Disallow simulcast for non-vp8.

talk/media/webrtc/webrtcvideoengine2.cc

 /*
  * libjingle
  * Copyright 2014 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 285 matching lines @@
   if (other.red_rtx_payload_type != -1) {
     if (output->red_rtx_payload_type != -1 &&
         output->red_rtx_payload_type != other.red_rtx_payload_type) {
       LOG(LS_WARNING) << "Conflict merging red_rtx_payload_type configs: "
                       << output->red_rtx_payload_type << " and "
                       << other.red_rtx_payload_type;
     }
     output->red_rtx_payload_type = other.red_rtx_payload_type;
   }
 }
+
+// Returns true if the given codec is disallowed from doing simulcast.
+bool IsCodecBlacklistedForSimulcast(const std::string& codec_name) {
+  return CodecNamesEq(codec_name, kH264CodecName);
+}
+
 }  // namespace
 
 // Constants defined in talk/media/webrtc/constants.h
 // TODO(pbos): Move these to a separate constants.cc file.
 const int kMinVideoBitrate = 30;
 const int kStartVideoBitrate = 300;
 const int kMaxVideoBitrate = 2000;
 
 const int kVideoMtu = 1200;
 const int kVideoRtpBufferSize = 65536;
@@ skipping 1776 matching lines @@
     if (codec.width < width)
       width = codec.width;
     if (codec.height < height)
       height = codec.height;
   }
 
   VideoCodec clamped_codec = codec;
   clamped_codec.width = width;
   clamped_codec.height = height;
 
-  encoder_config.streams = CreateVideoStreams(
-      clamped_codec, parameters_.options, parameters_.max_bitrate_bps,
-      dimensions.is_screencast ? 1 : parameters_.config.rtp.ssrcs.size());
+  // By default, the stream count for the codec configuration should match the
+  // number of negotiated ssrcs. But if the codec is blacklisted for simulcast
+  // or a screencast, only configure a single stream.
+  size_t stream_count = parameters_.config.rtp.ssrcs.size();
+  if (IsCodecBlacklistedForSimulcast(codec.name) || dimensions.is_screencast) {
+    stream_count = 1;
+  }
+
+  encoder_config.streams =
+      CreateVideoStreams(clamped_codec, parameters_.options,
+                         parameters_.max_bitrate_bps, stream_count);
 
   // Conference mode screencast uses 2 temporal layers split at 100kbit.
   if (parameters_.options.conference_mode.GetWithDefaultIfUnset(false) &&
       dimensions.is_screencast && encoder_config.streams.size() == 1) {
     ScreenshareLayerConfig config = ScreenshareLayerConfig::GetDefault();
 
     // For screenshare in conference mode, tl0 and tl1 bitrates are piggybacked
     // on the VideoCodec struct as target and max bitrates, respectively.
     // See eg. webrtc::VP8EncoderImpl::SetRates().
     encoder_config.streams[0].target_bitrate_bps =
@@ skipping 607 matching lines @@
       video_codecs[i].rtx_payload_type = rtx_mapping[video_codecs[i].codec.id];
     }
   }
 
   return video_codecs;
 }
 
 }  // namespace cricket
 
 #endif  // HAVE_WEBRTC_VIDEO