Stop caching supported codecs in WebRtcVideoEngine2

webrtc/pc/channelmanager.cc

Index: webrtc/pc/channelmanager.cc
diff --git a/webrtc/pc/channelmanager.cc b/webrtc/pc/channelmanager.cc
index 06475e9eaa26f13ec0883a1c8e8654675cbf8e9e..fb6f44f846d7acf50543ec83f491a22a84bc5b80 100644
--- a/webrtc/pc/channelmanager.cc
+++ b/webrtc/pc/channelmanager.cc
@@ -29,6 +29,9 @@
 
 namespace cricket {
 
+static bool IsRtxCodec(const VideoCodec& codec) {
+  return _stricmp(kRtxCodecName, codec.name.c_str()) == 0;

[tommi, 2016/11/09 16:24:30]

in tests, we have case sensitive comparisons for this codec name. Outside of
tests we have stricmp in a couple of places (looks like you're copying one
here), but in SdpAudioFormat we actually have a case sensitive comparison when
we do lookups.

Can you check with Harald to see what is the right thing to be doing?  I suspect
case sensitive is what we want.  If so, you could replace IsRtxCodec with simply
codec.name.compare(kRtxCodecName) == 0

Btw, there are also macros for doing case sensitive and case insensitive string
compare.  See STR_NCASE_CMP.

[magjed_webrtc, 2016/11/09 20:37:53]

Ok, I will ask hta@ for advice. The code here is just moved from the existing
code at line 147, but it might be wrong.

Regarding std::string::compare, won't that create a temporary std::string out of
the kRtxCodecName (char*), which will hurt performance?

[tommi, 2016/11/09 20:59:50]

There's a version of compare() that takes a const char*, so the performance
should be the same as with strcmp.

[magjed_webrtc, 2016/11/09 21:15:10]

Ah cool, I missed that.

+}
 
 using rtc::Bind;
 
@@ -137,18 +140,13 @@ void ChannelManager::GetSupportedAudioRtpHeaderExtensions(
   *ext = media_engine_->GetAudioCapabilities().header_extensions;
 }
 
-void ChannelManager::GetSupportedVideoCodecs(
-    std::vector<VideoCodec>* codecs) const {
-  codecs->clear();
-
-  std::vector<VideoCodec>::const_iterator it;
-  for (it = media_engine_->video_codecs().begin();
-      it != media_engine_->video_codecs().end(); ++it) {
-    if (!enable_rtx_ && _stricmp(kRtxCodecName, it->name.c_str()) == 0) {
-      continue;
-    }
-    codecs->push_back(*it);
+std::vector<VideoCodec> ChannelManager::GetSupportedVideoCodecs() const {
+  std::vector<VideoCodec> codecs = media_engine_->video_codecs();
+  if (!enable_rtx_) {
+    codecs.erase(std::remove_if(codecs.begin(), codecs.end(), &IsRtxCodec),
+                 codecs.end());
   }
+  return codecs;
 }
 
 void ChannelManager::GetSupportedVideoRtpHeaderExtensions(