Define the interface for MediaStreamVideoSource.

content/public/renderer/media_stream_video_source.h

+// Copyright 2013 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.
+
+#ifndef CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_VIDEO_SOURCE_H_
+#define CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_VIDEO_SOURCE_H_

[perkj_chrome, 2013/12/18 08:15:10]

Why does the source have to be in content public? Put in renderer/media?

[Ronghua Wu (Left Chromium), 2013/12/18 21:22:23]

I don't really know what is the content public about. Just thought to put this
aside to video sink. Where do you think I should put this?
content/renderer/media?

+
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
+#include "content/common/content_export.h"
+#include "content/public/renderer/media_stream_sink.h"
+#include "third_party/WebKit/public/platform/WebMediaConstraints.h"
+
+namespace media {
+class VideoFrame;
+}
+
+namespace blink {
+class WebMediaStreamTrack;
+}
+
+namespace content {
+
+class MediaStreamVideoSink;
+
+// MediaStreamVideoSink is an interface used for sending video frames to a

[perkj_chrome, 2013/12/18 08:15:10]

update the comment.

[Ronghua Wu (Left Chromium), 2013/12/18 21:22:23]

Done.

+// Media Stream Video Track.
+// http://dev.w3.org/2011/webrtc/editor/getusermedia.html
+// All methods calls will be done from the main render thread.
+class CONTENT_EXPORT MediaStreamVideoSource : public MediaStreamSink {

[perkj_chrome, 2013/12/18 08:15:10]

Should this inherit from MediaStreamSourceExtraData - same as
MediaStreamVideoTrack?
It should be owned by blink source extra data and by inheriting from
MediaStreamSourceExtraData an implementation get access to the blink source
object.

Do you need to inherit from MediaStreamSink? I know that it says so in the
design doc but I am not sure how we want to do this. Either we have multiple
implementations of a MediaStreamVideoSource. 1. local capture, 1 Nacl, 1 remote
tracks . Or we have one implementation of MediaStreamSource and each
specialization is implemented by a delegate instead and the MediaStreamSource
inherit from MediaStreamVideoSink or similar and owns the delegate.

[Jói, 2013/12/18 13:47:07]

I agree we might want to hold off on inheriting from MediaStreamSink until we're
sure that's the appropriate interface for media providers that push data to the
source to use.

[Ronghua Wu (Left Chromium), 2013/12/18 21:22:23]

Ok. Inheriting from MediaStreamSourceExtraData instread. Use PutVideoFrame to
distinguish from MediaStreamVideoSink interface.

+ public:
+  bool Register(MediaStreamVideoSink* track,

[perkj_chrome, 2013/12/18 08:15:10]

One thing that came up yesterday was applyConstraints. Our idea was to handle
that by Register/ Unregister with constraints to the source. But the source
might have to do something async, ex restart the camera and only when that has
happened would we know if Register succeeded. 
So the source might have to tell the track using a callback if Register with the
new constraint succeeded or not.
I don't think such a callback belong in MediaStreamVideoSink since things like a
renderer don't need this. 
Would it therefore make sence to have Register take a pointer to a
MediaStreamVideoTrack object instead? MediaStreamVideoTrack can maybe inherit
from MediaStreamVideoSink + add new methods. 

btw- webrtc_audio_capturer (which is the audio source) call this AddTrack and
RemoveTrack instead of Register and UnRegister. Maybe we should do the same.

[perkj_chrome, 2013/12/18 08:15:10]

Comment on thread requirements please. Here and the other methods. 
For the time being, all methods will be called on the main render thread. See
comment in MediaStreamVideoSink.

[Jói, 2013/12/18 13:47:07]

If MediaStreamVideoTrack has some methods that a source would need to use and
that aren't appropriate for a sink interface, then I would tend to agree, this
should register tracks rather than sinks.

[Ronghua Wu (Left Chromium), 2013/12/18 21:22:23]

It's at the beginning of the class.

[Ronghua Wu (Left Chromium), 2013/12/18 21:22:23]

Ok. I thought we are not suppose to reopen the camera in any case. That's why I
thought this can return synchronizly and don't need a callback, in which case
MediaStreamVideoSink will be the only interface needed from the track.

Change to MediaStreamVideoTrack SGTM regardless.

+                const blink::WebMediaConstraints& constrains);
+  bool Unregister(MediaStreamVideoSink* track);
+
+ protected:
+  // An implementation of MediaStreamVideoSource should call OnVideoFrame when
+  // it is ready to send a frame to video tracks.
+  virtual void OnVideoFrame(const scoped_refptr<media::VideoFrame>& frame);
+  virtual ~MediaStreamVideoSource();
+};
+
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_VIDEO_SOURCE_H_