Configure OpenH264 sSliceArgument.uiSliceNum set to 1.

webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc

 /*
  *  Copyright (c) 2015 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 421 matching lines @@
   encoder_params.iMultipleThreadIdc = NumberOfThreads(
       encoder_params.iPicWidth, encoder_params.iPicHeight, number_of_cores_);
   // The base spatial layer 0 is the only one we use.
   encoder_params.sSpatialLayers[0].iVideoWidth = encoder_params.iPicWidth;
   encoder_params.sSpatialLayers[0].iVideoHeight = encoder_params.iPicHeight;
   encoder_params.sSpatialLayers[0].fFrameRate = encoder_params.fMaxFrameRate;
   encoder_params.sSpatialLayers[0].iSpatialBitrate =
       encoder_params.iTargetBitrate;
   encoder_params.sSpatialLayers[0].iMaxSpatialBitrate =
       encoder_params.iMaxBitrate;
+  // Slice num according to number of threads.
 #if (OPENH264_MAJOR == 1) && (OPENH264_MINOR <= 5)
-  // Slice num according to number of threads.
   encoder_params.sSpatialLayers[0].sSliceCfg.uiSliceMode = SM_AUTO_SLICE;
 #else
-  // When uiSliceMode = SM_FIXEDSLCNUM_SLICE, uiSliceNum = 0 means auto design
-  // it with cpu core number.
-  encoder_params.sSpatialLayers[0].sSliceArgument.uiSliceNum = 0;
+  encoder_params.sSpatialLayers[0].sSliceArgument.uiSliceNum =
+      encoder_params.iMultipleThreadIdc;

[hbos, 2016/10/28 09:01:03]

Do we know that n works if number of threads are n>1? I.e, should this be 1 or
n? In either case we'll notice when n changes from hard-coded 1.

[sprang_webrtc, 2016/10/31 09:22:29]

I tried with 4 thread and uiSliceNum 4 and the rate controller is still borked.
Hard-coding to 1 instead and adding todo about following up on seeming OpenH264
bug.

[hbos, 2016/10/31 09:23:33]

sgtm

   encoder_params.sSpatialLayers[0].sSliceArgument.uiSliceMode =
       SM_FIXEDSLCNUM_SLICE;
 #endif
 
   return encoder_params;
 }
 
 void H264EncoderImpl::ReportInit() {
   if (has_reported_init_)
     return;
@@ skipping 19 matching lines @@
 
 int32_t H264EncoderImpl::SetPeriodicKeyFrames(bool enable) {
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
 void H264EncoderImpl::OnDroppedFrame() {
   quality_scaler_.ReportDroppedFrame();
 }
 
 }  // namespace webrtc