"Buttery Smooth" Tab Capture.

content/browser/renderer_host/media/video_capture_controller.h

 // Copyright (c) 2012 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.
 //
 // VideoCaptureController is the glue between a VideoCaptureDevice and all
 // VideoCaptureHosts that have connected to it. A controller exists on behalf of
 // one (and only one) VideoCaptureDevice; both are owned by the
 // VideoCaptureManager.
 //
 // The VideoCaptureController is responsible for:
@@ skipping 48 matching lines @@
 #include "content/common/content_export.h"
 #include "content/common/media/video_capture.h"
 #include "media/video/capture/video_capture_device.h"
 #include "media/video/capture/video_capture_types.h"
 
 namespace content {
 class VideoCaptureBufferPool;
 
 class CONTENT_EXPORT VideoCaptureController {
  public:
-  VideoCaptureController();
+  // |max_buffers| is the maximum number of video frame buffers in-flight at any
+  // one time.  This value should be based on the logical capacity of the
+  // capture pipeline, and not on hardware performance.  For example, tab
+  // capture requires more buffers than webcam capture because the pipeline is
+  // longer (it includes read-backs pending in the GPU pipeline).
+  explicit VideoCaptureController(int max_buffers);
   virtual ~VideoCaptureController();
 
   base::WeakPtr<VideoCaptureController> GetWeakPtr();
 
   // Return a new VideoCaptureDeviceClient to forward capture events to this
   // instance.
   scoped_ptr<media::VideoCaptureDevice::Client> NewDeviceClient();
 
   // Start video capturing and try to use the resolution specified in |params|.
   // Buffers will be shared to the client as necessary. The client will continue
@@ skipping 69 matching lines @@
   media::VideoCaptureFormat video_capture_format_;
 
   base::WeakPtrFactory<VideoCaptureController> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureController);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_CONTROLLER_H_