In the https://w3c.github.io/webrtc-extensions/ we define the captureTimestamp and senderCaptureTimeOffset at contribution source level, however this information is available on a per frame level too.
I believe it would be interesting to be able to expose the same both values in the RTCEncodedAudioFrameMetadata and RTCEncodedVideoFrameMetadata when the abs capture time header extension is used.
Related: PR 137