[Cast] Software encoder support for varying video frame sizes.

media/cast/sender/video_encoder.h

 // Copyright 2014 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_CAST_SENDER_VIDEO_ENCODER_H_
 #define MEDIA_CAST_SENDER_VIDEO_ENCODER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "media/base/video_frame.h"
 #include "media/cast/cast_config.h"
 #include "media/cast/cast_environment.h"
 
 namespace media {
 namespace cast {
 
 class VideoFrameFactory;
 
 // All these functions are called from the main cast thread.
 class VideoEncoder {
  public:
   typedef base::Callback<void(scoped_ptr<EncodedFrame>)> FrameEncodedCallback;
 
   virtual ~VideoEncoder() {}
 
+  // Returns true if the size of video frames passed in successive calls to
+  // EncodedVideoFrame() can vary.
+  virtual bool CanEncodeVariedFrameSizes() const;

[hubbe, 2015/01/31 00:55:51]

I think it would be better to make this pure virtual to make sure that people
who extend VideoEncoder don't forget to override this function.

[miu, 2015/01/31 04:53:04]

Done.

+
   // If true is returned, the Encoder has accepted the request and will process
   // it asynchronously, running |frame_encoded_callback| on the MAIN
   // CastEnvironment thread with the result.  If false is returned, nothing
   // happens and the callback will not be run.
   virtual bool EncodeVideoFrame(
       const scoped_refptr<media::VideoFrame>& video_frame,
       const base::TimeTicks& reference_time,
       const FrameEncodedCallback& frame_encoded_callback) = 0;
 
   // Inform the encoder about the new target bit rate.
   virtual void SetBitRate(int new_bit_rate) = 0;
 
   // Inform the encoder to encode the next frame as a key frame.
   virtual void GenerateKeyFrame() = 0;
 
   // Inform the encoder to only reference frames older or equal to frame_id;
   virtual void LatestFrameIdToReference(uint32 frame_id) = 0;
 
   // Creates a |VideoFrameFactory| object to vend |VideoFrame| object with
   // encoder affinity (defined as offering some sort of performance benefit).
   // This is an optional capability and by default returns null.
   virtual scoped_ptr<VideoFrameFactory> CreateVideoFrameFactory();
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_SENDER_VIDEO_ENCODER_H_