New method CreateScaledFrame in the VideoFrameFactory interface.

webrtc/media/base/videoframefactory.cc

 /*
  *  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.
  */
 
 #include "webrtc/media/base/videoframefactory.h"
 
 #include <algorithm>
 #include "webrtc/media/base/videocapturer.h"
 
 namespace cricket {
 
+std::unique_ptr<VideoFrame> VideoFrameFactory::CreateScaledFrame(
+    const CapturedFrame* input_frame,
+    int dst_width,
+    int dst_height) const {
+  // Size of the used portion of the input frame.
+  int crop_width = input_frame->width;
+  int crop_height = input_frame->height;
+
+  // Cropp the input frame, if needed to preserve aspect ratio.
+  long aspect_diff = static_cast<long>(crop_width) * dst_height -
+                     static_cast<long>(crop_height) * dst_width;
+  if (aspect_diff > 0) {
+    // Horizontal crop.
+
+    // TODO(nisse): Old code carried a comment saying that MJPG can

[perkj_webrtc, 2016/05/16 06:48:47]

You can add a DCHECK here if you want to check that input_frame is not MJPG. But
we don't support MJPG at this level anymore anyway, MGJP has already been
supported to I420 before reaching libjingle. 

+    // only be cropped vertically, and disabled horizontal cropping in
+    // that case. Still needed?
+    crop_width -= aspect_diff / dst_height;
+    RTC_DCHECK(crop_width > 0);
+  } else if (aspect_diff < 0) {
+    // Vertical crop.
+    crop_height -= (-aspect_diff) / dst_width;
+    RTC_DCHECK(crop_height > 0);
+  }
+  return CreateCroppedAndScaledFrame(
+      input_frame,
+      (input_frame->width - crop_width) / 2,
+      (input_frame->height - crop_height) / 2,
+      crop_width, crop_height,
+      dst_width, dst_height);
+}
+
+// For backwards compatibility, default implementation in terms of old
+// methods. Ignores the position of the cropping window, and leaves it
+// up to CreateAliasedFrame.
+// TODO(nisse): Delete when Chrome's subclass is updated.
+std::unique_ptr<VideoFrame> VideoFrameFactory::CreateCroppedAndScaledFrame(
+    const CapturedFrame* input_frame,
+    int crop_x,
+    int crop_y,
+    int crop_width,
+    int crop_height,
+    int dst_width,
+    int dst_height) const {
+  return std::unique_ptr<VideoFrame>(CreateAliasedFrame(
+      input_frame, crop_width, crop_height, dst_width, dst_height));
+}
+
 VideoFrame* VideoFrameFactory::CreateAliasedFrame(
     const CapturedFrame* input_frame,
     int cropped_input_width,
     int cropped_input_height,
     int output_width,
     int output_height) const {
   std::unique_ptr<VideoFrame> cropped_input_frame(CreateAliasedFrame(
       input_frame, cropped_input_width, cropped_input_height));
   if (!cropped_input_frame)
     return nullptr;
@@ skipping 24 matching lines @@
       return NULL;
     }
   } else {
     cropped_input_frame->StretchToFrame(output_frame_.get(), true, true);
     output_frame_->SetTimeStamp(cropped_input_frame->GetTimeStamp());
   }
   return output_frame_->Copy();
 }
 
 }  // namespace cricket