Add native handle support to SimulcastEncoderAdapter.

webrtc/modules/video_coding/codecs/vp8/simulcast_encoder_adapter.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.
  */
 
@@ skipping 271 matching lines @@
       streaminfos_[stream_idx].key_frame_request = false;
     } else {
       stream_frame_types.push_back(kVideoFrameDelta);
     }
 
     int dst_width = streaminfos_[stream_idx].width;
     int dst_height = streaminfos_[stream_idx].height;
     // If scaling isn't required, because the input resolution
     // matches the destination or the input image is empty (e.g.
     // a keyframe request for encoders with internal camera
-    // sources), pass the image on directly. Otherwise, we'll
-    // scale it to match what the encoder expects (below).
+    // sources) or the source image has a native handle, pass the image on
+    // directly. Otherwise, we'll scale it to match what the encoder expects
+    // (below).
+    // For texture frames, the underlying encoder is expected to be able to
+    // correctly sample/scale the source texture.
     if ((dst_width == src_width && dst_height == src_height) ||
-        input_image.IsZeroSize()) {
+        input_image.IsZeroSize() ||
+        input_image.video_frame_buffer()->native_handle()) {

[perkj_webrtc, 2016/06/27 08:02:01]

The encoder does not know the size is should scale too. 
Scaling is simple in it self, we just need to create a new VideoFrameBuffer with
the correct width and height. There is a plan to 
add a scale factor in the buffers to handle this 
https://bugs.chromium.org/p/webrtc/issues/detail?id=5683 but that is not done.
If this is not a problem today for hw encoders on Mac and Win I guess we can add
a TODO here and update the bug 5683. 

[noahric, 2016/06/30 17:17:39]

Added a TODO here with a reference for webrtc:5683. Let me know if that's ok
(assuming I submit before you see it, let me know and I'll fix it in a follow-up
CL).

       int ret = streaminfos_[stream_idx].encoder->Encode(
           input_image, codec_specific_info, &stream_frame_types);
       if (ret != WEBRTC_VIDEO_CODEC_OK) {
         return ret;
       }
     } else {
       VideoFrame dst_frame;

[perkj_webrtc, 2016/06/28 14:09:00]

So apparently no one use simulcast with native textures today so I think this is
fine but it might be good to add a comment that the native handles are not
scaled. 

There are two ways to handle this in the long run. Either the encoder must scale
textures to the encoder configured size. 
Bug webrtc::5683 suggest that a frame should contain a scale factor so that we
can postpone all scaling until we know that the frame actually will be encoded
and scaling should probably occur in the encoder. So here a new VideoFrameBuffer
with separate scale factors but with the same under laying data buffer could be
created.

When it comes to quality scaling it gets a bit confusing. What does it mean that
the quality scaler want to downscale a layer due to bad
quality?https://cs.chromium.org/chromium/src/third_party/webrtc/api/java/jni/androidmediaencoder_jni.cc?rcl=0&l=700.
In our android encoder implementation the frame size decide how the encoder
should be configured after quality scaling. 

[pbos-webrtc, 2016/06/29 15:48:27]

I think quality scaling should apply outside and just be fed into the encoder
with a new size. I assume that this encoder would then feel free to drop layers.

       // Making sure that destination frame is of sufficient size.
       // Aligning stride values based on width.
       dst_frame.CreateEmptyFrame(dst_width, dst_height, dst_width,
                                  (dst_width + 1) / 2, (dst_width + 1) / 2);
       libyuv::I420Scale(input_image.video_frame_buffer()->DataY(),
                         input_image.video_frame_buffer()->StrideY(),
                         input_image.video_frame_buffer()->DataU(),
                         input_image.video_frame_buffer()->StrideU(),
                         input_image.video_frame_buffer()->DataV(),
                         input_image.video_frame_buffer()->StrideV(),
@@ skipping 190 matching lines @@
   return !streaminfos_.empty();
 }
 
 void SimulcastEncoderAdapter::OnDroppedFrame() {
   streaminfos_[0].encoder->OnDroppedFrame();
 }
 
 bool SimulcastEncoderAdapter::SupportsNativeHandle() const {
   // We should not be calling this method before streaminfos_ are configured.
   RTC_DCHECK(!streaminfos_.empty());
-  // TODO(pbos): Support textures when using more than one encoder.
-  if (streaminfos_.size() != 1)
-    return false;
-  return streaminfos_[0].encoder->SupportsNativeHandle();
+  for (const auto& streaminfo : streaminfos_) {
+    if (!streaminfo.encoder->SupportsNativeHandle()) {
+      return false;

[pbos-webrtc, 2016/06/29 15:48:27]

remove {}s, you're not in Kansas anymore, cowboy.

[noahric, 2016/06/30 17:17:39]

Done :)

+    }
+  }
+  return true;
 }
 
 const char* SimulcastEncoderAdapter::ImplementationName() const {
   return implementation_name_.c_str();
 }
 
 }  // namespace webrtc