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

media/blink/webaudiosourceprovider_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_
 #define MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_
 
 #include <stddef.h>
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
 #include "media/base/audio_renderer_sink.h"
 #include "media/blink/media_blink_export.h"
 #include "third_party/WebKit/public/platform/WebAudioSourceProvider.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 
 namespace blink {
 class WebAudioSourceProviderClient;
 }
 
 namespace media {
 
-// WebAudioSourceProviderImpl provides a bridge between classes:
-//     blink::WebAudioSourceProvider <---> AudioRendererSink
+// WebAudioSourceProviderImpl is either one of two things (but not both):
+// - a connection between a RestartableAudioRendererSink (the |sink_|) passed in
+//   constructor and an AudioRendererSink::RenderCallback passed on Initialize()
+//   by means of an internal AudioRendererSink::RenderCallback.
+// - a connection between the said AudioRendererSink::RenderCallback and a
+//   blink::WebAudioSourceProviderClient passed via setClient() (the |client_|),
+//   again using the internal AudioRendererSink::RenderCallback. Blink calls
+//   provideInput() periodically to fetch the appropriate data.
 //
-// WebAudioSourceProviderImpl wraps an existing audio sink that is used unless
-// WebKit has set a client via setClient(). While a client is set WebKit will
-// periodically call provideInput() to render a certain number of audio
-// sample-frames using the sink's RenderCallback to get the data.
+// In either case, the internal RenderCallback allows for delivering a copy of
+// the data if a listener is configured. WASPImpl is also a
+// RestartableAudioRendererSink itself in order to be controlled (Play(),
+// Pause() etc).
 //
 // All calls are protected by a lock.
 class MEDIA_BLINK_EXPORT WebAudioSourceProviderImpl
     : NON_EXPORTED_BASE(public blink::WebAudioSourceProvider),
       NON_EXPORTED_BASE(public RestartableAudioRendererSink) {
  public:
+  using CopyAudioCB = base::Callback<
+      void(scoped_ptr<AudioBus>, uint32_t delay_milliseconds, int sample_rate)>;
+
   explicit WebAudioSourceProviderImpl(
       const scoped_refptr<RestartableAudioRendererSink>& sink);
 
   // blink::WebAudioSourceProvider implementation.
   void setClient(blink::WebAudioSourceProviderClient* client) override;
   void provideInput(const blink::WebVector<float*>& audio_data,
                     size_t number_of_frames) override;
 
   // RestartableAudioRendererSink implementation.
   void Start() override;
   void Stop() override;
   void Play() override;
   void Pause() override;
   bool SetVolume(double volume) override;
   OutputDevice* GetOutputDevice() override;
   void Initialize(const AudioParameters& params,
                   RenderCallback* renderer) override;
 
- protected:
+  // These methods allow a client to get a copy of the rendered audio.
+  void RegisterCopyAudioCallback(const CopyAudioCB& callback);

[DaleCurtis, 2016/03/12 03:24:42]

s/Register/Set/ since there can only be one.

[mcasas, 2016/03/16 18:50:51]

Done.

+  void ClearCopyAudioCallback();
+
+ private:
+  friend class WebAudioSourceProviderImplTest;
   ~WebAudioSourceProviderImpl() override;
 
- private:
   // Calls setFormat() on |client_| from the Blink renderer thread.
   void OnSetFormat();
 
-  // Closure that posts a task to call OnSetFormat() on the renderer thread.
-  base::Closure set_format_cb_;
+  int RenderForTesting(AudioBus* audio_bus);
 
-  // Set to true when Initialize() is called.
-  int channels_;
-  int sample_rate_;
+  // Used to keep the volume across reconfigurations.
   double volume_;
 
   // Tracks the current playback state.
   enum PlaybackState { kStopped, kStarted, kPlaying };
   PlaybackState state_;
 
-  // Where audio comes from.
-  AudioRendererSink::RenderCallback* renderer_;
-
+  // Closure that calls OnSetFormat() on |client_| on the renderer thread.
+  base::Closure set_format_cb_;
   // When set via setClient() it overrides |sink_| for consuming audio.
   blink::WebAudioSourceProviderClient* client_;
 
   // Where audio ends up unless overridden by |client_|.
   base::Lock sink_lock_;
-  scoped_refptr<RestartableAudioRendererSink> sink_;
+  const scoped_refptr<RestartableAudioRendererSink> sink_;
   scoped_ptr<AudioBus> bus_wrapper_;
 
+  // An inner class acting as a T filter where actual data can be tapped.
+  class TeeFilter;
+  scoped_ptr<TeeFilter> tee_filter_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<WebAudioSourceProviderImpl> weak_factory_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(WebAudioSourceProviderImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_