--- a/media/webrtc/signaling/src/jsep/JsepSessionImpl.cpp
+++ b/media/webrtc/signaling/src/jsep/JsepSessionImpl.cpp
@@ -333,17 +333,17 @@ JsepSessionImpl::SetParameters(const std
         default: {
           MOZ_ASSERT(false);
           return NS_ERROR_INVALID_ARG;
         }
       }
     }
   }
   if (addVideoExt != SdpDirectionAttribute::kInactive) {
-    AddVideoRtpExtension("urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id", addVideoExt);
+    AddVideoRtpExtension(webrtc::RtpExtension::kRtpStreamIdUri, addVideoExt);
   }
 
   it->mTrack->SetJsConstraints(constraints);
 
   auto track = it->mTrack;
   if (track->GetDirection() == sdp::kSend) {
     // Establish minimum number of required SSRCs
     // Note that AddTrack is only for send direction
@@ -2382,22 +2382,21 @@ JsepSessionImpl::SetupDefaultCodecs()
   // Update the redundant encodings for the RED codec with the supported
   // codecs.  Note: only uses the video codecs.
   red->UpdateRedundantEncodings(mSupportedCodecs.values);
 }
 
 void
 JsepSessionImpl::SetupDefaultRtpExtensions()
 {
-  AddAudioRtpExtension("urn:ietf:params:rtp-hdrext:ssrc-audio-level",
+  AddAudioRtpExtension(webrtc::RtpExtension::kAudioLevelUri,
                        SdpDirectionAttribute::Direction::kSendonly);
-  AddVideoRtpExtension(
-    "http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time",
+  AddVideoRtpExtension(webrtc::RtpExtension::kAbsSendTimeUri,
                        SdpDirectionAttribute::Direction::kSendrecv);
-  AddVideoRtpExtension("urn:ietf:params:rtp-hdrext:toffset",
+  AddVideoRtpExtension(webrtc::RtpExtension::kTimestampOffsetUri,
                        SdpDirectionAttribute::Direction::kSendrecv);
 }
 
 void
 JsepSessionImpl::SetState(JsepSignalingState state)
 {
   if (state == mState)
     return;

--- a/media/webrtc/signaling/src/peerconnection/MediaPipelineFactory.cpp
+++ b/media/webrtc/signaling/src/peerconnection/MediaPipelineFactory.cpp
@@ -744,17 +744,17 @@ MediaPipelineFactory::GetOrCreateAudioCo
     auto error = conduit->ConfigureSendMediaCodec(configs.values[0]);
     if (error) {
       MOZ_MTLOG(ML_ERROR, "ConfigureSendMediaCodec failed: " << error);
       return NS_ERROR_FAILURE;
     }
 
     const SdpExtmapAttributeList::Extmap* audioLevelExt =
         aTrack.GetNegotiatedDetails()->GetExt(
-            "urn:ietf:params:rtp-hdrext:ssrc-audio-level");
+            webrtc::RtpExtension::kAudioLevelUri);
 
     if (audioLevelExt) {
       MOZ_MTLOG(ML_DEBUG, "Calling EnableAudioLevelExtension");
       error = conduit->EnableAudioLevelExtension(true, audioLevelExt->entry);
 
       if (error) {
         MOZ_MTLOG(ML_ERROR, "EnableAudioLevelExtension failed: " << error);
         return NS_ERROR_FAILURE;