286358 2025-01-22 07:13:50 -0800 Sender priority settings set when adding tracks to an RTC Peer Connection are ignored 2025-11-06 13:52:58 -0800 1 1 1 Unclassified WebKit WebRTC Safari 18 Mac (Apple Silicon) macOS 15 NEW InRadar P2 Normal --- 1 marco webkit-unassigned h webkit-bug-importer youennf oldest_to_newest 2088977 0 marco 2025-01-22 07:13:50 -0800 The JS API in Safari supports setting `parameters.encodings.priority` via `RTCRtpSender.setParameters()` (see https://developer.mozilla.org/en-US/docs/Web/API/RTCRtpSender/setParameters#browser_compatibility). However, the RTP packets that are actually sent by Safari always contain a default priority header, regardless of what priority is being set via JS. To reproduce: - Establish a WebRTC Peer connection between 2 peers - Create a Media Stream, for example by getting access to user media with `getUserMedia()` - For each track of the media stream, add it to the peer connection and update its parameter encodings by setting priority to 'high': stream.getTracks().forEach((track) => { let sender = this._connection.addTrack(track, stream); const params = sender.getParameters(); params.encodings = params.encodings.map((e) => { if (e.priority) { e.priority = 'high'; } if (e.networkPriority) { e.networkPriority = 'high'; } return e; }); sender.setParameters(params); }); - Capture the packets using Wireshark and inspect the packet headers. Expected behaviour The packet header under IPv4 > Differentiated Services Field should be set to "Expedited Forwarding (46)". Actual behaviour The packet header is set to "Default (0)". Related issue: https://bugs.webkit.org/show_bug.cgi?id=277605 For more context on the use of the priority encodings and the effects of the bug, see: https://github.com/versatica/JsSIP/pull/893 2090430 1 webkit-bug-importer 2025-01-29 07:14:16 -0800 <rdar://problem/143820797>