content/browser/renderer_host/media/web_contents_video_capture_device.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5 // Implementation notes: This needs to work on a variety of hardware
   6 // configurations where the speed of the CPU and GPU greatly affect overall
   7 // performance. Spanning several threads, the process of capturing has been
   8 // split up into four conceptual stages:
   9 //
  10 //   1. Reserve Buffer: Before a frame can be captured, a slot in the client's
  11 //      shared-memory IPC buffer is reserved. There are only a few of these;
  12 //      when they run out, it indicates that the downstream client -- likely a
  13 //      video encoder -- is the performance bottleneck, and that the rate of
  14 //      frame capture should be throttled back.
  15 //
  16 //   2. Capture: A bitmap is snapshotted/copied from the RenderView's backing
  17 //      store. This is initiated on the UI BrowserThread, and often occurs
  18 //      asynchronously. Where supported, the GPU scales and color converts
  19 //      frames to our desired size, and the readback happens directly into the
  20 //      shared-memory buffer. But this is not always possible, particularly when
  21 //      accelerated compositing is disabled.
  22 //
  23 //   3. Render (if needed): If the web contents cannot be captured directly into
  24 //      our target size and color format, scaling and colorspace conversion must
  25 //      be done on the CPU. A dedicated thread is used for this operation, to
  26 //      avoid blocking the UI thread. The Render stage always reads from a
  27 //      bitmap returned by Capture, and writes into the reserved slot in the
  28 //      shared-memory buffer.
  29 //
  30 //   4. Deliver: The rendered video frame is returned to the client (which
  31 //      implements the VideoCaptureDevice::Client interface). Because all
  32 //      paths have written the frame into the IPC buffer, this step should
  33 //      never need to do an additional copy of the pixel data.
  34 //
  35 // In the best-performing case, the Render step is bypassed: Capture produces
  36 // ready-to-Deliver frames. But when accelerated readback is not possible, the
  37 // system is designed so that Capture and Render may run concurrently. A timing
  38 // diagram helps illustrate this point (@30 FPS):
  39 //
  40 //    Time: 0ms                 33ms                 66ms                 99ms
  41 // thread1: |-Capture-f1------v |-Capture-f2------v  |-Capture-f3----v    |-Capt
  42 // thread2:                   |-Render-f1-----v   |-Render-f2-----v  |-Render-f3
  43 //
  44 // In the above example, both capturing and rendering *each* take almost the
  45 // full 33 ms available between frames, yet we see that the required throughput
  46 // is obtained.
  47 //
  48 // Turning on verbose logging will cause the effective frame rate to be logged
  49 // at 5-second intervals.
  50
  51 #include "content/browser/renderer_host/media/web_contents_video_capture_device.h"
  52
  53 #include "base/basictypes.h"
  54 #include "base/bind.h"
  55 #include "base/callback_helpers.h"
  56 #include "base/logging.h"
  57 #include "base/memory/scoped_ptr.h"
  58 #include "base/message_loop/message_loop_proxy.h"
  59 #include "base/metrics/histogram.h"
  60 #include "base/sequenced_task_runner.h"
  61 #include "base/threading/thread.h"
  62 #include "base/threading/thread_checker.h"
  63 #include "base/time/time.h"
  64 #include "content/browser/renderer_host/media/video_capture_device_impl.h"
  65 #include "content/browser/renderer_host/media/video_capture_oracle.h"
  66 #include "content/browser/renderer_host/media/web_contents_capture_util.h"
  67 #include "content/browser/renderer_host/render_widget_host_impl.h"
  68 #include "content/browser/web_contents/web_contents_impl.h"
  69 #include "content/port/browser/render_widget_host_view_frame_subscriber.h"
  70 #include "content/port/browser/render_widget_host_view_port.h"
  71 #include "content/public/browser/browser_thread.h"
  72 #include "content/public/browser/notification_source.h"
  73 #include "content/public/browser/notification_types.h"
  74 #include "content/public/browser/render_view_host.h"
  75 #include "content/public/browser/render_widget_host_view.h"
  76 #include "content/public/browser/web_contents_observer.h"
  77 #include "media/base/video_util.h"
  78 #include "media/video/capture/video_capture_types.h"
  79 #include "skia/ext/image_operations.h"
  80 #include "third_party/skia/include/core/SkBitmap.h"
  81 #include "third_party/skia/include/core/SkColor.h"
  82
  83 namespace content {
  84
  85 namespace {
  86
  87 // Compute a letterbox region, aligned to even coordinates.
  88 gfx::Rect ComputeYV12LetterboxRegion(const gfx::Size& frame_size,
  89                                      const gfx::Size& content_size) {
  90
  91   gfx::Rect result = media::ComputeLetterboxRegion(gfx::Rect(frame_size),
  92                                                    content_size);
  93
  94   result.set_x(MakeEven(result.x()));
  95   result.set_y(MakeEven(result.y()));
  96   result.set_width(std::max(kMinFrameWidth, MakeEven(result.width())));
  97   result.set_height(std::max(kMinFrameHeight, MakeEven(result.height())));
  98
  99   return result;
 100 }
 101
 102 // Wrapper function to invoke ThreadSafeCaptureOracle::CaptureFrameCallback, is
 103 // compatible with RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback.
 104 void InvokeCaptureFrameCallback(
 105     const ThreadSafeCaptureOracle::CaptureFrameCallback& capture_frame_cb,
 106     base::TimeTicks timestamp,
 107     bool frame_captured) {
 108   capture_frame_cb.Run(timestamp, frame_captured);
 109 }
 110
 111 // FrameSubscriber is a proxy to the ThreadSafeCaptureOracle that's compatible
 112 // with RenderWidgetHostViewFrameSubscriber. We create one per event type.
 113 class FrameSubscriber : public RenderWidgetHostViewFrameSubscriber {
 114  public:
 115   FrameSubscriber(VideoCaptureOracle::Event event_type,
 116                   const scoped_refptr<ThreadSafeCaptureOracle>& oracle)
 117       : event_type_(event_type),
 118         oracle_proxy_(oracle) {}
 119
 120   virtual bool ShouldCaptureFrame(
 121       base::TimeTicks present_time,
 122       scoped_refptr<media::VideoFrame>* storage,
 123       RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback*
 124           deliver_frame_cb) OVERRIDE;
 125
 126  private:
 127   const VideoCaptureOracle::Event event_type_;
 128   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
 129 };
 130
 131 // ContentCaptureSubscription is the relationship between a RenderWidgetHost
 132 // whose content is updating, a subscriber that is deciding which of these
 133 // updates to capture (and where to deliver them to), and a callback that
 134 // knows how to do the capture and prepare the result for delivery.
 135 //
 136 // In practice, this means (a) installing a RenderWidgetHostFrameSubscriber in
 137 // the RenderWidgetHostView, to process updates that occur via accelerated
 138 // compositing, (b) installing itself as an observer of updates to the
 139 // RenderWidgetHost's backing store, to hook updates that occur via software
 140 // rendering, and (c) running a timer to possibly initiate non-event-driven
 141 // captures that the subscriber might request.
 142 //
 143 // All of this happens on the UI thread, although the
 144 // RenderWidgetHostViewFrameSubscriber we install may be dispatching updates
 145 // autonomously on some other thread.
 146 class ContentCaptureSubscription : public content::NotificationObserver {
 147  public:
 148   typedef base::Callback<
 149       void(const base::TimeTicks&,
 150            const scoped_refptr<media::VideoFrame>&,
 151            const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&)>
 152       CaptureCallback;
 153
 154   // Create a subscription. Whenever a manual capture is required, the
 155   // subscription will invoke |capture_callback| on the UI thread to do the
 156   // work.
 157   ContentCaptureSubscription(
 158       const RenderWidgetHost& source,
 159       const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 160       const CaptureCallback& capture_callback);
 161   virtual ~ContentCaptureSubscription();
 162
 163   // content::NotificationObserver implementation.
 164   virtual void Observe(int type,
 165                        const content::NotificationSource& source,
 166                        const content::NotificationDetails& details) OVERRIDE;
 167
 168  private:
 169   void OnTimer();
 170
 171   const int render_process_id_;
 172   const int render_view_id_;
 173
 174   FrameSubscriber paint_subscriber_;
 175   FrameSubscriber timer_subscriber_;
 176   content::NotificationRegistrar registrar_;
 177   CaptureCallback capture_callback_;
 178   base::Timer timer_;
 179
 180   DISALLOW_COPY_AND_ASSIGN(ContentCaptureSubscription);
 181 };
 182
 183 // Render the SkBitmap |input| into the given VideoFrame buffer |output|, then
 184 // invoke |done_cb| to indicate success or failure. |input| is expected to be
 185 // ARGB. |output| must be YV12 or I420. Colorspace conversion is always done.
 186 // Scaling and letterboxing will be done as needed.
 187 //
 188 // This software implementation should be used only when GPU acceleration of
 189 // these activities is not possible. This operation may be expensive (tens to
 190 // hundreds of milliseconds), so the caller should ensure that it runs on a
 191 // thread where such a pause would cause UI jank.
 192 void RenderVideoFrame(const SkBitmap& input,
 193                       const scoped_refptr<media::VideoFrame>& output,
 194                       const base::Callback<void(bool)>& done_cb);
 195
 196 // Keeps track of the RenderView to be sourced, and executes copying of the
 197 // backing store on the UI BrowserThread.
 198 //
 199 // TODO(nick): It would be nice to merge this with WebContentsTracker, but its
 200 // implementation is currently asynchronous -- in our case, the "rvh changed"
 201 // notification would get posted back to the UI thread and processed later, and
 202 // this seems disadvantageous.
 203 class WebContentsCaptureMachine
 204     : public VideoCaptureMachine,
 205       public WebContentsObserver,
 206       public base::SupportsWeakPtr<WebContentsCaptureMachine> {
 207  public:
 208   WebContentsCaptureMachine(int render_process_id, int render_view_id);
 209   virtual ~WebContentsCaptureMachine();
 210
 211   // VideoCaptureMachine overrides.
 212   virtual bool Start(
 213       const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy) OVERRIDE;
 214   virtual void Stop() OVERRIDE;
 215
 216   // Starts a copy from the backing store or the composited surface. Must be run
 217   // on the UI BrowserThread. |deliver_frame_cb| will be run when the operation
 218   // completes. The copy will occur to |target|.
 219   //
 220   // This may be used as a ContentCaptureSubscription::CaptureCallback.
 221   void Capture(const base::TimeTicks& start_time,
 222                const scoped_refptr<media::VideoFrame>& target,
 223                const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 224                    deliver_frame_cb);
 225
 226   // content::WebContentsObserver implementation.
 227   virtual void DidShowFullscreenWidget(int routing_id) OVERRIDE {
 228     fullscreen_widget_id_ = routing_id;
 229     RenewFrameSubscription();
 230   }
 231
 232   virtual void DidDestroyFullscreenWidget(int routing_id) OVERRIDE {
 233     DCHECK_EQ(fullscreen_widget_id_, routing_id);
 234     fullscreen_widget_id_ = MSG_ROUTING_NONE;
 235     RenewFrameSubscription();
 236   }
 237
 238   virtual void RenderViewReady() OVERRIDE {
 239     RenewFrameSubscription();
 240   }
 241
 242   virtual void AboutToNavigateRenderView(RenderViewHost* rvh) OVERRIDE {
 243     RenewFrameSubscription();
 244   }
 245
 246   virtual void DidNavigateMainFrame(
 247       const LoadCommittedDetails& details,
 248       const FrameNavigateParams& params) OVERRIDE {
 249     RenewFrameSubscription();
 250   }
 251
 252   virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
 253
 254  private:
 255   // Starts observing the web contents, returning false if lookup fails.
 256   bool StartObservingWebContents();
 257
 258   // Helper function to determine the view that we are currently tracking.
 259   RenderWidgetHost* GetTarget();
 260
 261   // Response callback for RenderWidgetHost::CopyFromBackingStore().
 262   void DidCopyFromBackingStore(
 263       const base::TimeTicks& start_time,
 264       const scoped_refptr<media::VideoFrame>& target,
 265       const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 266           deliver_frame_cb,
 267       bool success,
 268       const SkBitmap& bitmap);
 269
 270   // Response callback for RWHVP::CopyFromCompositingSurfaceToVideoFrame().
 271   void DidCopyFromCompositingSurfaceToVideoFrame(
 272       const base::TimeTicks& start_time,
 273       const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 274           deliver_frame_cb,
 275       bool success);
 276
 277   // Remove the old subscription, and start a new one. This should be called
 278   // after any change to the WebContents that affects the RenderWidgetHost or
 279   // attached views.
 280   void RenewFrameSubscription();
 281
 282   // Parameters saved in constructor.
 283   const int initial_render_process_id_;
 284   const int initial_render_view_id_;
 285
 286   // A dedicated worker thread on which SkBitmap->VideoFrame conversion will
 287   // occur. Only used when this activity cannot be done on the GPU.
 288   base::Thread render_thread_;
 289
 290   // Makes all the decisions about which frames to copy, and how.
 291   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
 292
 293   // Routing ID of any active fullscreen render widget or MSG_ROUTING_NONE
 294   // otherwise.
 295   int fullscreen_widget_id_;
 296
 297   // Last known RenderView size.
 298   gfx::Size last_view_size_;
 299
 300   // Responsible for forwarding events from the active RenderWidgetHost to the
 301   // oracle, and initiating captures accordingly.
 302   scoped_ptr<ContentCaptureSubscription> subscription_;
 303
 304   DISALLOW_COPY_AND_ASSIGN(WebContentsCaptureMachine);
 305 };
 306
 307 // Responsible for logging the effective frame rate.
 308 // TODO(nick): Make this compatible with the push model and hook it back up.
 309 class VideoFrameDeliveryLog {
 310  public:
 311   VideoFrameDeliveryLog();
 312
 313   // Treat |frame_number| as having been delivered, and update the
 314   // frame rate statistics accordingly.
 315   void ChronicleFrameDelivery(int frame_number);
 316
 317  private:
 318   // The following keep track of and log the effective frame rate whenever
 319   // verbose logging is turned on.
 320   base::TimeTicks last_frame_rate_log_time_;
 321   int count_frames_rendered_;
 322   int last_frame_number_;
 323
 324   DISALLOW_COPY_AND_ASSIGN(VideoFrameDeliveryLog);
 325 };
 326
 327 bool FrameSubscriber::ShouldCaptureFrame(
 328     base::TimeTicks present_time,
 329     scoped_refptr<media::VideoFrame>* storage,
 330     DeliverFrameCallback* deliver_frame_cb) {
 331   TRACE_EVENT1("mirroring", "FrameSubscriber::ShouldCaptureFrame",
 332                "instance", this);
 333
 334   ThreadSafeCaptureOracle::CaptureFrameCallback capture_frame_cb;
 335   bool oracle_decision = oracle_proxy_->ObserveEventAndDecideCapture(
 336       event_type_, present_time, storage, &capture_frame_cb);
 337
 338   *deliver_frame_cb = base::Bind(&InvokeCaptureFrameCallback, capture_frame_cb);
 339   return oracle_decision;
 340 }
 341
 342 ContentCaptureSubscription::ContentCaptureSubscription(
 343     const RenderWidgetHost& source,
 344     const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 345     const CaptureCallback& capture_callback)
 346     : render_process_id_(source.GetProcess()->GetID()),
 347       render_view_id_(source.GetRoutingID()),
 348       paint_subscriber_(VideoCaptureOracle::kSoftwarePaint, oracle_proxy),
 349       timer_subscriber_(VideoCaptureOracle::kTimerPoll, oracle_proxy),
 350       capture_callback_(capture_callback),
 351       timer_(true, true) {
 352   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 353
 354   RenderWidgetHostViewPort* view =
 355       RenderWidgetHostViewPort::FromRWHV(source.GetView());
 356
 357   // Subscribe to accelerated presents. These will be serviced directly by the
 358   // oracle.
 359   if (view && kAcceleratedSubscriberIsSupported) {
 360     scoped_ptr<RenderWidgetHostViewFrameSubscriber> subscriber(
 361         new FrameSubscriber(VideoCaptureOracle::kCompositorUpdate,
 362             oracle_proxy));
 363     view->BeginFrameSubscription(subscriber.Pass());
 364   }
 365
 366   // Subscribe to software paint events. This instance will service these by
 367   // reflecting them back to the WebContentsCaptureMachine via
 368   // |capture_callback|.
 369   registrar_.Add(
 370       this, content::NOTIFICATION_RENDER_WIDGET_HOST_DID_UPDATE_BACKING_STORE,
 371       Source<RenderWidgetHost>(&source));
 372
 373   // Subscribe to timer events. This instance will service these as well.
 374   timer_.Start(FROM_HERE, oracle_proxy->capture_period(),
 375                base::Bind(&ContentCaptureSubscription::OnTimer,
 376                           base::Unretained(this)));
 377 }
 378
 379 ContentCaptureSubscription::~ContentCaptureSubscription() {
 380   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 381   if (kAcceleratedSubscriberIsSupported) {
 382     RenderViewHost* source = RenderViewHost::FromID(render_process_id_,
 383                                                     render_view_id_);
 384     if (source) {
 385       RenderWidgetHostViewPort* view =
 386           RenderWidgetHostViewPort::FromRWHV(source->GetView());
 387       if (view)
 388         view->EndFrameSubscription();
 389     }
 390   }
 391 }
 392
 393 void ContentCaptureSubscription::Observe(
 394     int type,
 395     const content::NotificationSource& source,
 396     const content::NotificationDetails& details) {
 397   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 398   DCHECK_EQ(NOTIFICATION_RENDER_WIDGET_HOST_DID_UPDATE_BACKING_STORE, type);
 399
 400   RenderWidgetHostImpl* rwh =
 401       RenderWidgetHostImpl::From(Source<RenderWidgetHost>(source).ptr());
 402
 403   // This message occurs on window resizes and visibility changes even when
 404   // accelerated compositing is active, so we need to filter out these cases.
 405   if (!rwh || !rwh->GetView() || (rwh->is_accelerated_compositing_active() &&
 406                                   rwh->GetView()->IsSurfaceAvailableForCopy()))
 407     return;
 408
 409   TRACE_EVENT1("mirroring", "ContentCaptureSubscription::Observe",
 410                "instance", this);
 411
 412   base::Closure copy_done_callback;
 413   scoped_refptr<media::VideoFrame> frame;
 414   RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback deliver_frame_cb;
 415   const base::TimeTicks start_time = base::TimeTicks::Now();
 416   if (paint_subscriber_.ShouldCaptureFrame(start_time,
 417                                            &frame,
 418                                            &deliver_frame_cb)) {
 419     // This message happens just before paint. If we post a task to do the copy,
 420     // it should run soon after the paint.
 421     BrowserThread::PostTask(
 422         BrowserThread::UI, FROM_HERE,
 423         base::Bind(capture_callback_, start_time, frame, deliver_frame_cb));
 424   }
 425 }
 426
 427 void ContentCaptureSubscription::OnTimer() {
 428   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 429   TRACE_EVENT0("mirroring", "ContentCaptureSubscription::OnTimer");
 430
 431   scoped_refptr<media::VideoFrame> frame;
 432   RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback deliver_frame_cb;
 433
 434   const base::TimeTicks start_time = base::TimeTicks::Now();
 435   if (timer_subscriber_.ShouldCaptureFrame(start_time,
 436                                            &frame,
 437                                            &deliver_frame_cb)) {
 438     capture_callback_.Run(start_time, frame, deliver_frame_cb);
 439   }
 440 }
 441
 442 void RenderVideoFrame(const SkBitmap& input,
 443                       const scoped_refptr<media::VideoFrame>& output,
 444                       const base::Callback<void(bool)>& done_cb) {
 445   base::ScopedClosureRunner failure_handler(base::Bind(done_cb, false));
 446
 447   SkAutoLockPixels locker(input);
 448
 449   // Sanity-check the captured bitmap.
 450   if (input.empty() ||
 451       !input.readyToDraw() ||
 452       input.config() != SkBitmap::kARGB_8888_Config ||
 453       input.width() < 2 || input.height() < 2) {
 454     DVLOG(1) << "input unacceptable (size="
 455              << input.getSize()
 456              << ", ready=" << input.readyToDraw()
 457              << ", config=" << input.config() << ')';
 458     return;
 459   }
 460
 461   // Sanity-check the output buffer.
 462   if (output->format() != media::VideoFrame::I420) {
 463     NOTREACHED();
 464     return;
 465   }
 466
 467   // Calculate the width and height of the content region in the |output|, based
 468   // on the aspect ratio of |input|.
 469   gfx::Rect region_in_frame = ComputeYV12LetterboxRegion(
 470       output->coded_size(), gfx::Size(input.width(), input.height()));
 471
 472   // Scale the bitmap to the required size, if necessary.
 473   SkBitmap scaled_bitmap;
 474   if (input.width() != region_in_frame.width() ||
 475       input.height() != region_in_frame.height()) {
 476
 477     skia::ImageOperations::ResizeMethod method;
 478     if (input.width() < region_in_frame.width() ||
 479         input.height() < region_in_frame.height()) {
 480       // Avoid box filtering when magnifying, because it's actually
 481       // nearest-neighbor.
 482       method = skia::ImageOperations::RESIZE_HAMMING1;
 483     } else {
 484       method = skia::ImageOperations::RESIZE_BOX;
 485     }
 486
 487     TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", output.get(), "Scale");
 488     scaled_bitmap = skia::ImageOperations::Resize(input, method,
 489                                                   region_in_frame.width(),
 490                                                   region_in_frame.height());
 491   } else {
 492     scaled_bitmap = input;
 493   }
 494
 495   TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", output.get(), "YUV");
 496   {
 497     SkAutoLockPixels scaled_bitmap_locker(scaled_bitmap);
 498
 499     media::CopyRGBToVideoFrame(
 500         reinterpret_cast<uint8*>(scaled_bitmap.getPixels()),
 501         scaled_bitmap.rowBytes(),
 502         region_in_frame,
 503         output.get());
 504   }
 505
 506   // The result is now ready.
 507   ignore_result(failure_handler.Release());
 508   done_cb.Run(true);
 509 }
 510
 511 VideoFrameDeliveryLog::VideoFrameDeliveryLog()
 512     : last_frame_rate_log_time_(),
 513       count_frames_rendered_(0),
 514       last_frame_number_(0) {
 515 }
 516
 517 void VideoFrameDeliveryLog::ChronicleFrameDelivery(int frame_number) {
 518   // Log frame rate, if verbose logging is turned on.
 519   static const base::TimeDelta kFrameRateLogInterval =
 520       base::TimeDelta::FromSeconds(10);
 521   const base::TimeTicks now = base::TimeTicks::Now();
 522   if (last_frame_rate_log_time_.is_null()) {
 523     last_frame_rate_log_time_ = now;
 524     count_frames_rendered_ = 0;
 525     last_frame_number_ = frame_number;
 526   } else {
 527     ++count_frames_rendered_;
 528     const base::TimeDelta elapsed = now - last_frame_rate_log_time_;
 529     if (elapsed >= kFrameRateLogInterval) {
 530       const double measured_fps =
 531           count_frames_rendered_ / elapsed.InSecondsF();
 532       const int frames_elapsed = frame_number - last_frame_number_;
 533       const int count_frames_dropped = frames_elapsed - count_frames_rendered_;
 534       DCHECK_LE(0, count_frames_dropped);
 535       UMA_HISTOGRAM_PERCENTAGE(
 536           "TabCapture.FrameDropPercentage",
 537           (count_frames_dropped * 100 + frames_elapsed / 2) / frames_elapsed);
 538       UMA_HISTOGRAM_COUNTS(
 539           "TabCapture.FrameRate",
 540           static_cast<int>(measured_fps));
 541       VLOG(1) << "Current measured frame rate for "
 542               << "WebContentsVideoCaptureDevice is " << measured_fps << " FPS.";
 543       last_frame_rate_log_time_ = now;
 544       count_frames_rendered_ = 0;
 545       last_frame_number_ = frame_number;
 546     }
 547   }
 548 }
 549
 550 WebContentsCaptureMachine::WebContentsCaptureMachine(int render_process_id,
 551                                                      int render_view_id)
 552     : initial_render_process_id_(render_process_id),
 553       initial_render_view_id_(render_view_id),
 554       render_thread_("WebContentsVideo_RenderThread"),
 555       fullscreen_widget_id_(MSG_ROUTING_NONE) {}
 556
 557 WebContentsCaptureMachine::~WebContentsCaptureMachine() {}
 558
 559 bool WebContentsCaptureMachine::Start(
 560     const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy) {
 561   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 562   DCHECK(!started_);
 563
 564   DCHECK(oracle_proxy.get());
 565   oracle_proxy_ = oracle_proxy;
 566
 567   if (!render_thread_.Start()) {
 568     DVLOG(1) << "Failed to spawn render thread.";
 569     return false;
 570   }
 571
 572   if (!StartObservingWebContents())
 573     return false;
 574
 575   started_ = true;
 576   return true;
 577 }
 578
 579 void WebContentsCaptureMachine::Stop() {
 580   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 581   subscription_.reset();
 582   if (web_contents()) {
 583     web_contents()->DecrementCapturerCount();
 584     Observe(NULL);
 585   }
 586   render_thread_.Stop();
 587   started_ = false;
 588 }
 589
 590 void WebContentsCaptureMachine::Capture(
 591     const base::TimeTicks& start_time,
 592     const scoped_refptr<media::VideoFrame>& target,
 593     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 594         deliver_frame_cb) {
 595   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 596
 597   RenderWidgetHost* rwh = GetTarget();
 598   RenderWidgetHostViewPort* view =
 599       rwh ? RenderWidgetHostViewPort::FromRWHV(rwh->GetView()) : NULL;
 600   if (!view || !rwh) {
 601     deliver_frame_cb.Run(base::TimeTicks(), false);
 602     return;
 603   }
 604
 605   gfx::Size video_size = target->coded_size();
 606   gfx::Size view_size = view->GetViewBounds().size();
 607   gfx::Size fitted_size;
 608   if (!view_size.IsEmpty()) {
 609     fitted_size = ComputeYV12LetterboxRegion(video_size, view_size).size();
 610   }
 611   if (view_size != last_view_size_) {
 612     last_view_size_ = view_size;
 613
 614     // Measure the number of kilopixels.
 615     UMA_HISTOGRAM_COUNTS_10000(
 616         "TabCapture.ViewChangeKiloPixels",
 617         view_size.width() * view_size.height() / 1024);
 618   }
 619
 620   if (!view->IsSurfaceAvailableForCopy()) {
 621     // Fallback to the more expensive renderer-side copy if the surface and
 622     // backing store are not accessible.
 623     rwh->GetSnapshotFromRenderer(
 624         gfx::Rect(),
 625         base::Bind(&WebContentsCaptureMachine::DidCopyFromBackingStore,
 626                    this->AsWeakPtr(), start_time, target, deliver_frame_cb));
 627   } else if (view->CanCopyToVideoFrame()) {
 628     view->CopyFromCompositingSurfaceToVideoFrame(
 629         gfx::Rect(view_size),
 630         target,
 631         base::Bind(&WebContentsCaptureMachine::
 632                         DidCopyFromCompositingSurfaceToVideoFrame,
 633                    this->AsWeakPtr(), start_time, deliver_frame_cb));
 634   } else {
 635     rwh->CopyFromBackingStore(
 636         gfx::Rect(),
 637         fitted_size,  // Size here is a request not always honored.
 638         base::Bind(&WebContentsCaptureMachine::DidCopyFromBackingStore,
 639                    this->AsWeakPtr(), start_time, target, deliver_frame_cb));
 640   }
 641 }
 642
 643 bool WebContentsCaptureMachine::StartObservingWebContents() {
 644   // Look-up the RenderViewHost and, from that, the WebContents that wraps it.
 645   // If successful, begin observing the WebContents instance.
 646   //
 647   // Why this can be unsuccessful: The request for mirroring originates in a
 648   // render process, and this request is based on the current RenderView
 649   // associated with a tab.  However, by the time we get up-and-running here,
 650   // there have been multiple back-and-forth IPCs between processes, as well as
 651   // a bit of indirection across threads.  It's easily possible that, in the
 652   // meantime, the original RenderView may have gone away.
 653   RenderViewHost* const rvh =
 654       RenderViewHost::FromID(initial_render_process_id_,
 655                              initial_render_view_id_);
 656   DVLOG_IF(1, !rvh) << "RenderViewHost::FromID("
 657                     << initial_render_process_id_ << ", "
 658                     << initial_render_view_id_ << ") returned NULL.";
 659   Observe(rvh ? WebContents::FromRenderViewHost(rvh) : NULL);
 660
 661   WebContentsImpl* contents = static_cast<WebContentsImpl*>(web_contents());
 662   if (contents) {
 663     contents->IncrementCapturerCount();
 664     fullscreen_widget_id_ = contents->GetFullscreenWidgetRoutingID();
 665     RenewFrameSubscription();
 666     return true;
 667   }
 668
 669   DVLOG(1) << "WebContents::FromRenderViewHost(" << rvh << ") returned NULL.";
 670   return false;
 671 }
 672
 673 void WebContentsCaptureMachine::WebContentsDestroyed(
 674     WebContents* web_contents) {
 675   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 676
 677   subscription_.reset();
 678   web_contents->DecrementCapturerCount();
 679   oracle_proxy_->ReportError();
 680 }
 681
 682 RenderWidgetHost* WebContentsCaptureMachine::GetTarget() {
 683   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 684   if (!web_contents())
 685     return NULL;
 686
 687   RenderWidgetHost* rwh = NULL;
 688   if (fullscreen_widget_id_ != MSG_ROUTING_NONE) {
 689     RenderProcessHost* process = web_contents()->GetRenderProcessHost();
 690     if (process)
 691       rwh = RenderWidgetHost::FromID(process->GetID(), fullscreen_widget_id_);
 692   } else {
 693     rwh = web_contents()->GetRenderViewHost();
 694   }
 695
 696   return rwh;
 697 }
 698
 699 void WebContentsCaptureMachine::DidCopyFromBackingStore(
 700     const base::TimeTicks& start_time,
 701     const scoped_refptr<media::VideoFrame>& target,
 702     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 703         deliver_frame_cb,
 704     bool success,
 705     const SkBitmap& bitmap) {
 706   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 707
 708   base::TimeTicks now = base::TimeTicks::Now();
 709   if (success) {
 710     UMA_HISTOGRAM_TIMES("TabCapture.CopyTimeBitmap", now - start_time);
 711     TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", target.get(),
 712                                  "Render");
 713     render_thread_.message_loop_proxy()->PostTask(FROM_HERE, base::Bind(
 714         &RenderVideoFrame, bitmap, target,
 715         base::Bind(deliver_frame_cb, start_time)));
 716   } else {
 717     // Capture can fail due to transient issues, so just skip this frame.
 718     DVLOG(1) << "CopyFromBackingStore failed; skipping frame.";
 719     deliver_frame_cb.Run(start_time, false);
 720   }
 721 }
 722
 723 void WebContentsCaptureMachine::DidCopyFromCompositingSurfaceToVideoFrame(
 724     const base::TimeTicks& start_time,
 725     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 726         deliver_frame_cb,
 727     bool success) {
 728   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 729   base::TimeTicks now = base::TimeTicks::Now();
 730
 731   if (success) {
 732     UMA_HISTOGRAM_TIMES("TabCapture.CopyTimeVideoFrame", now - start_time);
 733   } else {
 734     // Capture can fail due to transient issues, so just skip this frame.
 735     DVLOG(1) << "CopyFromCompositingSurface failed; skipping frame.";
 736   }
 737   deliver_frame_cb.Run(start_time, success);
 738 }
 739
 740 void WebContentsCaptureMachine::RenewFrameSubscription() {
 741   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 742
 743   // Always destroy the old subscription before creating a new one.
 744   subscription_.reset();
 745
 746   RenderWidgetHost* rwh = GetTarget();
 747   if (!rwh || !rwh->GetView())
 748     return;
 749
 750   subscription_.reset(new ContentCaptureSubscription(*rwh, oracle_proxy_,
 751       base::Bind(&WebContentsCaptureMachine::Capture, this->AsWeakPtr())));
 752 }
 753
 754 }  // namespace
 755
 756 WebContentsVideoCaptureDevice::WebContentsVideoCaptureDevice(
 757     int render_process_id, int render_view_id)
 758     : impl_(new VideoCaptureDeviceImpl(scoped_ptr<VideoCaptureMachine>(
 759         new WebContentsCaptureMachine(render_process_id, render_view_id)))) {}
 760
 761 WebContentsVideoCaptureDevice::~WebContentsVideoCaptureDevice() {
 762   DVLOG(2) << "WebContentsVideoCaptureDevice@" << this << " destroying.";
 763 }
 764
 765 // static
 766 media::VideoCaptureDevice* WebContentsVideoCaptureDevice::Create(
 767     const std::string& device_id) {
 768   // Parse device_id into render_process_id and render_view_id.
 769   int render_process_id = -1;
 770   int render_view_id = -1;
 771   if (!WebContentsCaptureUtil::ExtractTabCaptureTarget(
 772            device_id, &render_process_id, &render_view_id)) {
 773     return NULL;
 774   }
 775
 776   return new WebContentsVideoCaptureDevice(render_process_id, render_view_id);
 777 }
 778
 779 void WebContentsVideoCaptureDevice::AllocateAndStart(
 780     const media::VideoCaptureParams& params,
 781     scoped_ptr<Client> client) {
 782   DVLOG(1) << "Allocating " << params.requested_format.frame_size.ToString();
 783   impl_->AllocateAndStart(params, client.Pass());
 784 }
 785
 786 void WebContentsVideoCaptureDevice::StopAndDeAllocate() {
 787   impl_->StopAndDeAllocate();
 788 }
 789
 790 }  // namespace content