Tab Audio Mirroring: WebContentsAudioInputStream is a new implementation which represents the lifet…

content/browser/renderer_host/media/web_contents_audio_input_stream.h

+// Copyright (c) 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.
+//
+// An AudioInputStream which provides a loop-back of all audio output generated
+// by the RenderView associated with a WebContents instance.  The single stream
+// of data is produced by format-converting and mixing all audio output from a
+// RenderView.  In other words, WebContentsAudioInputStream provides tab-level
+// audio mirroring.
+//
+// The implementation observes a WebContents instance (which represents a
+// browser tab) so that it can track the replacement of RenderViews due to
+// navigation, crash/reload, etc. events; and take appropriate actions to
+// provide a seamless, uninterrupted mirroring experience.
+
+#ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_AUDIO_INPUT_STREAM_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_AUDIO_INPUT_STREAM_H_
+
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "content/common/content_export.h"
+#include "media/audio/audio_io.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace media {
+class AudioParameters;
+class VirtualAudioInputStream;
+}
+
+namespace content {
+
+class AudioMirroringManager;
+class WebContentsTracker;
+
+class CONTENT_EXPORT WebContentsAudioInputStream
+    : NON_EXPORTED_BASE(public media::AudioInputStream) {
+ public:
+  virtual ~WebContentsAudioInputStream();

[tommi (sloooow) - chröme, 2013/01/14 14:06:48]

since the object deletes itself (as per the comment for Create()), should the
dtor be private?

[miu, 2013/01/14 21:53:03]

Done.

+
+  // media::AudioInputStream implementation
+  virtual bool Open() OVERRIDE;
+  virtual void Start(AudioInputCallback* callback) OVERRIDE;
+  virtual void Stop() OVERRIDE;
+  virtual void Close() OVERRIDE;
+  virtual double GetMaxVolume() OVERRIDE;
+  virtual void SetVolume(double volume) OVERRIDE;
+  virtual double GetVolume() OVERRIDE;
+  virtual void SetAutomaticGainControl(bool enabled) OVERRIDE;
+  virtual bool GetAutomaticGainControl() OVERRIDE;
+
+  // Create a new audio mirroring session.  |device_id| should be in the format
+  // accepted by WebContentsCaptureUtil::ExtractTabCaptureTarget().  The
+  // returned object self-destructs once Close() is called.
+  static WebContentsAudioInputStream* Create(
+      const std::string& device_id,
+      const media::AudioParameters& params,
+      base::MessageLoopProxy* message_loop);
+
+ private:
+  friend class WebContentsAudioInputStreamTest;
+
+  class Impl;
+
+  WebContentsAudioInputStream(
+      int render_process_id, int render_view_id,
+      base::MessageLoopProxy* message_loop,
+      AudioMirroringManager* mirroring_manager,
+      const scoped_refptr<WebContentsTracker>& tracker,
+      media::VirtualAudioInputStream* mixer_stream);
+
+  scoped_refptr<Impl> impl_;

[tommi (sloooow) - chröme, 2013/01/14 14:06:48]

add a comment about why we're using a pimpl.
(I'm assuming it's because of the Impl being ref counted?)

[miu, 2013/01/14 21:53:03]

Done.  (Comment added for the forward decl a few lines up.)

+
+  DISALLOW_COPY_AND_ASSIGN(WebContentsAudioInputStream);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_AUDIO_INPUT_STREAM_H_