Prioritize video packets when sending padding or preemptive retransmits.

webrtc/video/video_send_stream.cc

Index: webrtc/video/video_send_stream.cc
diff --git a/webrtc/video/video_send_stream.cc b/webrtc/video/video_send_stream.cc
index 3b4238c47da00fe4c07a3654d2ecdf1a7bedd303..0e7d954c7009788ca1b9557359a561becb720df4 100644
--- a/webrtc/video/video_send_stream.cc
+++ b/webrtc/video/video_send_stream.cc
@@ -797,8 +797,13 @@ VideoSendStreamImpl::VideoSendStreamImpl(
       config_->periodic_alr_bandwidth_probing);
 
   // RTP/RTCP initialization.
-  for (RtpRtcp* rtp_rtcp : rtp_rtcp_modules_) {
-    packet_router_->AddRtpModule(rtp_rtcp);
+
+  // We add the highest spatial layer first to ensure it'll be prioritized
+  // when sending padding, with the hope that the packet rate will be smaller,

[mflodman, 2017/01/26 13:01:40]

Isn't this the opposite? AddRtpModule does a push_front -> the module added in
the end will be in the front and do all the padding.

[stefan-webrtc, 2017/01/27 11:52:38]

Yes, you are right. Thanks :)

+  // and that it's more important to protect than the lower layers.
+  for (auto rit = rtp_rtcp_modules_.rbegin(); rit != rtp_rtcp_modules_.rend();
+       ++rit) {
+    packet_router->AddRtpModule(*rit);
   }
 
   for (size_t i = 0; i < config_->rtp.extensions.size(); ++i) {