RE: [webrtc-pc] Need to specify which members of the encodings in "sendEncodings" are actually used

The table in Section 5.2 describes which RTCRtpEncodings dictionary members apply to RtpReceiver/RtpSender and which are Read/Write versus Read-only:


Attribute

Type

Receiver/Sender

Read/Write

ssrc

unsigned long

Receiver/Sender

Read-only

fec

RTCRtpFecParameters<https://rawgit.com/w3c/webrtc-pc/master/webrtc.html#dom-rtcrtpfecparameters>

Receiver/Sender

Read-only

dtx

RTCDtxStatus<https://rawgit.com/w3c/webrtc-pc/master/webrtc.html#dom-rtcdtxstatus>

Sender

Read/Write

rtx

RTCRtpRtxParameters<https://rawgit.com/w3c/webrtc-pc/master/webrtc.html#dom-rtcrtprtxparameters>

Receiver/Sender

Read-only

active

boolean

Sender

Read/Write

priority

RTCPriorityType<https://rawgit.com/w3c/webrtc-pc/master/webrtc.html#dom-rtcprioritytype>

Sender

Read/Write

maxBitrate

unsigned long

Sender

Read/Write

maxFramerate

unsigned long

Sender

Read/Write

scaleResolutionDownBy

double

Sender

Read/Write

rid

DOMString

Receiver/Sender

Read-only




Since setParameters() cannot set the “negotiation-needed” flag, members that are Read/Write cannot affect the SDP generated in an offer (or answer).



This leaves only rid, rtx, fec and ssrc as possibilities that could affect the offer SDP.  Since in WebRTC RTCRtpRtxParameters and RTCRtpFecParameters only contain ssrc as a member, if we don’t let the application choose ssrcs, that leaves only the rid.



Perhaps we need another column in the table to clarify this?





-----Original Message-----
From: Taylor Brandstetter via GitHub [mailto:sysbot+gh@w3.org]
Sent: Monday, March 13, 2017 4:14 PM
To: public-webrtc@w3.org
Subject: [webrtc-pc] Need to specify which members of the encodings in "sendEncodings" are actually used



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




== Need to specify which members of the encodings in "sendEncodings" are actually used == The description of the `sendEncodings` member of `RTCRtpTransceiverInit` is currently:



> A sequence containing parameters for sending RTP encodings of media.



This somewhat implies that the full contents of the `RTCRtpEncodingParameters` are processed and used when generating an offer. But the only member that appears used by JSEP is `rid`. If this is correct, it should be clarified somewhere, either in the description of `sendEncodings` or in the `addTransceiver` steps.



Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/1073 using your GitHub account