2 files changed, 58 insertions, 23 deletions

diff --git a/remoting/host/video_scheduler.cc b/remoting/host/video_scheduler.cc
index 7fc1983..a346d04 100644
--- a/remoting/host/video_scheduler.cc
+++ b/remoting/host/video_scheduler.cc
@@ -30,6 +30,10 @@ namespace remoting {
 // TODO(hclam): Move this value to CaptureScheduler.
 static const int kMaxPendingFrames = 2;
 
+// Interval between empty keep-alive frames. These frames are sent only
+// when there are no real video frames being sent.
+static const int kKeepAlivePacketIntervalMs = 500;
+
 VideoScheduler::VideoScheduler(
     scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> encode_task_runner,
@@ -68,16 +72,22 @@ void VideoScheduler::OnCaptureCompleted(webrtc::DesktopFrame* frame) {
 
   capture_pending_ = false;
 
+  if (!frame) {
+    LOG(ERROR) << "Capture failed.";
+    return;
+  }
+
   scoped_ptr<webrtc::DesktopFrame> owned_frame(frame);
 
-  if (frame) {
-    scheduler_.RecordCaptureTime(
-        base::TimeDelta::FromMilliseconds(frame->capture_time_ms()));
-  }
+  scheduler_.RecordCaptureTime(
+      base::TimeDelta::FromMilliseconds(frame->capture_time_ms()));
 
-  encode_task_runner_->PostTask(
-      FROM_HERE, base::Bind(&VideoScheduler::EncodeFrame, this,
-                            base::Passed(&owned_frame), sequence_number_));
+  // Encode and send only non-empty frames.
+  if (!frame->updated_region().is_empty()) {
+    encode_task_runner_->PostTask(
+        FROM_HERE, base::Bind(&VideoScheduler::EncodeFrame, this,
+                              base::Passed(&owned_frame), sequence_number_));
+  }
 
   // If a frame was skipped, try to capture it again.
   if (did_skip_frame_) {
@@ -123,8 +133,10 @@ void VideoScheduler::Stop() {
   cursor_stub_ = NULL;
   video_stub_ = NULL;
 
-  capture_task_runner_->PostTask(FROM_HERE,
-      base::Bind(&VideoScheduler::StopOnCaptureThread, this));
+  keep_alive_timer_.reset();
+
+  capture_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&VideoScheduler::StopOnCaptureThread, this));
 }
 
 void VideoScheduler::Pause(bool pause) {
@@ -172,6 +184,9 @@ void VideoScheduler::StartOnCaptureThread() {
   capturer_->Start(this);
 
   capture_timer_.reset(new base::OneShotTimer<VideoScheduler>());
+  keep_alive_timer_.reset(new base::DelayTimer<VideoScheduler>(
+      FROM_HERE, base::TimeDelta::FromMilliseconds(kKeepAlivePacketIntervalMs),
+      this, &VideoScheduler::SendKeepAlivePacket));
 
   // Capture first frame immedately.
   CaptureNextFrame();
@@ -249,19 +264,39 @@ void VideoScheduler::SendVideoPacket(scoped_ptr<VideoPacket> packet) {
     return;
 
   video_stub_->ProcessVideoPacket(
-      packet.Pass(), base::Bind(&VideoScheduler::VideoFrameSentCallback, this));
+      packet.Pass(), base::Bind(&VideoScheduler::OnVideoPacketSent, this));
 }
 
-void VideoScheduler::VideoFrameSentCallback() {
+void VideoScheduler::OnVideoPacketSent() {
   DCHECK(network_task_runner_->BelongsToCurrentThread());
 
   if (!video_stub_)
     return;
 
+  keep_alive_timer_->Reset();
+
   capture_task_runner_->PostTask(
       FROM_HERE, base::Bind(&VideoScheduler::FrameCaptureCompleted, this));
 }
 
+void VideoScheduler::SendKeepAlivePacket() {
+  DCHECK(network_task_runner_->BelongsToCurrentThread());
+
+  if (!video_stub_)
+    return;
+
+  video_stub_->ProcessVideoPacket(
+      scoped_ptr<VideoPacket>(new VideoPacket()),
+      base::Bind(&VideoScheduler::OnKeepAlivePacketSent, this));
+}
+
+void VideoScheduler::OnKeepAlivePacketSent() {
+  DCHECK(network_task_runner_->BelongsToCurrentThread());
+
+  if (keep_alive_timer_)
+    keep_alive_timer_->Reset();
+}
+
 void VideoScheduler::SendCursorShape(
     scoped_ptr<protocol::CursorShapeInfo> cursor_shape) {
   DCHECK(network_task_runner_->BelongsToCurrentThread());
@@ -278,17 +313,7 @@ void VideoScheduler::EncodeFrame(
     scoped_ptr<webrtc::DesktopFrame> frame,
     int64 sequence_number) {
   DCHECK(encode_task_runner_->BelongsToCurrentThread());
-
-  // If there is nothing to encode then send an empty keep-alive packet.
-  if (!frame || frame->updated_region().is_empty()) {
-    scoped_ptr<VideoPacket> packet(new VideoPacket());
-    packet->set_client_sequence_number(sequence_number);
-    network_task_runner_->PostTask(
-        FROM_HERE, base::Bind(&VideoScheduler::SendVideoPacket, this,
-                              base::Passed(&packet)));
-    capture_task_runner_->DeleteSoon(FROM_HERE, frame.release());
-    return;
-  }
+  DCHECK(!frame->updated_region().is_empty());
 
   scoped_ptr<VideoPacket> packet = encoder_->Encode(*frame);
   packet->set_client_sequence_number(sequence_number);
diff --git a/remoting/host/video_scheduler.h b/remoting/host/video_scheduler.h
index f2eabd9..94fc795 100644
--- a/remoting/host/video_scheduler.h
+++ b/remoting/host/video_scheduler.h
@@ -140,7 +140,13 @@ class VideoScheduler : public base::RefCountedThreadSafe<VideoScheduler>,
 
   // Callback passed to |video_stub_| for the last packet in each frame, to
   // rate-limit frame captures to network throughput.
-  void VideoFrameSentCallback();
+  void OnVideoPacketSent();
+
+  // Called by |keep_alive_timer_|.
+  void SendKeepAlivePacket();
+
+  // Callback for |video_stub_| called after a keep-alive packet is sent.
+  void OnKeepAlivePacketSent();
 
   // Send updated cursor shape to client.
   void SendCursorShape(scoped_ptr<protocol::CursorShapeInfo> cursor_shape);
@@ -173,6 +179,10 @@ class VideoScheduler : public base::RefCountedThreadSafe<VideoScheduler>,
   // Timer used to schedule CaptureNextFrame().
   scoped_ptr<base::OneShotTimer<VideoScheduler> > capture_timer_;
 
+  // Timer used to ensure that we send empty keep-alive frames to the client
+  // even when the video stream is paused or encoder is busy.
+  scoped_ptr<base::DelayTimer<VideoScheduler> > keep_alive_timer_;
+
   // The number of frames being processed, i.e. frames that we are currently
   // capturing, encoding or sending. The value is capped at 2 to minimize
   // latency.