Chrome MediaStream VideoTrack implementation.

content/renderer/media/rtc_video_renderer.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/rtc_video_renderer.h"
 
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "media/base/video_frame.h"
 #include "media/base/video_util.h"
 
 namespace content {
 
+// Reviewers ? Do you know a better way than to add this noop method?

[Jói, 2014/02/28 14:52:50]

You can use base::DoNothing (which is void DoNothing(void))

[perkj_chrome, 2014/03/02 09:20:44]

After discussion- this is needed to addref and release the original video frame.

+static void ReleaseOriginalFrame(const scoped_refptr<media::VideoFrame>& frame) {
+
+}
+
 RTCVideoRenderer::RTCVideoRenderer(
     const blink::WebMediaStreamTrack& video_track,
     const base::Closure& error_cb,
     const RepaintCB& repaint_cb)
     : error_cb_(error_cb),
       repaint_cb_(repaint_cb),
       message_loop_proxy_(base::MessageLoopProxy::current()),
       state_(STOPPED),
       first_frame_rendered_(false),
       video_track_(video_track) {
@@ skipping 57 matching lines @@
   DCHECK(message_loop_proxy_->BelongsToCurrentThread());
   if (state_ != STARTED) {
     return;
   }
 
   TRACE_EVENT_INSTANT1("rtc_video_renderer",
                        "OnVideoFrame",
                        TRACE_EVENT_SCOPE_THREAD,
                        "timestamp",
                        frame->GetTimestamp().InMilliseconds());
-  repaint_cb_.Run(frame);
   first_frame_rendered_ = true;
+
+  if (frame->format() == media::VideoFrame::I420) {
+     scoped_refptr<media::VideoFrame> yuv_frame =
+         media::VideoFrame::WrapExternalYuvData(
+             media::VideoFrame::YV12,
+             frame->coded_size(),
+             frame->visible_rect(),
+             frame->natural_size(),
+             frame->stride(media::VideoFrame::kYPlane),
+             frame->stride(media::VideoFrame::kUPlane),
+             frame->stride(media::VideoFrame::kVPlane),
+             frame->data(media::VideoFrame::kYPlane),
+             frame->data(media::VideoFrame::kUPlane),
+             frame->data(media::VideoFrame::kVPlane),
+             frame->GetTimestamp(),
+             // Can this be done without the function? Ie all I want is to add a refence and remove the reference once this callback is triggered.
+             base::Bind(&ReleaseOriginalFrame, frame));

[Alpha Left Google, 2014/02/28 02:49:22]

I'm not sure if this is correct.

Does this callback hold a reference to |frame|. I'll ask the author of Bind
tomorrow to clarify this.

[Jói, 2014/02/28 14:52:50]

You've bound both parameters so this wouldn't work with the do-nothing
ReleaseOriginalFrame function above. However, if you just use base::DoNothing
instead, this would work fine.

[Jói, 2014/02/28 15:46:10]

My mistake, I was assuming the WrapExternalYuvData function expected a callback
with a single parameter, but it actually wants a closure (i.e. no parameters).
So binding it the way you're doing is the right thing to do.

[perkj_chrome, 2014/03/02 09:20:44]

Done.

+     repaint_cb_.Run(yuv_frame);
+   } else {
+     repaint_cb_.Run(frame);

[Alpha Left Google, 2014/02/28 02:49:22]

nit: What about:

if (frame->format() != media::VideoFrame::I420) {
  repaint_cb.Run(framee);
  return;
}

// And then rest of the media::VideoFrame::WrapExternalYuvData code here.

[perkj_chrome, 2014/03/02 09:20:44]

Done.

+   }
 }
 
 void RTCVideoRenderer::MaybeRenderSignalingFrame() {
   // Render a small black frame if no frame has been rendered.
   // This is necessary to make sure audio can play if the video tag src is
   // a MediaStream video track that has been rejected, ended or disabled.
   if (first_frame_rendered_)
     return;
 
   const int kMinFrameSize = 2;
   const gfx::Size size(kMinFrameSize, kMinFrameSize);
   scoped_refptr<media::VideoFrame> video_frame =
       media::VideoFrame::CreateBlackFrame(size);
   OnVideoFrame(video_frame);
 }
 
 }  // namespace content