"Buttery Smooth" Tab Capture.

content/browser/renderer_host/media/video_capture_manager.cc

 // 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.
 
 #include "content/browser/renderer_host/media/video_capture_manager.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 52 matching lines @@
       std::unique(formats->begin(), formats->end(), IsCaptureFormatSizeEqual);
   formats->erase(last, formats->end());
   // Mark all formats as I420, since this is what the renderer side will get
   // anyhow: the actual pixel format is decided at the device level.
   for (media::VideoCaptureFormats::iterator it = formats->begin();
        it != formats->end(); ++it) {
     it->pixel_format = media::PIXEL_FORMAT_I420;
   }
 }
 
+// The maximum number of buffers in the capture pipeline.  See
+// VideoCaptureController ctor comments for more details.
+const int kMaxNumberOfBuffers = 3;
+const int kMaxNumberOfBuffersForTabCapture = 5;
+
 }  // namespace
 
 namespace content {
 
 VideoCaptureManager::DeviceEntry::DeviceEntry(
     MediaStreamType stream_type,
     const std::string& id,
     scoped_ptr<VideoCaptureController> controller)
     : stream_type(stream_type),
       id(id),
@@ skipping 492 matching lines @@
 
   // Check if another session has already opened this device. If so, just
   // use that opened device.
   DeviceEntry* const existing_device =
       GetDeviceEntryForMediaStreamDevice(device_info);
   if (existing_device) {
     DCHECK_EQ(device_info.type, existing_device->stream_type);
     return existing_device;
   }
 
+  const int max_buffers = device_info.type == MEDIA_TAB_VIDEO_CAPTURE ?
+      kMaxNumberOfBuffersForTabCapture : kMaxNumberOfBuffers;
   scoped_ptr<VideoCaptureController> video_capture_controller(
-      new VideoCaptureController());
+      new VideoCaptureController(max_buffers));
   DeviceEntry* new_device = new DeviceEntry(device_info.type,
                                             device_info.id,
                                             video_capture_controller.Pass());
   devices_.insert(new_device);
   return new_device;
 }
 
 VideoCaptureManager::DeviceInfo* VideoCaptureManager::FindDeviceInfoById(
     const std::string& id,
     DeviceInfos& device_vector) {
@@ skipping 20 matching lines @@
 void VideoCaptureManager::SaveDesktopCaptureWindowIdOnDeviceThread(
     media::VideoCaptureSessionId session_id,
     gfx::NativeViewId window_id) {
   DCHECK(IsOnDeviceThread());
   DCHECK(notification_window_ids_.find(session_id) ==
          notification_window_ids_.end());
   notification_window_ids_[session_id] = window_id;
 }
 
 }  // namespace content