[WEBRTC] Handling of RTX

Previous notes, finishing

WEBRTC in the default open RTX for packet loss retransmission, the introduction of RTX can refer to Rfc4588,https://tools.ietf.org/html/rfc4588#section-4

RTX uses an additional SSRC transmission, SSRC is identified in the SDP.

↵a=rtpmap: rtx/90000↵a2736695910239189782

Like this.

A RTX packet, in Turnserver, is such that the raw UDP data->turn/stun protocol header->RTP Header1->RTP header2

In RTP header1, according to payload type to distinguish RTP, RTX data, if it is rtx, you need to SRTP to solve the subsequent data, and then parse.

In the client, the key functions of the RTX packets are:

HTTPS://code.google.com/p/webrtc/source/detail?r=4692channel::i Spacketretransmittedchannel::handlertxpacketrtp_payload_registry_, Isrtxrtppayloadregistry:: Restoreoriginalpacket    Remove the RTX header and restore the original RTP

Link Yes, WEBRTC join RTX issue

Currently WEBRTC servers, such as Licode,janus, are prohibited from RTX. To avoid complex processing.

[WEBRTC] Handling of RTX