content/browser/media/capture/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 RenderWidget'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/media/capture/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/media/capture/content_video_capture_device_core.h"
  66 #include "content/browser/media/capture/video_capture_oracle.h"
  67 #include "content/browser/media/capture/web_contents_capture_util.h"
  68 #include "content/browser/media/capture/web_contents_tracker.h"
  69 #include "content/browser/renderer_host/render_widget_host_impl.h"
  70 #include "content/browser/renderer_host/render_widget_host_view_base.h"
  71 #include "content/public/browser/browser_thread.h"
  72 #include "content/public/browser/notification_observer.h"
  73 #include "content/public/browser/notification_registrar.h"
  74 #include "content/public/browser/notification_source.h"
  75 #include "content/public/browser/notification_types.h"
  76 #include "content/public/browser/render_process_host.h"
  77 #include "content/public/browser/render_widget_host_view.h"
  78 #include "content/public/browser/render_widget_host_view_frame_subscriber.h"
  79 #include "content/public/browser/web_contents.h"
  80 #include "media/base/video_capture_types.h"
  81 #include "media/base/video_util.h"
  82 #include "skia/ext/image_operations.h"
  83 #include "third_party/skia/include/core/SkBitmap.h"
  84 #include "third_party/skia/include/core/SkColor.h"
  85 #include "ui/gfx/display.h"
  86 #include "ui/gfx/geometry/size.h"
  87 #include "ui/gfx/geometry/size_conversions.h"
  88 #include "ui/gfx/screen.h"
  89
  90 namespace content {
  91
  92 namespace {
  93
  94 // Compute a letterbox region, aligned to even coordinates.
  95 gfx::Rect ComputeYV12LetterboxRegion(const gfx::Rect& visible_rect,
  96                                      const gfx::Size& content_size) {
  97
  98   gfx::Rect result = media::ComputeLetterboxRegion(visible_rect, content_size);
  99
 100   result.set_x(MakeEven(result.x()));
 101   result.set_y(MakeEven(result.y()));
 102   result.set_width(std::max(kMinFrameWidth, MakeEven(result.width())));
 103   result.set_height(std::max(kMinFrameHeight, MakeEven(result.height())));
 104
 105   return result;
 106 }
 107
 108 void DeleteOnWorkerThread(scoped_ptr<base::Thread> render_thread,
 109                           const base::Closure& callback) {
 110   render_thread.reset();
 111
 112   // After thread join call the callback on UI thread.
 113   BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, callback);
 114 }
 115
 116 // Responsible for logging the effective frame rate.
 117 class VideoFrameDeliveryLog {
 118  public:
 119   VideoFrameDeliveryLog();
 120
 121   // Report that the frame posted with |frame_time| has been delivered.
 122   void ChronicleFrameDelivery(base::TimeTicks frame_time);
 123
 124  private:
 125   // The following keep track of and log the effective frame rate whenever
 126   // verbose logging is turned on.
 127   base::TimeTicks last_frame_rate_log_time_;
 128   int count_frames_rendered_;
 129
 130   DISALLOW_COPY_AND_ASSIGN(VideoFrameDeliveryLog);
 131 };
 132
 133 // FrameSubscriber is a proxy to the ThreadSafeCaptureOracle that's compatible
 134 // with RenderWidgetHostViewFrameSubscriber. We create one per event type.
 135 class FrameSubscriber : public RenderWidgetHostViewFrameSubscriber {
 136  public:
 137   FrameSubscriber(VideoCaptureOracle::Event event_type,
 138                   const scoped_refptr<ThreadSafeCaptureOracle>& oracle,
 139                   VideoFrameDeliveryLog* delivery_log)
 140       : event_type_(event_type),
 141         oracle_proxy_(oracle),
 142         delivery_log_(delivery_log) {}
 143
 144   bool ShouldCaptureFrame(
 145       const gfx::Rect& damage_rect,
 146       base::TimeTicks present_time,
 147       scoped_refptr<media::VideoFrame>* storage,
 148       RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback*
 149           deliver_frame_cb) override;
 150
 151  private:
 152   const VideoCaptureOracle::Event event_type_;
 153   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
 154   VideoFrameDeliveryLog* const delivery_log_;
 155 };
 156
 157 // ContentCaptureSubscription is the relationship between a RenderWidgetHost
 158 // whose content is updating, a subscriber that is deciding which of these
 159 // updates to capture (and where to deliver them to), and a callback that
 160 // knows how to do the capture and prepare the result for delivery.
 161 //
 162 // In practice, this means (a) installing a RenderWidgetHostFrameSubscriber in
 163 // the RenderWidgetHostView, to process updates that occur via accelerated
 164 // compositing, (b) installing itself as an observer of updates to the
 165 // RenderWidgetHost's backing store, to hook updates that occur via software
 166 // rendering, and (c) running a timer to possibly initiate non-event-driven
 167 // captures that the subscriber might request.
 168 //
 169 // All of this happens on the UI thread, although the
 170 // RenderWidgetHostViewFrameSubscriber we install may be dispatching updates
 171 // autonomously on some other thread.
 172 class ContentCaptureSubscription : public content::NotificationObserver {
 173  public:
 174   typedef base::Callback<
 175       void(const base::TimeTicks&,
 176            const scoped_refptr<media::VideoFrame>&,
 177            const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&)>
 178       CaptureCallback;
 179
 180   // Create a subscription. Whenever a manual capture is required, the
 181   // subscription will invoke |capture_callback| on the UI thread to do the
 182   // work.
 183   ContentCaptureSubscription(
 184       const RenderWidgetHost& source,
 185       const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 186       const CaptureCallback& capture_callback);
 187   ~ContentCaptureSubscription() override;
 188
 189   // content::NotificationObserver implementation.
 190   void Observe(int type,
 191                const content::NotificationSource& source,
 192                const content::NotificationDetails& details) override;
 193
 194  private:
 195   void OnTimer();
 196
 197   // Maintain a weak reference to the RenderWidgetHost (via its routing ID),
 198   // since the instance could be destroyed externally during the lifetime of
 199   // |this|.
 200   const int render_process_id_;
 201   const int render_widget_id_;
 202
 203   VideoFrameDeliveryLog delivery_log_;
 204   FrameSubscriber paint_subscriber_;
 205   FrameSubscriber timer_subscriber_;
 206   content::NotificationRegistrar registrar_;
 207   CaptureCallback capture_callback_;
 208   base::Timer timer_;
 209
 210   DISALLOW_COPY_AND_ASSIGN(ContentCaptureSubscription);
 211 };
 212
 213 // Render the SkBitmap |input| into the given VideoFrame buffer |output|, then
 214 // invoke |done_cb| to indicate success or failure. |input| is expected to be
 215 // ARGB. |output| must be YV12 or I420. Colorspace conversion is always done.
 216 // Scaling and letterboxing will be done as needed.
 217 //
 218 // This software implementation should be used only when GPU acceleration of
 219 // these activities is not possible. This operation may be expensive (tens to
 220 // hundreds of milliseconds), so the caller should ensure that it runs on a
 221 // thread where such a pause would cause UI jank.
 222 void RenderVideoFrame(const SkBitmap& input,
 223                       const scoped_refptr<media::VideoFrame>& output,
 224                       const base::Callback<void(bool)>& done_cb);
 225
 226 // Renews capture subscriptions based on feedback from WebContentsTracker, and
 227 // also executes copying of the backing store on the UI BrowserThread.
 228 class WebContentsCaptureMachine : public VideoCaptureMachine {
 229  public:
 230   WebContentsCaptureMachine(int render_process_id, int main_render_frame_id);
 231   ~WebContentsCaptureMachine() override;
 232
 233   // VideoCaptureMachine overrides.
 234   bool Start(const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 235              const media::VideoCaptureParams& params) override;
 236   void Stop(const base::Closure& callback) override;
 237
 238   // Starts a copy from the backing store or the composited surface. Must be run
 239   // on the UI BrowserThread. |deliver_frame_cb| will be run when the operation
 240   // completes. The copy will occur to |target|.
 241   //
 242   // This may be used as a ContentCaptureSubscription::CaptureCallback.
 243   void Capture(const base::TimeTicks& start_time,
 244                const scoped_refptr<media::VideoFrame>& target,
 245                const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 246                    deliver_frame_cb);
 247
 248  private:
 249   bool IsStarted() const;
 250
 251   // Computes the preferred size of the target RenderWidget for optimal capture.
 252   gfx::Size ComputeOptimalTargetSize() const;
 253
 254   // Response callback for RenderWidgetHost::CopyFromBackingStore().
 255   void DidCopyFromBackingStore(
 256       const base::TimeTicks& start_time,
 257       const scoped_refptr<media::VideoFrame>& target,
 258       const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 259           deliver_frame_cb,
 260       const SkBitmap& bitmap,
 261       ReadbackResponse response);
 262
 263   // Response callback for RWHVP::CopyFromCompositingSurfaceToVideoFrame().
 264   void DidCopyFromCompositingSurfaceToVideoFrame(
 265       const base::TimeTicks& start_time,
 266       const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 267           deliver_frame_cb,
 268       bool success);
 269
 270   // Remove the old subscription, and start a new one if |rwh| is not NULL.
 271   void RenewFrameSubscription(RenderWidgetHost* rwh);
 272
 273   // Parameters saved in constructor.
 274   const int initial_render_process_id_;
 275   const int initial_main_render_frame_id_;
 276
 277   // Tracks events and calls back to RenewFrameSubscription() to maintain
 278   // capture on the correct RenderWidgetHost.
 279   const scoped_refptr<WebContentsTracker> tracker_;
 280
 281   // A dedicated worker thread on which SkBitmap->VideoFrame conversion will
 282   // occur. Only used when this activity cannot be done on the GPU.
 283   scoped_ptr<base::Thread> render_thread_;
 284
 285   // Makes all the decisions about which frames to copy, and how.
 286   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
 287
 288   // Video capture parameters that this machine is started with.
 289   media::VideoCaptureParams capture_params_;
 290
 291   // Last known RenderView size.
 292   gfx::Size last_view_size_;
 293
 294   // Responsible for forwarding events from the active RenderWidgetHost to the
 295   // oracle, and initiating captures accordingly.
 296   scoped_ptr<ContentCaptureSubscription> subscription_;
 297
 298   // Weak pointer factory used to invalidate callbacks.
 299   // NOTE: Weak pointers must be invalidated before all other member variables.
 300   base::WeakPtrFactory<WebContentsCaptureMachine> weak_ptr_factory_;
 301
 302   DISALLOW_COPY_AND_ASSIGN(WebContentsCaptureMachine);
 303 };
 304
 305 bool FrameSubscriber::ShouldCaptureFrame(
 306     const gfx::Rect& damage_rect,
 307     base::TimeTicks present_time,
 308     scoped_refptr<media::VideoFrame>* storage,
 309     DeliverFrameCallback* deliver_frame_cb) {
 310   TRACE_EVENT1("mirroring", "FrameSubscriber::ShouldCaptureFrame",
 311                "instance", this);
 312
 313   ThreadSafeCaptureOracle::CaptureFrameCallback capture_frame_cb;
 314   bool oracle_decision = oracle_proxy_->ObserveEventAndDecideCapture(
 315       event_type_, damage_rect, present_time, storage, &capture_frame_cb);
 316
 317   if (!capture_frame_cb.is_null())
 318     *deliver_frame_cb = base::Bind(capture_frame_cb, *storage);
 319   if (oracle_decision)
 320     delivery_log_->ChronicleFrameDelivery(present_time);
 321   return oracle_decision;
 322 }
 323
 324 ContentCaptureSubscription::ContentCaptureSubscription(
 325     const RenderWidgetHost& source,
 326     const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 327     const CaptureCallback& capture_callback)
 328     : render_process_id_(source.GetProcess()->GetID()),
 329       render_widget_id_(source.GetRoutingID()),
 330       delivery_log_(),
 331       paint_subscriber_(VideoCaptureOracle::kSoftwarePaint, oracle_proxy,
 332                         &delivery_log_),
 333       timer_subscriber_(VideoCaptureOracle::kTimerPoll, oracle_proxy,
 334                         &delivery_log_),
 335       capture_callback_(capture_callback),
 336       timer_(true, true) {
 337   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 338
 339   RenderWidgetHostView* const view = source.GetView();
 340
 341   // Subscribe to accelerated presents. These will be serviced directly by the
 342   // oracle.
 343   if (view) {
 344     scoped_ptr<RenderWidgetHostViewFrameSubscriber> subscriber(
 345         new FrameSubscriber(VideoCaptureOracle::kCompositorUpdate,
 346             oracle_proxy, &delivery_log_));
 347     view->BeginFrameSubscription(subscriber.Pass());
 348   }
 349
 350   // Subscribe to software paint events. This instance will service these by
 351   // reflecting them back to the WebContentsCaptureMachine via
 352   // |capture_callback|.
 353   registrar_.Add(
 354       this, content::NOTIFICATION_RENDER_WIDGET_HOST_DID_UPDATE_BACKING_STORE,
 355       Source<RenderWidgetHost>(&source));
 356
 357   // Subscribe to timer events. This instance will service these as well.
 358   timer_.Start(FROM_HERE, oracle_proxy->min_capture_period(),
 359                base::Bind(&ContentCaptureSubscription::OnTimer,
 360                           base::Unretained(this)));
 361 }
 362
 363 ContentCaptureSubscription::~ContentCaptureSubscription() {
 364   // If the BrowserThreads have been torn down, then the browser is in the final
 365   // stages of exiting and it is dangerous to take any further action.  We must
 366   // return early.  http://crbug.com/396413
 367   if (!BrowserThread::IsMessageLoopValid(BrowserThread::UI))
 368     return;
 369
 370   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 371   RenderWidgetHost* const source =
 372       RenderWidgetHost::FromID(render_process_id_, render_widget_id_);
 373   RenderWidgetHostView* const view = source ? source->GetView() : NULL;
 374   if (view)
 375     view->EndFrameSubscription();
 376 }
 377
 378 void ContentCaptureSubscription::Observe(
 379     int type,
 380     const content::NotificationSource& source,
 381     const content::NotificationDetails& details) {
 382   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 383   DCHECK_EQ(NOTIFICATION_RENDER_WIDGET_HOST_DID_UPDATE_BACKING_STORE, type);
 384
 385   RenderWidgetHostImpl* rwh =
 386       RenderWidgetHostImpl::From(Source<RenderWidgetHost>(source).ptr());
 387
 388   // This message occurs on window resizes and visibility changes even when
 389   // accelerated compositing is active, so we need to filter out these cases.
 390   if (!rwh || !rwh->GetView())
 391     return;
 392   // Mac sends DID_UPDATE_BACKING_STORE messages to inform the capture system
 393   // of new software compositor frames, so always treat these messages as
 394   // signals of a new frame on Mac.
 395   // http://crbug.com/333986
 396 #if !defined(OS_MACOSX)
 397   if (rwh->GetView()->IsSurfaceAvailableForCopy())
 398     return;
 399 #endif
 400
 401   TRACE_EVENT1("mirroring", "ContentCaptureSubscription::Observe",
 402                "instance", this);
 403
 404   base::Closure copy_done_callback;
 405   scoped_refptr<media::VideoFrame> frame;
 406   RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback deliver_frame_cb;
 407   const base::TimeTicks start_time = base::TimeTicks::Now();
 408   if (paint_subscriber_.ShouldCaptureFrame(gfx::Rect(),
 409                                            start_time,
 410                                            &frame,
 411                                            &deliver_frame_cb)) {
 412     // This message happens just before paint. If we post a task to do the copy,
 413     // it should run soon after the paint.
 414     BrowserThread::PostTask(
 415         BrowserThread::UI, FROM_HERE,
 416         base::Bind(capture_callback_, start_time, frame, deliver_frame_cb));
 417   }
 418 }
 419
 420 void ContentCaptureSubscription::OnTimer() {
 421   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 422   TRACE_EVENT0("mirroring", "ContentCaptureSubscription::OnTimer");
 423
 424   scoped_refptr<media::VideoFrame> frame;
 425   RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback deliver_frame_cb;
 426
 427   const base::TimeTicks start_time = base::TimeTicks::Now();
 428   if (timer_subscriber_.ShouldCaptureFrame(gfx::Rect(),
 429                                            start_time,
 430                                            &frame,
 431                                            &deliver_frame_cb)) {
 432     capture_callback_.Run(start_time, frame, deliver_frame_cb);
 433   }
 434 }
 435
 436 void RenderVideoFrame(const SkBitmap& input,
 437                       const scoped_refptr<media::VideoFrame>& output,
 438                       const base::Callback<void(bool)>& done_cb) {
 439   base::ScopedClosureRunner failure_handler(base::Bind(done_cb, false));
 440
 441   SkAutoLockPixels locker(input);
 442
 443   // Sanity-check the captured bitmap.
 444   if (input.empty() ||
 445       !input.readyToDraw() ||
 446       input.colorType() != kN32_SkColorType ||
 447       input.width() < 2 || input.height() < 2) {
 448     DVLOG(1) << "input unacceptable (size="
 449              << input.getSize()
 450              << ", ready=" << input.readyToDraw()
 451              << ", colorType=" << input.colorType() << ')';
 452     return;
 453   }
 454
 455   // Sanity-check the output buffer.
 456   if (output->format() != media::VideoFrame::I420) {
 457     NOTREACHED();
 458     return;
 459   }
 460
 461   // Calculate the width and height of the content region in the |output|, based
 462   // on the aspect ratio of |input|.
 463   gfx::Rect region_in_frame = ComputeYV12LetterboxRegion(
 464       output->visible_rect(), gfx::Size(input.width(), input.height()));
 465
 466   // Scale the bitmap to the required size, if necessary.
 467   SkBitmap scaled_bitmap;
 468   if (input.width() != region_in_frame.width() ||
 469       input.height() != region_in_frame.height()) {
 470
 471     skia::ImageOperations::ResizeMethod method;
 472     if (input.width() < region_in_frame.width() ||
 473         input.height() < region_in_frame.height()) {
 474       // Avoid box filtering when magnifying, because it's actually
 475       // nearest-neighbor.
 476       method = skia::ImageOperations::RESIZE_HAMMING1;
 477     } else {
 478       method = skia::ImageOperations::RESIZE_BOX;
 479     }
 480
 481     TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", output.get(), "Scale");
 482     scaled_bitmap = skia::ImageOperations::Resize(input, method,
 483                                                   region_in_frame.width(),
 484                                                   region_in_frame.height());
 485   } else {
 486     scaled_bitmap = input;
 487   }
 488
 489   TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", output.get(), "YUV");
 490   {
 491     SkAutoLockPixels scaled_bitmap_locker(scaled_bitmap);
 492
 493     media::CopyRGBToVideoFrame(
 494         reinterpret_cast<uint8*>(scaled_bitmap.getPixels()),
 495         scaled_bitmap.rowBytes(),
 496         region_in_frame,
 497         output.get());
 498   }
 499
 500   // The result is now ready.
 501   ignore_result(failure_handler.Release());
 502   done_cb.Run(true);
 503 }
 504
 505 VideoFrameDeliveryLog::VideoFrameDeliveryLog()
 506     : last_frame_rate_log_time_(),
 507       count_frames_rendered_(0) {
 508 }
 509
 510 void VideoFrameDeliveryLog::ChronicleFrameDelivery(base::TimeTicks frame_time) {
 511   // Log frame rate, if verbose logging is turned on.
 512   static const base::TimeDelta kFrameRateLogInterval =
 513       base::TimeDelta::FromSeconds(10);
 514   if (last_frame_rate_log_time_.is_null()) {
 515     last_frame_rate_log_time_ = frame_time;
 516     count_frames_rendered_ = 0;
 517   } else {
 518     ++count_frames_rendered_;
 519     const base::TimeDelta elapsed = frame_time - last_frame_rate_log_time_;
 520     if (elapsed >= kFrameRateLogInterval) {
 521       const double measured_fps =
 522           count_frames_rendered_ / elapsed.InSecondsF();
 523       UMA_HISTOGRAM_COUNTS(
 524           "TabCapture.FrameRate",
 525           static_cast<int>(measured_fps));
 526       VLOG(1) << "Current measured frame rate for "
 527               << "WebContentsVideoCaptureDevice is " << measured_fps << " FPS.";
 528       last_frame_rate_log_time_ = frame_time;
 529       count_frames_rendered_ = 0;
 530     }
 531   }
 532 }
 533
 534 WebContentsCaptureMachine::WebContentsCaptureMachine(int render_process_id,
 535                                                      int main_render_frame_id)
 536     : initial_render_process_id_(render_process_id),
 537       initial_main_render_frame_id_(main_render_frame_id),
 538       tracker_(new WebContentsTracker(true)),
 539       weak_ptr_factory_(this) {}
 540
 541 WebContentsCaptureMachine::~WebContentsCaptureMachine() {}
 542
 543 bool WebContentsCaptureMachine::IsStarted() const {
 544   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 545   return weak_ptr_factory_.HasWeakPtrs();
 546 }
 547
 548 bool WebContentsCaptureMachine::Start(
 549     const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
 550     const media::VideoCaptureParams& params) {
 551   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 552   DCHECK(!IsStarted());
 553
 554   DCHECK(oracle_proxy.get());
 555   oracle_proxy_ = oracle_proxy;
 556   capture_params_ = params;
 557
 558   render_thread_.reset(new base::Thread("WebContentsVideo_RenderThread"));
 559   if (!render_thread_->Start()) {
 560     DVLOG(1) << "Failed to spawn render thread.";
 561     render_thread_.reset();
 562     return false;
 563   }
 564
 565   // Note: Creation of the first WeakPtr in the following statement will cause
 566   // IsStarted() to return true from now on.
 567   tracker_->Start(initial_render_process_id_, initial_main_render_frame_id_,
 568                   base::Bind(&WebContentsCaptureMachine::RenewFrameSubscription,
 569                              weak_ptr_factory_.GetWeakPtr()));
 570
 571   return true;
 572 }
 573
 574 void WebContentsCaptureMachine::Stop(const base::Closure& callback) {
 575   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 576
 577   if (!IsStarted()) {
 578     callback.Run();
 579     return;
 580   }
 581
 582   // The following cancels any outstanding callbacks and causes IsStarted() to
 583   // return false from here onward.
 584   weak_ptr_factory_.InvalidateWeakPtrs();
 585
 586   // Note: RenewFrameSubscription() must be called before stopping |tracker_| so
 587   // the web_contents() can be notified that the capturing is ending.
 588   RenewFrameSubscription(NULL);
 589   tracker_->Stop();
 590
 591   // The render thread cannot be stopped on the UI thread, so post a message
 592   // to the thread pool used for blocking operations.
 593   if (render_thread_.get()) {
 594     BrowserThread::PostBlockingPoolTask(
 595         FROM_HERE,
 596         base::Bind(&DeleteOnWorkerThread, base::Passed(&render_thread_),
 597                    callback));
 598   }
 599 }
 600
 601 void WebContentsCaptureMachine::Capture(
 602     const base::TimeTicks& start_time,
 603     const scoped_refptr<media::VideoFrame>& target,
 604     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 605         deliver_frame_cb) {
 606   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 607
 608   RenderWidgetHost* rwh = tracker_->GetTargetRenderWidgetHost();
 609   RenderWidgetHostViewBase* view =
 610       rwh ? static_cast<RenderWidgetHostViewBase*>(rwh->GetView()) : NULL;
 611   if (!view) {
 612     deliver_frame_cb.Run(base::TimeTicks(), false);
 613     return;
 614   }
 615
 616   gfx::Size view_size = view->GetViewBounds().size();
 617   gfx::Size fitted_size;
 618   if (!view_size.IsEmpty()) {
 619     fitted_size = ComputeYV12LetterboxRegion(target->visible_rect(),
 620                                              view_size).size();
 621   }
 622   if (view_size != last_view_size_) {
 623     last_view_size_ = view_size;
 624
 625     // Measure the number of kilopixels.
 626     UMA_HISTOGRAM_COUNTS_10000(
 627         "TabCapture.ViewChangeKiloPixels",
 628         view_size.width() * view_size.height() / 1024);
 629   }
 630
 631   if (view->CanCopyToVideoFrame()) {
 632     view->CopyFromCompositingSurfaceToVideoFrame(
 633         gfx::Rect(view_size),
 634         target,
 635         base::Bind(&WebContentsCaptureMachine::
 636                         DidCopyFromCompositingSurfaceToVideoFrame,
 637                    weak_ptr_factory_.GetWeakPtr(),
 638                    start_time, deliver_frame_cb));
 639   } else {
 640     rwh->CopyFromBackingStore(
 641         gfx::Rect(),
 642         fitted_size,  // Size here is a request not always honored.
 643         base::Bind(&WebContentsCaptureMachine::DidCopyFromBackingStore,
 644                    weak_ptr_factory_.GetWeakPtr(),
 645                    start_time,
 646                    target,
 647                    deliver_frame_cb),
 648         kN32_SkColorType);
 649   }
 650 }
 651
 652 gfx::Size WebContentsCaptureMachine::ComputeOptimalTargetSize() const {
 653   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 654
 655   gfx::Size optimal_size = oracle_proxy_->GetCaptureSize();
 656
 657   // If the ratio between physical and logical pixels is greater than 1:1,
 658   // shrink |optimal_size| by that amount.  Then, when external code resizes the
 659   // render widget to the "preferred size," the widget will be physically
 660   // rendered at the exact capture size, thereby eliminating unnecessary scaling
 661   // operations in the graphics pipeline.
 662   RenderWidgetHost* const rwh = tracker_->GetTargetRenderWidgetHost();
 663   RenderWidgetHostView* const rwhv = rwh ? rwh->GetView() : NULL;
 664   if (rwhv) {
 665     const gfx::NativeView view = rwhv->GetNativeView();
 666     gfx::Screen* const screen = gfx::Screen::GetScreenFor(view);
 667     const gfx::Display display = screen->GetDisplayNearestWindow(view);
 668     const float scale = display.device_scale_factor();
 669     if (scale > 1.0f) {
 670       const gfx::Size shrunk_size(
 671           gfx::ToFlooredSize(gfx::ScaleSize(optimal_size, 1.0f / scale)));
 672       if (shrunk_size.width() > 0 && shrunk_size.height() > 0)
 673         optimal_size = shrunk_size;
 674     }
 675   }
 676
 677   VLOG(1) << "Computed optimal target size: " << optimal_size.ToString();
 678   return optimal_size;
 679 }
 680
 681 void WebContentsCaptureMachine::DidCopyFromBackingStore(
 682     const base::TimeTicks& start_time,
 683     const scoped_refptr<media::VideoFrame>& target,
 684     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 685         deliver_frame_cb,
 686     const SkBitmap& bitmap,
 687     ReadbackResponse response) {
 688   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 689
 690   base::TimeTicks now = base::TimeTicks::Now();
 691   DCHECK(render_thread_.get());
 692   if (response == READBACK_SUCCESS) {
 693     UMA_HISTOGRAM_TIMES("TabCapture.CopyTimeBitmap", now - start_time);
 694     TRACE_EVENT_ASYNC_STEP_INTO0("mirroring", "Capture", target.get(),
 695                                  "Render");
 696     render_thread_->message_loop_proxy()->PostTask(FROM_HERE, base::Bind(
 697         &RenderVideoFrame, bitmap, target,
 698         base::Bind(deliver_frame_cb, start_time)));
 699   } else {
 700     // Capture can fail due to transient issues, so just skip this frame.
 701     DVLOG(1) << "CopyFromBackingStore failed; skipping frame.";
 702     deliver_frame_cb.Run(start_time, false);
 703   }
 704 }
 705
 706 void WebContentsCaptureMachine::DidCopyFromCompositingSurfaceToVideoFrame(
 707     const base::TimeTicks& start_time,
 708     const RenderWidgetHostViewFrameSubscriber::DeliverFrameCallback&
 709         deliver_frame_cb,
 710     bool success) {
 711   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 712   base::TimeTicks now = base::TimeTicks::Now();
 713
 714   if (success) {
 715     UMA_HISTOGRAM_TIMES("TabCapture.CopyTimeVideoFrame", now - start_time);
 716   } else {
 717     // Capture can fail due to transient issues, so just skip this frame.
 718     DVLOG(1) << "CopyFromCompositingSurface failed; skipping frame.";
 719   }
 720   deliver_frame_cb.Run(start_time, success);
 721 }
 722
 723 void WebContentsCaptureMachine::RenewFrameSubscription(RenderWidgetHost* rwh) {
 724   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 725
 726   // Always destroy the old subscription before creating a new one.
 727   const bool had_subscription = !!subscription_;
 728   subscription_.reset();
 729
 730   DVLOG(1) << "Renewing frame subscription to RWH@" << rwh
 731            << ", had_subscription=" << had_subscription;
 732
 733   if (!rwh) {
 734     if (had_subscription && tracker_->web_contents())
 735       tracker_->web_contents()->DecrementCapturerCount();
 736     if (IsStarted()) {
 737       // Tracking of WebContents and/or its main frame has failed before Stop()
 738       // was called, so report this as an error:
 739       oracle_proxy_->ReportError("WebContents and/or main frame are gone.");
 740     }
 741     return;
 742   }
 743
 744   if (!had_subscription && tracker_->web_contents()) {
 745     tracker_->web_contents()->IncrementCapturerCount(
 746         ComputeOptimalTargetSize());
 747   }
 748
 749   subscription_.reset(new ContentCaptureSubscription(*rwh, oracle_proxy_,
 750       base::Bind(&WebContentsCaptureMachine::Capture,
 751                  weak_ptr_factory_.GetWeakPtr())));
 752 }
 753
 754 }  // namespace
 755
 756 WebContentsVideoCaptureDevice::WebContentsVideoCaptureDevice(
 757     int render_process_id, int main_render_frame_id)
 758     : core_(new ContentVideoCaptureDeviceCore(scoped_ptr<VideoCaptureMachine>(
 759         new WebContentsCaptureMachine(
 760             render_process_id, main_render_frame_id)))) {}
 761
 762 WebContentsVideoCaptureDevice::~WebContentsVideoCaptureDevice() {
 763   DVLOG(2) << "WebContentsVideoCaptureDevice@" << this << " destroying.";
 764 }
 765
 766 // static
 767 media::VideoCaptureDevice* WebContentsVideoCaptureDevice::Create(
 768     const std::string& device_id) {
 769   // Parse device_id into render_process_id and main_render_frame_id.
 770   int render_process_id = -1;
 771   int main_render_frame_id = -1;
 772   if (!WebContentsCaptureUtil::ExtractTabCaptureTarget(
 773            device_id, &render_process_id, &main_render_frame_id)) {
 774     return NULL;
 775   }
 776
 777   return new WebContentsVideoCaptureDevice(
 778       render_process_id, main_render_frame_id);
 779 }
 780
 781 void WebContentsVideoCaptureDevice::AllocateAndStart(
 782     const media::VideoCaptureParams& params,
 783     scoped_ptr<Client> client) {
 784   DVLOG(1) << "Allocating " << params.requested_format.frame_size.ToString();
 785   core_->AllocateAndStart(params, client.Pass());
 786 }
 787
 788 void WebContentsVideoCaptureDevice::StopAndDeAllocate() {
 789   core_->StopAndDeAllocate();
 790 }
 791
 792 }  // namespace content