292858 2025-05-12 03:50:47 -0700 Wrong WebRTC H264 video clock rate since Safari 18.4.1 2025-05-13 04:53:41 -0700 1 1 1 Unclassified WebKit WebRTC Safari 18 iPhone / iPad iOS 18 RESOLVED DUPLICATE 292273 P2 Normal --- 1 mgookov webkit-unassigned glendonwalkerii youennf oldest_to_newest 2116444 0 mgookov 2025-05-12 03:50:47 -0700 When I publish video from my iPhone (Safari 18.4.1) (or macOS) via a WebRTC (RTP), the server receives a packet with a timestamp frequency(clock rate) of 900 kHz instead of 90 kHz. SDP example a=mid:1 a=rtpmap:96 H264/90000 a=fmtp:96 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=640c1f a=rtcp-fb:96 ccm fir a=rtcp-fb:96 nack a=rtcp-fb:96 nack pli a=rtcp-fb:96 goog-remb a=rtpmap:98 H264/90000 a=fmtp:98 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f a=rtcp-fb:98 ccm fir a=rtcp-fb:98 nack a=rtcp-fb:98 nack pli a=rtcp-fb:98 goog-remb a=rtpmap:100 H264/90000 a=fmtp:100 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=640c1f a=rtcp-fb:100 ccm fir a=rtcp-fb:100 nack a=rtcp-fb:100 nack pli a=rtcp-fb:100 goog-remb a=rtpmap:102 H264/90000 a=fmtp:102 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42e01f a=rtcp-fb:102 ccm fir a=rtcp-fb:102 nack a=rtcp-fb:102 nack pli a=rtcp-fb:102 goog-remb Example of received packets (H264, 30 fps): sn=1157, timestamp=4133632481 sn=1158, timestamp=4133632481 sn=1159, timestamp=4133632481 sn=1160, timestamp=4133632481 sn=1161, timestamp=4133632481 sn=1162, timestamp=4133665095 sn=1163, timestamp=4133665095 sn=1164, timestamp=4133665095 sn=1165, timestamp=4133665095 sn=1166, timestamp=4133665095 sn=1167, timestamp=4133699279 sn=1168, timestamp=4133699279 sn=1169, timestamp=4133699279 sn=1170, timestamp=4133699279 sn=1171, timestamp=4133699279 sn=1172, timestamp=4133731294 sn=1173, timestamp=4133731294 sn=1174, timestamp=4133731294 sn=1175, timestamp=4133731294 sn=1176, timestamp=4133731294 The diff between frame timestamps is about 32000. The same for SenderReport. If I use clock rate = 900 kHz, audio/video synchronization is good, with 90 kHz it doesn't work. 2116729 1 youennf 2025-05-13 04:53:29 -0700 This is likely https://bugs.webkit.org/show_bug.cgi?id=292273. 2116730 2 youennf 2025-05-13 04:53:41 -0700 *** This bug has been marked as a duplicate of bug 292273 ***