media::WebAudioSourceProviderImpl, add support for getting a copy of passing AudioBuses

media/blink/webaudiosourceprovider_impl.cc

Index: media/blink/webaudiosourceprovider_impl.cc
diff --git a/media/blink/webaudiosourceprovider_impl.cc b/media/blink/webaudiosourceprovider_impl.cc
index 5b70a3091ba7760878c7f5d9f80147af4a1292c6..d43a16fb5b1b927eab078c7fb7f952b02aafe3b6 100644
--- a/media/blink/webaudiosourceprovider_impl.cc
+++ b/media/blink/webaudiosourceprovider_impl.cc
@@ -47,14 +47,50 @@ class AutoTryLock {
 
 }  // namespace
 
+// TeeFilter is a RenderCallback implementation that allows for a client to get
+// a copy of the data being rendered by the |renderer_| on Render(). This class
+// also holds to the necessary audio parameters.
+class WebAudioSourceProviderImpl::TeeFilter
+    : public AudioRendererSink::RenderCallback {
+ public:
+  TeeFilter(AudioRendererSink::RenderCallback* renderer,
+            int channels,
+            int sample_rate)
+      : renderer_(renderer), channels_(channels), sample_rate_(sample_rate) {
+    DCHECK(renderer_);
+  }
+  ~TeeFilter() override {}
+
+  // AudioRendererSink::RenderCallback implementation.
+  // These are forwarders to |renderer_| and are here to allow for a client to
+  // get a copy of the rendered audio by SetCopyAudioCallback().
+  int Render(AudioBus* audio_bus,
+             uint32_t delay_milliseconds,
+             uint32_t frames_skipped) override;
+  void OnRenderError() override;
+
+  int channels() const { return channels_; }
+  int sample_rate() const { return sample_rate_; }
+  void set_copy_audio_bus_callback(
+      const WebAudioSourceProviderImpl::CopyAudioCB& callback) {
+    copy_audio_bus_callback_ = callback;
+  }
+
+ private:
+  AudioRendererSink::RenderCallback* const renderer_;
+  const int channels_;
+  const int sample_rate_;
+
+  WebAudioSourceProviderImpl::CopyAudioCB copy_audio_bus_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(TeeFilter);
+};
+
 WebAudioSourceProviderImpl::WebAudioSourceProviderImpl(
     const scoped_refptr<RestartableAudioRendererSink>& sink)
-    : channels_(0),
-      sample_rate_(0),
-      volume_(1.0),
+    : volume_(1.0),
       state_(kStopped),
-      renderer_(NULL),
-      client_(NULL),
+      client_(nullptr),
       sink_(sink),
       weak_factory_(this) {}
 
@@ -74,16 +110,16 @@ void WebAudioSourceProviderImpl::setClient(
     set_format_cb_ = BindToCurrentLoop(base::Bind(
         &WebAudioSourceProviderImpl::OnSetFormat, weak_factory_.GetWeakPtr()));
 
-    // If |renderer_| is set, then run |set_format_cb_| to send |client_|
-    // the current format info. If |renderer_| is not set, then |set_format_cb_|
-    // will get called when Initialize() is called.
-    // Note: Always using |set_format_cb_| ensures we have the same
-    // locking order when calling into |client_|.
-    if (renderer_)
+    // If |tee_filter_| is set, it means we have been Initialize()d - then run
+    // |set_format_cb_| to send |client_| the current format info. Otherwise
+    // |set_format_cb_| will get called when Initialize() is called.
+    // Note: Always using |set_format_cb_| ensures we have the same locking
+    // order when calling into |client_|.
+    if (tee_filter_)
       base::ResetAndReturn(&set_format_cb_).Run();
   } else if (!client && client_) {
     // Restore normal playback.
-    client_ = NULL;
+    client_ = nullptr;
     sink_->SetVolume(volume_);
     if (state_ >= kStarted)
       sink_->Start();
@@ -99,7 +135,8 @@ void WebAudioSourceProviderImpl::provideInput(
     bus_wrapper_ = AudioBus::CreateWrapper(static_cast<int>(audio_data.size()));
   }
 
-  bus_wrapper_->set_frames(static_cast<int>(number_of_frames));
+  const int incoming_number_of_frames = static_cast<int>(number_of_frames);
+  bus_wrapper_->set_frames(incoming_number_of_frames);
   for (size_t i = 0; i < audio_data.size(); ++i)
     bus_wrapper_->SetChannelData(static_cast<int>(i), audio_data[i]);
 
@@ -112,22 +149,19 @@ void WebAudioSourceProviderImpl::provideInput(
     return;
   }
 
-  DCHECK(renderer_);
   DCHECK(client_);
-  DCHECK_EQ(channels_, bus_wrapper_->channels());
-  const int frames = renderer_->Render(bus_wrapper_.get(), 0, 0);
-  if (frames < static_cast<int>(number_of_frames)) {
-    bus_wrapper_->ZeroFramesPartial(
-        frames,
-        static_cast<int>(number_of_frames - frames));
-  }
+  DCHECK(tee_filter_);
+  DCHECK_EQ(tee_filter_->channels(), bus_wrapper_->channels());
+  const int frames = tee_filter_->Render(bus_wrapper_.get(), 0, 0);
+  if (frames < incoming_number_of_frames)
+    bus_wrapper_->ZeroFramesPartial(frames, incoming_number_of_frames - frames);
 
   bus_wrapper_->Scale(volume_);
 }
 
 void WebAudioSourceProviderImpl::Start() {
   base::AutoLock auto_lock(sink_lock_);
-  DCHECK(renderer_);
+  DCHECK(tee_filter_);
   DCHECK_EQ(state_, kStopped);
   state_ = kStarted;
   if (!client_)
@@ -170,30 +204,64 @@ OutputDevice* WebAudioSourceProviderImpl::GetOutputDevice() {
   return sink_->GetOutputDevice();
 }
 
-void WebAudioSourceProviderImpl::Initialize(
-    const AudioParameters& params,
-    RenderCallback* renderer) {
+void WebAudioSourceProviderImpl::Initialize(const AudioParameters& params,
+                                            RenderCallback* renderer) {
   base::AutoLock auto_lock(sink_lock_);
-  renderer_ = renderer;
-
   DCHECK_EQ(state_, kStopped);
-  sink_->Initialize(params, renderer);
 
-  // Keep track of the format in case the client hasn't yet been set.
-  channels_ = params.channels();
-  sample_rate_ = params.sample_rate();
+  tee_filter_ = make_scoped_ptr(
+      new TeeFilter(renderer, params.channels(), params.sample_rate()));
+
+  sink_->Initialize(params, tee_filter_.get());
 
   if (!set_format_cb_.is_null())
     base::ResetAndReturn(&set_format_cb_).Run();
 }
 
+void WebAudioSourceProviderImpl::SetCopyAudioCallback(
+    const CopyAudioCB& callback) {
+  DCHECK(!callback.is_null());
+  DCHECK(tee_filter_);
+  tee_filter_->set_copy_audio_bus_callback(callback);
+}
+
+void WebAudioSourceProviderImpl::ClearCopyAudioCallback() {
+  DCHECK(tee_filter_);
+  tee_filter_->set_copy_audio_bus_callback(CopyAudioCB());
+}
+
 void WebAudioSourceProviderImpl::OnSetFormat() {
   base::AutoLock auto_lock(sink_lock_);
   if (!client_)
     return;
 
   // Inform Blink about the audio stream format.
-  client_->setFormat(channels_, sample_rate_);
+  client_->setFormat(tee_filter_->channels(), tee_filter_->sample_rate());
+}
+
+int WebAudioSourceProviderImpl::RenderForTesting(AudioBus* audio_bus) {
+  return tee_filter_->Render(audio_bus, 0, 0);
+}
+
+int WebAudioSourceProviderImpl::TeeFilter::Render(AudioBus* audio_bus,
+                                                  uint32_t delay_milliseconds,
+                                                  uint32_t frames_skipped) {
+  const int num_rendered_frames =
+      renderer_->Render(audio_bus, delay_milliseconds, frames_skipped);
+
+  if (!copy_audio_bus_callback_.is_null()) {
+    scoped_ptr<AudioBus> bus_copy =
+        AudioBus::Create(audio_bus->channels(), audio_bus->frames());
+    audio_bus->CopyTo(bus_copy.get());
+    copy_audio_bus_callback_.Run(std::move(bus_copy), delay_milliseconds,
+                                 sample_rate_);
+  }
+
+  return num_rendered_frames;
+}
+
+void WebAudioSourceProviderImpl::TeeFilter::OnRenderError() {
+  renderer_->OnRenderError();
 }
 
 }  // namespace media