[Cast] VideoFrameFactory interface to vend frames with encoder affinity.

media/cast/cast_sender.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.
 //
 // This is the main interface for the cast sender.
 //
 // The AudioFrameInput, VideoFrameInput and PacketReciever interfaces should
 // be accessed from the main thread.
 
 #ifndef MEDIA_CAST_CAST_SENDER_H_
@@ skipping 18 matching lines @@
 class VideoSender;
 
 class VideoFrameInput : public base::RefCountedThreadSafe<VideoFrameInput> {
  public:
   // Insert video frames into Cast sender. Frames will be encoded, packetized
   // and sent to the network.
   virtual void InsertRawVideoFrame(
       const scoped_refptr<media::VideoFrame>& video_frame,
       const base::TimeTicks& capture_time) = 0;
 
+  // Creates a |VideoFrame| suitable for input via |InsertRawVideoFrame|. Frames
+  // obtained in this manner may provide benefits such memory reuse and affinity
+  // with the encoder. The format is guaranteed to be I420 or NV12.
+  virtual scoped_refptr<VideoFrame> CreateFrame(base::TimeDelta timestamp) = 0;

[Alpha Left Google, 2014/11/17 20:23:14]

What if CastSender is not yet initialized? Then there won't be an encoder and
this method wouldn't know what kind of frames to create. Code change is not
needed, I think you just need to clarify in comments.

[jfroy, 2014/11/17 21:23:05]

OK, I'll clarify that if the initialization status is not video initialized,
you'll get back null. I thought I didn't need to clarify because if video
initialization fails, CastSender does not create a VideoFrameInput object and
thus you won't ever be able to call that method.

[Alpha Left Google, 2014/11/18 02:57:58]

You're right. VideoFrameInput is not available until video sending is
initialized.

+
  protected:
   virtual ~VideoFrameInput() {}
 
  private:
   friend class base::RefCountedThreadSafe<VideoFrameInput>;
 };
 
 class AudioFrameInput : public base::RefCountedThreadSafe<AudioFrameInput> {
  public:
   // Insert audio frames into Cast sender. Frames will be encoded, packetized
@@ skipping 41 matching lines @@
   // Change the target delay. This is only valid if the receiver
   // supports the "adaptive_target_delay" rtp extension.
   virtual void SetTargetPlayoutDelay(
       base::TimeDelta new_target_playout_delay) = 0;
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_CAST_SENDER_H_