fifo_->Push(render_bus_.Get());
+  // }
 
   frames_elapsed_ += number_of_frames;
 }
@@ -204,4 +238,9 @@ bool AudioDestination::CheckBufferSize() {
   return is_buffer_size_valid;
 }
 
+bool AudioDestination::IsRenderingThread() {
+  return static_cast<ThreadIdentifier>(rendering_thread_->ThreadId()) ==
+         CurrentThread();
+}
+
 }  // namespace blink