[webrtc-pc] Clarify "multiple sources of media **stitched together**" at Note describing replaceTrack (#2171)

guest271314 has just created a new issue for https://github.com/w3c/webrtc-pc:

== Clarify "multiple sources of media **stitched together**" at Note describing replaceTrack ==


1) Am consider composing a PR for another W3C repository (MediaRecorder) which will prospectively use language contained in this W3C repository; the description of replaceTrack() https://w3c.github.io/webrtc-pc/#dom-rtcrtpsender-replacetrack, particularly 

> 6.4.3 If sending is true, and withTrack is not null, have the sender switch seamlessly to transmitting withTrack instead of the sender's existing track.

2) When reading content in this specification relating to `replaceTrack()` there is a note at https://w3c.github.io/webrtc-pc/#dom-rtcrtpsender-replacetrack#issue-container-generatedID-29

> NOTE
> 
> There is not an exact 1:1 correspondence between tracks sent by one RTCPeerConnection and received by the other. For one, IDs of tracks sent have no mapping to the IDs of tracks received. Also, replaceTrack changes the track sent by an RTCRtpSender without creating a new track on the receiver side; the corresponding RTCRtpReceiver will only have a single track, potentially representing **multiple sources of media stitched together**. Both addTransceiver and replaceTrack can be used to cause the same track to be sent multiple times, which will be observed on the receiver side as multiple receivers each with its own separate track. Thus it's more accurate to think of a 1:1 relationship between an RTCRtpSender on one side and an RTCRtpReceiver's track on the other side, matching senders and receivers using the RTCRtpTransceiver's mid if necessary. (emphasis added)

where the term "multiple sources of media stitched together" is used. The specification does not clarify that procedure. Is using some of the above language (read https://www.w3.org/Consortium/Legal/2015/doc-license) in this specification in a PR for another W3C repository/specification ok; if so, does this specification need to be cited?

2) For the purpose of avoiding confusion as to precisely what the PR is describing can this specification clarify what "stitched together" technically means and if the specification defines the procedure to stitch together "multiple sources of media"?

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/2171 using your GitHub account

Received on Saturday, 13 April 2019 21:16:23 UTC