RESOLVED DUPLICATE of bug 292273292858
Wrong WebRTC H264 video clock rate since Safari 18.4.1 
https://bugs.webkit.org/show_bug.cgi?id=292858
Summary Wrong WebRTC H264 video clock rate since Safari 18.4.1
mgookov
Reported 2025-05-12 03:50:47 PDT
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.
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youenn fablet
Comment 1 2025-05-13 04:53:29 PDT
This is likely https://bugs.webkit.org/show_bug.cgi?id=292273.
youenn fablet
Comment 2 2025-05-13 04:53:41 PDT
*** This bug has been marked as a duplicate of bug 292273 ***
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