src/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/memory/weak_ptr.h"
  59 #include "base/message_loop/message_loop_proxy.h"
  60 #include "base/metrics/histogram.h"
  61 #include "base/sequenced_task_runner.h"
  62 #include "base/threading/thread.h"
  63 #include "base/threading/thread_checker.h"
  64 #include "base/time/time.h"
  65 #include "content/browser/renderer_host/media/content_video_capture_device_core.h"
  66 #include "content/browser/renderer_host/media/video_capture_oracle.h"
  67 #include "content/browser/renderer_host/media/web_contents_capture_util.h"
  68 #include "content/browser/renderer_host/render_widget_host_impl.h"
  69 #include "content/browser/web_contents/web_contents_impl.h"
  70 #include "content/port/browser/render_widget_host_view_frame_subscriber.h"
  71 #include "content/port/browser/render_widget_host_view_port.h"
  72 #include "content/public/browser/browser_thread.h"
  73 #include "content/public/browser/notification_source.h"
  74 #include "content/public/browser/notification_types.h"
  75 #include "content/public/browser/render_view_host.h"
  76 #include "content/public/browser/render_widget_host_view.h"
  77 #include "content/public/browser/web_contents_observer.h"
  78 #include "media/base/video_util.h"
  79 #include "media/video/capture/video_capture_types.h"
  80 #include "skia/ext/image_operations.h"
  81 #include "third_party/skia/include/core/SkBitmap.h"
  82 #include "third_party/skia/include/core/SkColor.h"
  83
  84 namespace content {
  85
  86 namespace {
  87
  88 // Compute a letterbox region, aligned to even coordinates.
  89 gfx::Rect ComputeYV12LetterboxRegion(const gfx::Size& frame_size,
  90                                      const gfx::Size& content_size) {
  91
  92   gfx::Rect result = media::ComputeLetterboxRegion(gfx::Rect(frame_size),
  93                                                    content_size);
  94
  95   result.set_x(MakeEven(result.x()));
  96   result.set_y(MakeEven(result.y()));
  97   result.set_width(std::max(kMinFrameWidth, MakeEven(result.width())));
  98   result.set_height(std::max(kMinFrameHeight, MakeEven(result.height())));
  99
 100   return result;
 101 }
 102
 103 // Wrapper function to invoke ThreadSafeCaptureOracle::CaptureFrameCallback, is
 104 // compatible with RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback.
 105 void InvokeCaptureFrameCallback(
 106     const ThreadSafeCaptureOracle::CaptureFrameCallback& capture_frame_cb,
 107     base::TimeTicks timestamp,
 108     bool frame_captured) {
 109   capture_frame_cb.Run(timestamp, frame_captured);
 110 }
 111
 112 void DeleteOnWorkerThread(scoped_ptr<base::Thread> render_thread,
 113                           const base::Closure& callback) {
 114   render_thread.reset();
 115
 116   // After thread join call the callback on UI thread.
 117   BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, callback);
 118 }
 119
 120 // FrameSubscriber is a proxy to the ThreadSafeCaptureOracle that's compatible
 121 // with RenderWidgetHostViewFrameSubscriber. We create one per event type.
 122 class FrameSubscriber : public RenderWidgetHostViewFrameSubscriber {
 123  public:
 124   FrameSubscriber(VideoCaptureOracle::Event event_type,
 125                   const scoped_refptr<ThreadSafeCaptureOracle>& oracle)
 126       : event_type_(event_type),
 127         oracle_proxy_(oracle) {}
 128
 129   virtual bool ShouldCaptureFrame(
 130       base::TimeTicks present_time,
 131       scoped_refptr<media::VideoFrame>* storage,
 132       RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback*
 133           deliver_frame_cb) OVERRIDE;
 134
 135  private:
 136   const VideoCaptureOracle::Event event_type_;
 137   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
 138 };
 139
 140 // ContentCaptureSubscription is the relationship between a RenderWidgetHost
 141 // whose content is updating, a subscriber that is deciding which of these
 142 // updates to capture (and where to deliver them to), and a callback that
 143 // knows how to do the capture and prepare the result for delivery.
 144 //
 145 // In practice, this means (a) installing a RenderWidgetHostFrameSubscriber in
 146 // the RenderWidgetHostView, to process updates that occur via accelerated
 147 // compositing, (b) installing itself as an observer of updates to the
 148 // RenderWidgetHost's backing store, to hook updates that occur via software
 149 // rendering, and (c) running a timer to possibly initiate non-event-driven
 150 // captures that the subscriber might request.
 151 //
 152 // All of this happens on the UI thread, although the
 153 // RenderWidgetHostViewFrameSubscriber we install may be dispatching updates
 154 // autonomously on some other thread.
 155 class ContentCaptureSubscription : public content::NotificationObserver {
 156  public:
 157   typedef base::Callback<
 158       void(const base::TimeTicks&,
 159            const scoped_refptr<media::VideoFrame>&,
 160            const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&)>
 161       CaptureCallback;
 162
 163   // Create a subscription. Whenever a manual capture is required, the
 164   // subscription will invoke |capture_callback| on the UI thread to do the
 165   // work.
 166   ContentCaptureSubscription(
 167       const RenderWidgetHost& source,
 168       const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 169       const CaptureCallback& capture_callback);
 170   virtual ~ContentCaptureSubscription();
 171
 172   // content::NotificationObserver implementation.
 173   virtual void Observe(int type,
 174                        const content::NotificationSource& source,
 175                        const content::NotificationDetails& details) OVERRIDE;
 176
 177  private:
 178   void OnTimer();
 179
 180   const int render_process_id_;
 181   const int render_view_id_;
 182
 183   FrameSubscriber paint_subscriber_;
 184   FrameSubscriber timer_subscriber_;
 185   content::NotificationRegistrar registrar_;
 186   CaptureCallback capture_callback_;
 187   base::Timer timer_;
 188
 189   DISALLOW_COPY_AND_ASSIGN(ContentCaptureSubscription);
 190 };
 191
 192 // Render the SkBitmap |input| into the given VideoFrame buffer |output|, then
 193 // invoke |done_cb| to indicate success or failure. |input| is expected to be
 194 // ARGB. |output| must be YV12 or I420. Colorspace conversion is always done.
 195 // Scaling and letterboxing will be done as needed.
 196 //
 197 // This software implementation should be used only when GPU acceleration of
 198 // these activities is not possible. This operation may be expensive (tens to
 199 // hundreds of milliseconds), so the caller should ensure that it runs on a
 200 // thread where such a pause would cause UI jank.
 201 void RenderVideoFrame(const SkBitmap& input,
 202                       const scoped_refptr<media::VideoFrame>& output,
 203                       const base::Callback<void(bool)>& done_cb);
 204
 205 // Keeps track of the RenderView to be sourced, and executes copying of the
 206 // backing store on the UI BrowserThread.
 207 //
 208 // TODO(nick): It would be nice to merge this with WebContentsTracker, but its
 209 // implementation is currently asynchronous -- in our case, the "rvh changed"
 210 // notification would get posted back to the UI thread and processed later, and
 211 // this seems disadvantageous.
 212 class WebContentsCaptureMachine
 213     : public VideoCaptureMachine,
 214       public WebContentsObserver {
 215  public:
 216   WebContentsCaptureMachine(int render_process_id, int render_view_id);
 217   virtual ~WebContentsCaptureMachine();
 218
 219   // VideoCaptureMachine overrides.
 220   virtual bool Start(
 221       const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy) OVERRIDE;
 222   virtual void Stop(const base::Closure& callback) OVERRIDE;
 223
 224   // Starts a copy from the backing store or the composited surface. Must be run
 225   // on the UI BrowserThread. |deliver_frame_cb| will be run when the operation
 226   // completes. The copy will occur to |target|.
 227   //
 228   // This may be used as a ContentCaptureSubscription::CaptureCallback.
 229   void Capture(const base::TimeTicks& start_time,
 230                const scoped_refptr<media::VideoFrame>& target,
 231                const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 232                    deliver_frame_cb);
 233
 234   // content::WebContentsObserver implementation.
 235   virtual void DidShowFullscreenWidget(int routing_id) OVERRIDE {
 236     fullscreen_widget_id_ = routing_id;
 237     RenewFrameSubscription();
 238   }
 239
 240   virtual void DidDestroyFullscreenWidget(int routing_id) OVERRIDE {
 241     DCHECK_EQ(fullscreen_widget_id_, routing_id);
 242     fullscreen_widget_id_ = MSG_ROUTING_NONE;
 243     RenewFrameSubscription();
 244   }
 245
 246   virtual void RenderViewReady() OVERRIDE {
 247     RenewFrameSubscription();
 248   }
 249
 250   virtual void AboutToNavigateRenderView(RenderViewHost* rvh) OVERRIDE {
 251     RenewFrameSubscription();
 252   }
 253
 254   virtual void DidNavigateMainFrame(
 255       const LoadCommittedDetails& details,
 256       const FrameNavigateParams& params) OVERRIDE {
 257     RenewFrameSubscription();
 258   }
 259
 260   virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
 261
 262  private:
 263   // Starts observing the web contents, returning false if lookup fails.
 264   bool StartObservingWebContents();
 265
 266   // Helper function to determine the view that we are currently tracking.
 267   RenderWidgetHost* GetTarget();
 268
 269   // Response callback for RenderWidgetHost::CopyFromBackingStore().
 270   void DidCopyFromBackingStore(
 271       const base::TimeTicks& start_time,
 272       const scoped_refptr<media::VideoFrame>& target,
 273       const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 274           deliver_frame_cb,
 275       bool success,
 276       const SkBitmap& bitmap);
 277
 278   // Response callback for RWHVP::CopyFromCompositingSurfaceToVideoFrame().
 279   void DidCopyFromCompositingSurfaceToVideoFrame(
 280       const base::TimeTicks& start_time,
 281       const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 282           deliver_frame_cb,
 283       bool success);
 284
 285   // Remove the old subscription, and start a new one. This should be called
 286   // after any change to the WebContents that affects the RenderWidgetHost or
 287   // attached views.
 288   void RenewFrameSubscription();
 289
 290   // Parameters saved in constructor.
 291   const int initial_render_process_id_;
 292   const int initial_render_view_id_;
 293
 294   // A dedicated worker thread on which SkBitmap->VideoFrame conversion will
 295   // occur. Only used when this activity cannot be done on the GPU.
 296   scoped_ptr<base::Thread> render_thread_;
 297
 298   // Makes all the decisions about which frames to copy, and how.
 299   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
 300
 301   // Routing ID of any active fullscreen render widget or MSG_ROUTING_NONE
 302   // otherwise.
 303   int fullscreen_widget_id_;
 304
 305   // Last known RenderView size.
 306   gfx::Size last_view_size_;
 307
 308   // Responsible for forwarding events from the active RenderWidgetHost to the
 309   // oracle, and initiating captures accordingly.
 310   scoped_ptr<ContentCaptureSubscription> subscription_;
 311
 312   // Weak pointer factory used to invalidate callbacks.
 313   base::WeakPtrFactory<WebContentsCaptureMachine> weak_ptr_factory_;
 314
 315   DISALLOW_COPY_AND_ASSIGN(WebContentsCaptureMachine);
 316 };
 317
 318 // Responsible for logging the effective frame rate.
 319 // TODO(nick): Make this compatible with the push model and hook it back up.
 320 class VideoFrameDeliveryLog {
 321  public:
 322   VideoFrameDeliveryLog();
 323
 324   // Treat |frame_number| as having been delivered, and update the
 325   // frame rate statistics accordingly.
 326   void ChronicleFrameDelivery(int frame_number);
 327
 328  private:
 329   // The following keep track of and log the effective frame rate whenever
 330   // verbose logging is turned on.
 331   base::TimeTicks last_frame_rate_log_time_;
 332   int count_frames_rendered_;
 333   int last_frame_number_;
 334
 335   DISALLOW_COPY_AND_ASSIGN(VideoFrameDeliveryLog);
 336 };
 337
 338 bool FrameSubscriber::ShouldCaptureFrame(
 339     base::TimeTicks present_time,
 340     scoped_refptr<media::VideoFrame>* storage,
 341     DeliverFrameCallback* deliver_frame_cb) {
 342   TRACE_EVENT1("mirroring", "FrameSubscriber::ShouldCaptureFrame",
 343                "instance", this);
 344
 345   ThreadSafeCaptureOracle::CaptureFrameCallback capture_frame_cb;
 346   bool oracle_decision = oracle_proxy_->ObserveEventAndDecideCapture(
 347       event_type_, present_time, storage, &capture_frame_cb);
 348
 349   *deliver_frame_cb = base::Bind(&InvokeCaptureFrameCallback, capture_frame_cb);
 350   return oracle_decision;
 351 }
 352
 353 ContentCaptureSubscription::ContentCaptureSubscription(
 354     const RenderWidgetHost& source,
 355     const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 356     const CaptureCallback& capture_callback)
 357     : render_process_id_(source.GetProcess()->GetID()),
 358       render_view_id_(source.GetRoutingID()),
 359       paint_subscriber_(VideoCaptureOracle::kSoftwarePaint, oracle_proxy),
 360       timer_subscriber_(VideoCaptureOracle::kTimerPoll, oracle_proxy),
 361       capture_callback_(capture_callback),
 362       timer_(true, true) {
 363   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 364
 365   RenderWidgetHostViewPort* view =
 366       RenderWidgetHostViewPort::FromRWHV(source.GetView());
 367
 368   // Subscribe to accelerated presents. These will be serviced directly by the
 369   // oracle.
 370   if (view && kAcceleratedSubscriberIsSupported) {
 371     scoped_ptr<RenderWidgetHostViewFrameSubscriber> subscriber(
 372         new FrameSubscriber(VideoCaptureOracle::kCompositorUpdate,
 373             oracle_proxy));
 374     view->BeginFrameSubscription(subscriber.Pass());
 375   }
 376
 377   // Subscribe to software paint events. This instance will service these by
 378   // reflecting them back to the WebContentsCaptureMachine via
 379   // |capture_callback|.
 380   registrar_.Add(
 381       this, content::NOTIFICATION_RENDER_WIDGET_HOST_DID_UPDATE_BACKING_STORE,
 382       Source<RenderWidgetHost>(&source));
 383
 384   // Subscribe to timer events. This instance will service these as well.
 385   timer_.Start(FROM_HERE, oracle_proxy->capture_period(),
 386                base::Bind(&ContentCaptureSubscription::OnTimer,
 387                           base::Unretained(this)));
 388 }
 389
 390 ContentCaptureSubscription::~ContentCaptureSubscription() {
 391   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 392   if (kAcceleratedSubscriberIsSupported) {
 393     RenderViewHost* source = RenderViewHost::FromID(render_process_id_,
 394                                                     render_view_id_);
 395     if (source) {
 396       RenderWidgetHostViewPort* view =
 397           RenderWidgetHostViewPort::FromRWHV(source->GetView());
 398       if (view)
 399         view->EndFrameSubscription();
 400     }
 401   }
 402 }
 403
 404 void ContentCaptureSubscription::Observe(
 405     int type,
 406     const content::NotificationSource& source,
 407     const content::NotificationDetails& details) {
 408   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 409   DCHECK_EQ(NOTIFICATION_RENDER_WIDGET_HOST_DID_UPDATE_BACKING_STORE, type);
 410
 411   RenderWidgetHostImpl* rwh =
 412       RenderWidgetHostImpl::From(Source<RenderWidgetHost>(source).ptr());
 413
 414   // This message occurs on window resizes and visibility changes even when
 415   // accelerated compositing is active, so we need to filter out these cases.
 416   if (!rwh || !rwh->GetView() || (rwh->is_accelerated_compositing_active() &&
 417                                   rwh->GetView()->IsSurfaceAvailableForCopy()))
 418     return;
 419
 420   TRACE_EVENT1("mirroring", "ContentCaptureSubscription::Observe",
 421                "instance", this);
 422
 423   base::Closure copy_done_callback;
 424   scoped_refptr<media::VideoFrame> frame;
 425   RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback deliver_frame_cb;
 426   const base::TimeTicks start_time = base::TimeTicks::Now();
 427   if (paint_subscriber_.ShouldCaptureFrame(start_time,
 428                                            &frame,
 429                                            &deliver_frame_cb)) {
 430     // This message happens just before paint. If we post a task to do the copy,
 431     // it should run soon after the paint.
 432     BrowserThread::PostTask(
 433         BrowserThread::UI, FROM_HERE,
 434         base::Bind(capture_callback_, start_time, frame, deliver_frame_cb));
 435   }
 436 }
 437
 438 void ContentCaptureSubscription::OnTimer() {
 439   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 440   TRACE_EVENT0("mirroring", "ContentCaptureSubscription::OnTimer");
 441
 442   scoped_refptr<media::VideoFrame> frame;
 443   RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback deliver_frame_cb;
 444
 445   const base::TimeTicks start_time = base::TimeTicks::Now();
 446   if (timer_subscriber_.ShouldCaptureFrame(start_time,
 447                                            &frame,
 448                                            &deliver_frame_cb)) {
 449     capture_callback_.Run(start_time, frame, deliver_frame_cb);
 450   }
 451 }
 452
 453 void RenderVideoFrame(const SkBitmap& input,
 454                       const scoped_refptr<media::VideoFrame>& output,
 455                       const base::Callback<void(bool)>& done_cb) {
 456   base::ScopedClosureRunner failure_handler(base::Bind(done_cb, false));
 457
 458   SkAutoLockPixels locker(input);
 459
 460   // Sanity-check the captured bitmap.
 461   if (input.empty() ||
 462       !input.readyToDraw() ||
 463       input.config() != SkBitmap::kARGB_8888_Config ||
 464       input.width() < 2 || input.height() < 2) {
 465     DVLOG(1) << "input unacceptable (size="
 466              << input.getSize()
 467              << ", ready=" << input.readyToDraw()
 468              << ", config=" << input.config() << ')';
 469     return;
 470   }
 471
 472   // Sanity-check the output buffer.
 473   if (output->format() != media::VideoFrame::I420) {
 474     NOTREACHED();
 475     return;
 476   }
 477
 478   // Calculate the width and height of the content region in the |output|, based
 479   // on the aspect ratio of |input|.
 480   gfx::Rect region_in_frame = ComputeYV12LetterboxRegion(
 481       output->coded_size(), gfx::Size(input.width(), input.height()));
 482
 483   // Scale the bitmap to the required size, if necessary.
 484   SkBitmap scaled_bitmap;
 485   if (input.width() != region_in_frame.width() ||
 486       input.height() != region_in_frame.height()) {
 487
 488     skia::ImageOperations::ResizeMethod method;
 489     if (input.width() < region_in_frame.width() ||
 490         input.height() < region_in_frame.height()) {
 491       // Avoid box filtering when magnifying, because it's actually
 492       // nearest-neighbor.
 493       method = skia::ImageOperations::RESIZE_HAMMING1;
 494     } else {
 495       method = skia::ImageOperations::RESIZE_BOX;
 496     }
 497
 498     TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", output.get(), "Scale");
 499     scaled_bitmap = skia::ImageOperations::Resize(input, method,
 500                                                   region_in_frame.width(),
 501                                                   region_in_frame.height());
 502   } else {
 503     scaled_bitmap = input;
 504   }
 505
 506   TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", output.get(), "YUV");
 507   {
 508     SkAutoLockPixels scaled_bitmap_locker(scaled_bitmap);
 509
 510     media::CopyRGBToVideoFrame(
 511         reinterpret_cast<uint8*>(scaled_bitmap.getPixels()),
 512         scaled_bitmap.rowBytes(),
 513         region_in_frame,
 514         output.get());
 515   }
 516
 517   // The result is now ready.
 518   ignore_result(failure_handler.Release());
 519   done_cb.Run(true);
 520 }
 521
 522 VideoFrameDeliveryLog::VideoFrameDeliveryLog()
 523     : last_frame_rate_log_time_(),
 524       count_frames_rendered_(0),
 525       last_frame_number_(0) {
 526 }
 527
 528 void VideoFrameDeliveryLog::ChronicleFrameDelivery(int frame_number) {
 529   // Log frame rate, if verbose logging is turned on.
 530   static const base::TimeDelta kFrameRateLogInterval =
 531       base::TimeDelta::FromSeconds(10);
 532   const base::TimeTicks now = base::TimeTicks::Now();
 533   if (last_frame_rate_log_time_.is_null()) {
 534     last_frame_rate_log_time_ = now;
 535     count_frames_rendered_ = 0;
 536     last_frame_number_ = frame_number;
 537   } else {
 538     ++count_frames_rendered_;
 539     const base::TimeDelta elapsed = now - last_frame_rate_log_time_;
 540     if (elapsed >= kFrameRateLogInterval) {
 541       const double measured_fps =
 542           count_frames_rendered_ / elapsed.InSecondsF();
 543       const int frames_elapsed = frame_number - last_frame_number_;
 544       const int count_frames_dropped = frames_elapsed - count_frames_rendered_;
 545       DCHECK_LE(0, count_frames_dropped);
 546       UMA_HISTOGRAM_PERCENTAGE(
 547           "TabCapture.FrameDropPercentage",
 548           (count_frames_dropped * 100 + frames_elapsed / 2) / frames_elapsed);
 549       UMA_HISTOGRAM_COUNTS(
 550           "TabCapture.FrameRate",
 551           static_cast<int>(measured_fps));
 552       VLOG(1) << "Current measured frame rate for "
 553               << "WebContentsVideoCaptureDevice is " << measured_fps << " FPS.";
 554       last_frame_rate_log_time_ = now;
 555       count_frames_rendered_ = 0;
 556       last_frame_number_ = frame_number;
 557     }
 558   }
 559 }
 560
 561 WebContentsCaptureMachine::WebContentsCaptureMachine(int render_process_id,
 562                                                      int render_view_id)
 563     : initial_render_process_id_(render_process_id),
 564       initial_render_view_id_(render_view_id),
 565       fullscreen_widget_id_(MSG_ROUTING_NONE),
 566       weak_ptr_factory_(this) {}
 567
 568 WebContentsCaptureMachine::~WebContentsCaptureMachine() {
 569   BrowserThread::PostBlockingPoolTask(
 570       FROM_HERE,
 571       base::Bind(&DeleteOnWorkerThread, base::Passed(&render_thread_),
 572                  base::Bind(&base::DoNothing)));
 573 }
 574
 575 bool WebContentsCaptureMachine::Start(
 576     const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy) {
 577   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 578   DCHECK(!started_);
 579
 580   DCHECK(oracle_proxy.get());
 581   oracle_proxy_ = oracle_proxy;
 582
 583   render_thread_.reset(new base::Thread("WebContentsVideo_RenderThread"));
 584   if (!render_thread_->Start()) {
 585     DVLOG(1) << "Failed to spawn render thread.";
 586     render_thread_.reset();
 587     return false;
 588   }
 589
 590   if (!StartObservingWebContents()) {
 591     DVLOG(1) << "Failed to observe web contents.";
 592     render_thread_.reset();
 593     return false;
 594   }
 595
 596   started_ = true;
 597   return true;
 598 }
 599
 600 void WebContentsCaptureMachine::Stop(const base::Closure& callback) {
 601   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 602   subscription_.reset();
 603   if (web_contents()) {
 604     web_contents()->DecrementCapturerCount();
 605     Observe(NULL);
 606   }
 607
 608   // Any callback that intend to use render_thread_ will not work after it is
 609   // passed.
 610   weak_ptr_factory_.InvalidateWeakPtrs();
 611
 612   // The render thread cannot be stopped on the UI thread, so post a message
 613   // to the thread pool used for blocking operations.
 614   BrowserThread::PostBlockingPoolTask(
 615       FROM_HERE,
 616       base::Bind(&DeleteOnWorkerThread, base::Passed(&render_thread_),
 617                  callback));
 618
 619   started_ = false;
 620 }
 621
 622 void WebContentsCaptureMachine::Capture(
 623     const base::TimeTicks& start_time,
 624     const scoped_refptr<media::VideoFrame>& target,
 625     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 626         deliver_frame_cb) {
 627   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 628
 629   RenderWidgetHost* rwh = GetTarget();
 630   RenderWidgetHostViewPort* view =
 631       rwh ? RenderWidgetHostViewPort::FromRWHV(rwh->GetView()) : NULL;
 632   if (!view || !rwh) {
 633     deliver_frame_cb.Run(base::TimeTicks(), false);
 634     return;
 635   }
 636
 637   gfx::Size video_size = target->coded_size();
 638   gfx::Size view_size = view->GetViewBounds().size();
 639   gfx::Size fitted_size;
 640   if (!view_size.IsEmpty()) {
 641     fitted_size = ComputeYV12LetterboxRegion(video_size, view_size).size();
 642   }
 643   if (view_size != last_view_size_) {
 644     last_view_size_ = view_size;
 645
 646     // Measure the number of kilopixels.
 647     UMA_HISTOGRAM_COUNTS_10000(
 648         "TabCapture.ViewChangeKiloPixels",
 649         view_size.width() * view_size.height() / 1024);
 650   }
 651
 652   if (!view->IsSurfaceAvailableForCopy()) {
 653     // Fallback to the more expensive renderer-side copy if the surface and
 654     // backing store are not accessible.
 655     rwh->GetSnapshotFromRenderer(
 656         gfx::Rect(),
 657         base::Bind(&WebContentsCaptureMachine::DidCopyFromBackingStore,
 658                    weak_ptr_factory_.GetWeakPtr(),
 659                    start_time, target, deliver_frame_cb));
 660   } else if (view->CanCopyToVideoFrame()) {
 661     view->CopyFromCompositingSurfaceToVideoFrame(
 662         gfx::Rect(view_size),
 663         target,
 664         base::Bind(&WebContentsCaptureMachine::
 665                         DidCopyFromCompositingSurfaceToVideoFrame,
 666                    weak_ptr_factory_.GetWeakPtr(),
 667                    start_time, deliver_frame_cb));
 668   } else {
 669     rwh->CopyFromBackingStore(
 670         gfx::Rect(),
 671         fitted_size,  // Size here is a request not always honored.
 672         base::Bind(&WebContentsCaptureMachine::DidCopyFromBackingStore,
 673                    weak_ptr_factory_.GetWeakPtr(),
 674                    start_time, target, deliver_frame_cb));
 675   }
 676 }
 677
 678 bool WebContentsCaptureMachine::StartObservingWebContents() {
 679   // Look-up the RenderViewHost and, from that, the WebContents that wraps it.
 680   // If successful, begin observing the WebContents instance.
 681   //
 682   // Why this can be unsuccessful: The request for mirroring originates in a
 683   // render process, and this request is based on the current RenderView
 684   // associated with a tab.  However, by the time we get up-and-running here,
 685   // there have been multiple back-and-forth IPCs between processes, as well as
 686   // a bit of indirection across threads.  It's easily possible that, in the
 687   // meantime, the original RenderView may have gone away.
 688   RenderViewHost* const rvh =
 689       RenderViewHost::FromID(initial_render_process_id_,
 690                              initial_render_view_id_);
 691   DVLOG_IF(1, !rvh) << "RenderViewHost::FromID("
 692                     << initial_render_process_id_ << ", "
 693                     << initial_render_view_id_ << ") returned NULL.";
 694   Observe(rvh ? WebContents::FromRenderViewHost(rvh) : NULL);
 695
 696   WebContentsImpl* contents = static_cast<WebContentsImpl*>(web_contents());
 697   if (contents) {
 698     contents->IncrementCapturerCount(oracle_proxy_->GetCaptureSize());
 699     fullscreen_widget_id_ = contents->GetFullscreenWidgetRoutingID();
 700     RenewFrameSubscription();
 701     return true;
 702   }
 703
 704   DVLOG(1) << "WebContents::FromRenderViewHost(" << rvh << ") returned NULL.";
 705   return false;
 706 }
 707
 708 void WebContentsCaptureMachine::WebContentsDestroyed(
 709     WebContents* web_contents) {
 710   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 711
 712   subscription_.reset();
 713   web_contents->DecrementCapturerCount();
 714   oracle_proxy_->ReportError("WebContentsDestroyed()");
 715 }
 716
 717 RenderWidgetHost* WebContentsCaptureMachine::GetTarget() {
 718   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 719   if (!web_contents())
 720     return NULL;
 721
 722   RenderWidgetHost* rwh = NULL;
 723   if (fullscreen_widget_id_ != MSG_ROUTING_NONE) {
 724     RenderProcessHost* process = web_contents()->GetRenderProcessHost();
 725     if (process)
 726       rwh = RenderWidgetHost::FromID(process->GetID(), fullscreen_widget_id_);
 727   } else {
 728     rwh = web_contents()->GetRenderViewHost();
 729   }
 730
 731   return rwh;
 732 }
 733
 734 void WebContentsCaptureMachine::DidCopyFromBackingStore(
 735     const base::TimeTicks& start_time,
 736     const scoped_refptr<media::VideoFrame>& target,
 737     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 738         deliver_frame_cb,
 739     bool success,
 740     const SkBitmap& bitmap) {
 741   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 742
 743   base::TimeTicks now = base::TimeTicks::Now();
 744   DCHECK(render_thread_.get());
 745   if (success) {
 746     UMA_HISTOGRAM_TIMES("TabCapture.CopyTimeBitmap", now - start_time);
 747     TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", target.get(),
 748                                  "Render");
 749     render_thread_->message_loop_proxy()->PostTask(FROM_HERE, base::Bind(
 750         &RenderVideoFrame, bitmap, target,
 751         base::Bind(deliver_frame_cb, start_time)));
 752   } else {
 753     // Capture can fail due to transient issues, so just skip this frame.
 754     DVLOG(1) << "CopyFromBackingStore failed; skipping frame.";
 755     deliver_frame_cb.Run(start_time, false);
 756   }
 757 }
 758
 759 void WebContentsCaptureMachine::DidCopyFromCompositingSurfaceToVideoFrame(
 760     const base::TimeTicks& start_time,
 761     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 762         deliver_frame_cb,
 763     bool success) {
 764   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 765   base::TimeTicks now = base::TimeTicks::Now();
 766
 767   if (success) {
 768     UMA_HISTOGRAM_TIMES("TabCapture.CopyTimeVideoFrame", now - start_time);
 769   } else {
 770     // Capture can fail due to transient issues, so just skip this frame.
 771     DVLOG(1) << "CopyFromCompositingSurface failed; skipping frame.";
 772   }
 773   deliver_frame_cb.Run(start_time, success);
 774 }
 775
 776 void WebContentsCaptureMachine::RenewFrameSubscription() {
 777   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 778
 779   // Always destroy the old subscription before creating a new one.
 780   subscription_.reset();
 781
 782   RenderWidgetHost* rwh = GetTarget();
 783   if (!rwh || !rwh->GetView())
 784     return;
 785
 786   subscription_.reset(new ContentCaptureSubscription(*rwh, oracle_proxy_,
 787       base::Bind(&WebContentsCaptureMachine::Capture,
 788                  weak_ptr_factory_.GetWeakPtr())));
 789 }
 790
 791 }  // namespace
 792
 793 WebContentsVideoCaptureDevice::WebContentsVideoCaptureDevice(
 794     int render_process_id, int render_view_id)
 795     : core_(new ContentVideoCaptureDeviceCore(scoped_ptr<VideoCaptureMachine>(
 796         new WebContentsCaptureMachine(render_process_id, render_view_id)))) {}
 797
 798 WebContentsVideoCaptureDevice::~WebContentsVideoCaptureDevice() {
 799   DVLOG(2) << "WebContentsVideoCaptureDevice@" << this << " destroying.";
 800 }
 801
 802 // static
 803 media::VideoCaptureDevice* WebContentsVideoCaptureDevice::Create(
 804     const std::string& device_id) {
 805   // Parse device_id into render_process_id and render_view_id.
 806   int render_process_id = -1;
 807   int render_view_id = -1;
 808   if (!WebContentsCaptureUtil::ExtractTabCaptureTarget(
 809            device_id, &render_process_id, &render_view_id)) {
 810     return NULL;
 811   }
 812
 813   return new WebContentsVideoCaptureDevice(render_process_id, render_view_id);
 814 }
 815
 816 void WebContentsVideoCaptureDevice::AllocateAndStart(
 817     const media::VideoCaptureParams& params,
 818     scoped_ptr<Client> client) {
 819   DVLOG(1) << "Allocating " << params.requested_format.frame_size.ToString();
 820   core_->AllocateAndStart(params, client.Pass());
 821 }
 822
 823 void WebContentsVideoCaptureDevice::StopAndDeAllocate() {
 824   core_->StopAndDeAllocate();
 825 }
 826
 827 }  // namespace content