New method CreateScaledFrame in the VideoFrameFactory interface.

webrtc/media/base/videoframefactory.h

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MEDIA_BASE_VIDEOFRAMEFACTORY_H_
 #define WEBRTC_MEDIA_BASE_VIDEOFRAMEFACTORY_H_
 
 #include <memory>
 
 #include "webrtc/media/base/videoframe.h"
 
 namespace cricket {
 
 struct CapturedFrame;
 class VideoFrame;
 
 // Creates cricket::VideoFrames, or a subclass of cricket::VideoFrame
 // depending on the subclass of VideoFrameFactory.
 class VideoFrameFactory {
  public:
   VideoFrameFactory() : apply_rotation_(false) {}
   virtual ~VideoFrameFactory() {}
 
+  // Convert a CapturedFrame to a VideoFrame. |width| and |height|
+  // give the desired size, and the factory is expected to first crop
+  // the frame to get a matching aspect ratio, and then scale it to
+  // the right size. The size refers the the image before application
+  // of |input_frame->rotation|. Subclasses usually only need to
+  // override CreateScaledCroppedFrame, see below.
+  virtual std::unique_ptr<VideoFrame> CreateScaledFrame(
+      const CapturedFrame* input_frame,
+      int width,
+      int height) const;
+
+  // The CreateAliasedFrame methods are deprecated, since cropping is
+  // no longer supported, and we don't want raw pointer return types.
+  // TODO(nisse): Delete when all users are updated.
+
   // The returned frame aliases the aliased_frame if the input color
   // space allows for aliasing, otherwise a color conversion will
   // occur. Returns NULL if conversion fails.
 
   // The returned frame will be a center crop of |input_frame| with
   // size |cropped_width| x |cropped_height|.
   virtual VideoFrame* CreateAliasedFrame(const CapturedFrame* input_frame,
                                          int cropped_width,
-                                         int cropped_height) const = 0;
-
+                                         int cropped_height) const {
+    // Dummy default implementation, to make it easier to delete in
+    // subclasses.
+    return NULL;

[perkj_webrtc, 2016/05/11 10:05:17]

return nullptr;

+  }
   // The returned frame will be a center crop of |input_frame| with size
   // |cropped_width| x |cropped_height|, scaled to |output_width| x
   // |output_height|.
   virtual VideoFrame* CreateAliasedFrame(const CapturedFrame* input_frame,
                                          int cropped_input_width,
                                          int cropped_input_height,
                                          int output_width,
                                          int output_height) const;
 
   void SetApplyRotation(bool enable) { apply_rotation_ = enable; }
 
  protected:
+  // Similar to CreateScaledFrame, but gets cropping parameters as
+  // inputs, and relies on the caller to choose them so that aspect
+  // ration is preserved.
+  virtual std::unique_ptr<VideoFrame> CreateScaledCroppedFrame(
+      const CapturedFrame* input_frame,
+      int crop_x,
+      int crop_y,
+      int crop_width,

[perkj_webrtc, 2016/05/11 10:05:17]

please document what the arguments mean.

[nisse-webrtc, 2016/05/12 12:23:06]

I'm adding a comment. I'm also renaming the method, for consistency with
I420Buffer::CropAndScale.

+      int crop_height,
+      int dst_width,
+      int dst_height) const;
+
   bool apply_rotation_;
 
  private:
   // An internal frame buffer to avoid reallocations. It is mutable because it
   // does not affect behaviour, only performance.
   mutable std::unique_ptr<VideoFrame> output_frame_;
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_MEDIA_BASE_VIDEOFRAMEFACTORY_H_