Enable vp9 row-based multithreading.

webrtc/modules/video_coding/codecs/vp9/vp9_impl.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 431 matching lines @@
       VP9EncoderImpl::EncoderOutputCodedPacketCallback,
       reinterpret_cast<void*>(this)};
   vpx_codec_control(encoder_, VP9E_REGISTER_CX_CALLBACK,
                     reinterpret_cast<void*>(&cbp));
 
   // Control function to set the number of column tiles in encoding a frame, in
   // log2 unit: e.g., 0 = 1 tile column, 1 = 2 tile columns, 2 = 4 tile columns.
   // The number tile columns will be capped by the encoder based on image size
   // (minimum width of tile column is 256 pixels, maximum is 4096).
   vpx_codec_control(encoder_, VP9E_SET_TILE_COLUMNS, (config_->g_threads >> 1));
+
+  // Turn on row-based multithreading.
+  vpx_codec_control(encoder_, VP9E_SET_ROW_MT, 1);
 #if !defined(WEBRTC_ARCH_ARM) && !defined(WEBRTC_ARCH_ARM64) && \
   !defined(ANDROID)
   // Note denoiser is still off by default until further testing/optimization,
   // i.e., VP9().denoisingOn == 0.
   vpx_codec_control(encoder_, VP9E_SET_NOISE_SENSITIVITY,
                     inst->VP9().denoisingOn ? 1 : 0);
 #endif
   if (codec_.mode == kScreensharing) {
     // Adjust internal parameters to screen content.
     vpx_codec_control(encoder_, VP9E_SET_TUNE_CONTENT, 1);
@@ skipping 540 matching lines @@
   frame_buffer_pool_.ClearPool();
   inited_ = false;
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
 const char* VP9DecoderImpl::ImplementationName() const {
   return "libvpx";
 }
 
 }  // namespace webrtc