Handle Alpha channel in Canvas capture

content/renderer/media/video_track_recorder.cc

 // Copyright 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.
 
 #include "content/renderer/media/video_track_recorder.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/sys_info.h"
 #include "base/threading/thread.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "media/base/video_frame.h"
+#include "media/base/video_util.h"
 #include "ui/gfx/geometry/size.h"
 
 extern "C" {
 // VPX_CODEC_DISABLE_COMPAT excludes parts of the libvpx API that provide
 // backwards compatibility for legacy applications using the library.
 #define VPX_CODEC_DISABLE_COMPAT 1
 #include "third_party/libvpx_new/source/libvpx/vpx/vp8cx.h"
 #include "third_party/libvpx_new/source/libvpx/vpx/vpx_encoder.h"
 }
 
@@ skipping 152 matching lines @@
     origin_task_runner_ = base::MessageLoop::current()->task_runner();
   DCHECK(origin_task_runner_->BelongsToCurrentThread());
   if (paused_)
     return;
   encoding_thread_->task_runner()->PostTask(
       FROM_HERE, base::Bind(&VpxEncoder::EncodeOnEncodingThread,
                             this, frame, capture_timestamp));
 }
 
 void VideoTrackRecorder::VpxEncoder::EncodeOnEncodingThread(
-    const scoped_refptr<VideoFrame>& frame,
+    const scoped_refptr<VideoFrame>& video_frame,
     base::TimeTicks capture_timestamp) {
   TRACE_EVENT0("video",
                "VideoTrackRecorder::VpxEncoder::EncodeOnEncodingThread");
   DCHECK(encoding_thread_->task_runner()->BelongsToCurrentThread());
 
+  if (!(video_frame->format() == media::PIXEL_FORMAT_I420 ||
+        video_frame->format() == media::PIXEL_FORMAT_YV12 ||
+        video_frame->format() == media::PIXEL_FORMAT_YV12A)) {
+    NOTREACHED();
+    return;
+  }
+  scoped_refptr<media::VideoFrame> frame = video_frame;
+  // Drop alpha channel since we do not support it yet.
+  if (frame->format() == media::PIXEL_FORMAT_YV12A)
+    frame = media::WrapAsI420VideoFrame(video_frame);
+
   const gfx::Size frame_size = frame->visible_rect().size();
   if (!IsInitialized() ||
       gfx::Size(codec_config_.g_w, codec_config_.g_h) != frame_size) {
     ConfigureEncoding(frame_size);
   }
 
   vpx_image_t vpx_image;
   vpx_image_t* const result = vpx_img_wrap(&vpx_image,
                                            VPX_IMG_FMT_I420,
                                            frame_size.width(),
@@ skipping 196 matching lines @@
   encoder_->set_paused(false);
 }
 
 void VideoTrackRecorder::OnVideoFrameForTesting(
     const scoped_refptr<media::VideoFrame>& frame,
     base::TimeTicks timestamp) {
   encoder_->StartFrameEncode(frame, timestamp);
 }
 
 }  // namespace content