Cast: Basic cast_receiver API for chrome.

media/video/capture/video_capturer_source.h

+// Copyright (c) 2015 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 MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURER_SOURCE_H_
+#define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURER_SOURCE_H_
+
+#include <string>
+#include <vector>
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "media/base/media_export.h"
+#include "media/base/video_frame.h"
+#include "media/video/capture/video_capture_types.h"
+
+namespace media {
+
+// VideoCapturerSource is an interface representing the source for
+// captured video.  An implementation will periodically call the frame
+// callback with new video frames.
+class MEDIA_EXPORT VideoCapturerSource

[Alpha Left Google, 2015/02/04 03:07:52]

I think this is best put in media/base. media/video/capture is mostly for
implemention with hardware.

[hubbe, 2015/02/05 20:23:00]

That leaves a rather awkward dependency on video_capture_types.h in media/base

+    : public base::RefCountedThreadSafe<media::VideoCapturerSource> {

[Alpha Left Google, 2015/02/04 03:07:53]

There's no need for this to be ref counted thread safe. 

[hubbe, 2015/02/05 20:23:00]

Done.

+ public:
+  // This callback is used to deliver video frames.
+  //
+  // |estimated_capture_time| - The capture time of the delivered video
+  // frame. This field represents the local time at which either: 1) the frame
+  // was generated, if it was done so locally; or 2) the targeted play-out time
+  // of the frame, if it was generated from a remote source. Either way, an
+  // implementation should not present the frame before this point-in-time. This
+  // value is NOT a high-resolution timestamp, and so it should not be used as a
+  // presentation time; but, instead, it should be used for buffering playback
+  // and for A/V synchronization purposes. NOTE: It is possible for this value
+  // to be null if the current implementation lacks this timing information.
+  //
+  // |video_frame->timestamp()| gives the presentation timestamp of the video
+  // frame relative to the first frame generated by the corresponding source.
+  // Because a source can start generating frames before a subscriber is added,
+  // the first video frame delivered may not have timestamp equal to 0.
+  typedef base::Callback<

[Alpha Left Google, 2015/02/04 03:07:52]

Please remove the definition of VideoCaptureDeliverFrameCB from
media_stream_video_sink.h. There should just be one definition.

[hubbe, 2015/02/05 20:23:00]

Done.

+   void(const scoped_refptr<media::VideoFrame>& video_frame,
+        const media::VideoCaptureFormat& format,
+        const base::TimeTicks& estimated_capture_time)>
+      VideoCaptureDeliverFrameCB;
+
+  typedef base::Callback<void(const media::VideoCaptureFormats&)>
+      VideoCaptureDeviceFormatsCB;
+
+  typedef base::Callback<void(bool)> RunningCallback;
+
+  // Collects the formats that can currently be used.
+  // |max_requested_height|, |max_requested_width|, and
+  // |max_requested_frame_rate| is used by Tab and Screen capture to decide what
+  // resolution/framerate to generate. |callback| is triggered when the formats
+  // have been collected.
+  virtual void GetCurrentSupportedFormats(
+      int max_requested_width,
+      int max_requested_height,
+      double max_requested_frame_rate,
+      const VideoCaptureDeviceFormatsCB& callback) = 0;
+
+  // Starts capturing frames using the resolution in |params|.
+  // |new_frame_callback| is triggered when a new video frame is available.
+  // If capturing is started successfully then |running_callback| will be
+  // called with a parameter of true. /* FIXME */
+  // If capturing fails to start or stopped due to an external event then
+  // |running_callback| will be called with a parameter of false.
+  virtual void StartCapture(

[Alpha Left Google, 2015/02/04 03:07:52]

I see this interface is extracted from MediaStreamVideoCapturerSource. The
details of threading must be considered carefully.
MediaStreamVideoCapturerSource was designed to operate on the render thread
while VideoCaptureDeliverFrameCB was to be called on IO thread only. The details
of threading is available for code in content but not in media/. I think this
method should take a message loop for calling |new_frame_callback|.

[hubbe, 2015/02/05 20:23:00]

Added task runner, added documentation.

+      const media::VideoCaptureParams& params,
+      const VideoCaptureDeliverFrameCB& new_frame_callback,
+      const RunningCallback& running_callback) = 0;
+
+  // Stops capturing frames and clears all callbacks including the
+  // SupportedFormatsCallback callback. Waits until it is safe to

[Alpha Left Google, 2015/02/04 03:07:52]

There shouldn't be any wait.

[hubbe, 2015/02/05 20:23:00]

Changed to not require wait.

+  // delete this object.
+  virtual void StopCapture() = 0;

[Alpha Left Google, 2015/02/04 03:07:52]

Note that it is okay that |new_frame_callback| is called after StopCapture() is
called. There is no need to wait. This method is asynchronous (unlike
AudioCapturerSource) and this information should be in the comments.

[hubbe, 2015/02/05 20:23:00]

Changed to state that there might be additional calls after stop.

+
+ protected:
+  friend class base::RefCountedThreadSafe<VideoCapturerSource>;
+  virtual ~VideoCapturerSource();
+};
+
+}  // namespace media
+
+#endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURER_SOURCE_H_