Make WebRTC compatible with OpenH264 v1.6.

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

Index: webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc
diff --git a/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc b/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc
index 3dfa0b559d1228725ae8820bbb0f2aecd551b410..56b88b1276d3059d332dd8047056a78c0d66c9a0 100644
--- a/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc
+++ b/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc
@@ -16,6 +16,7 @@
 #include "third_party/openh264/src/codec/api/svc/codec_api.h"
 #include "third_party/openh264/src/codec/api/svc/codec_app_def.h"
 #include "third_party/openh264/src/codec/api/svc/codec_def.h"
+#include "third_party/openh264/src/codec/api/svc/codec_ver.h"
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
@@ -149,6 +150,7 @@ static void RtpFragmentize(EncodedImage* encoded_image,
 
 H264EncoderImpl::H264EncoderImpl()
     : openh264_encoder_(nullptr),
+      number_of_cores_(0),
       encoded_image_callback_(nullptr),
       has_reported_init_(false),
       has_reported_error_(false) {
@@ -439,7 +441,12 @@ SEncParamExt H264EncoderImpl::CreateEncoderParams() const {
   encoder_params.sSpatialLayers[0].iMaxSpatialBitrate =
       encoder_params.iMaxBitrate;
   // Slice num according to number of threads.
+#if (OPENH264_MAJOR == 1) && (OPENH264_MINOR <= 5)
   encoder_params.sSpatialLayers[0].sSliceCfg.uiSliceMode = SM_AUTO_SLICE;
+#else
+  encoder_params.sSpatialLayers[0].sSliceArgument.uiSliceMode =
+      SM_FIXEDSLCNUM_SLICE;

[stefan-webrtc, 2016/10/24 10:42:02]

Maybe comment on what this means? Reading the header file it seems to mean that
it will use the appropriate number of slices to achieve good multi-threading.
The slices are not optimized for bitstream robustness.

https://github.com/cisco/openh264/blob/997f0ed69b811697611fceb2d12ca8cfe42352...

[sprang_webrtc, 2016/10/24 11:28:19]

Comment above still says "// Slice num according to number of threads."? :)

[hbos_chromium, 2016/10/24 14:10:37]

According to the link, SM_FIXEDSLCNUM_SLICE sets it in accordance with SliceNum
(SSliceArgument::uiSliceNum). Since we don't set
sSpatialLayers[0].sSliceArgument it would use its default value, which I believe
is 0,
https://github.com/cisco/openh264/blob/997f0ed69b811697611fceb2d12ca8cfe42352....
"uiSliceNum=0 means auto design it with cpu core number".

So this should be auto. Up to you if you want to explicitly set it to 0 and add
a comment saying it is based on the number of cores.

+#endif
 
   return encoder_params;
 }