medoozeWebRTC Semantic SDP
Minimal SDP information semantic data model and parsing tools.
Motivation
Have you ever tried to mangle or process an SDP and got stuck about how to you change the information instead of what information do you want to access?
This project provies an abstraction layer on top of SDP that allows to acces and modify the information semantically, that is, it stores the SDP information and their relationships and allows you to get free of the acutal SDP semantics.
As it is meant to be used on WebRTC to WebRTC scenarios, so some SDP information can be safelly ignored, allowing to provide a simple and intuitive API.
Both Unified and Plan B are currently supported
Assumptions
We assume that:
- Bundle is used
- Trickle ICE or ICE lite is used
- DTLS is used
- RTCP mux is used
For the future
If you think it further exchanging the SDP information is all that it is needed to perform a peer to peer SDP exchange, so the intention is to provide serialization functions to be able to use this over the wire and only parse/serialize it on the endpoints or server side.
Note also that there is some similarity ORTC RTP parameters, but well done ;)
Install
npm i --save semantic-sdpUsage
const SemanticSDP = require('semantic-sdp');API Documention
You can check the full object documentation here.
Example
const SemanticSDP = require("semantic-sdp");
//Process the sdp
var offer = SemanticSDP.SDPInfo.process(sdp);
//Set the local DTLS and ICE info
const dtls = new DTLSInfo(Setup.PASSIVE,"sha-256","F2:AA:0E:C3:22:59:5E:14:95:69:92:3D:13:B4:84:24:2C:C2:A2:C0:3E:FD:34:8E:5E:EA:6F:AF:52:CE:E6:0F");
const ice = new ICEInfo("af46F","a34FasdS++jdfofdslkjsd/SDV");
//Get local candidte
const candidate = new CandidateInfo(1,1, "udp", 2122260223, "192.168.0.196", 56143, "host");
//Create local SDP info
let answer = new SDPInfo();
//Add ice and dtls info
answer.setDTLS(dtls);
answer.setICE(ice);
answer.addCandidate(candidate);
//Get remote audio m-line info
let audioOffer = offer.getMedia("audio");
//If we have audio
if (audioOffer)
{
//Create audio media
let audio = new MediaInfo("audio", "audio");
//Get codec type
let opus = audioOffer.getCodec("opus");
//Add opus codec
audio.addCodec(opus);
//Add audio extensions
for (let extension of audioOffer.getExtensions().entries())
//Add it
audio.addExtension(extension[0], extension[1]);
//Add it to answer
answer.addMedia(audio);
}
//Get remote video m-line info
let videoOffer = offer.getMedia("video");
//If offer had video
if (videoOffer)
{
//Create video media
let video = new MediaInfo("video", "video");
//Get codec types
let vp9 = videoOffer.getCodec("vp9");
let fec = videoOffer.getCodec("flexfec-03");
//Add video codecs
video.addCodec(vp9);
if (fec)
video.addCodec(fec);
//Limit incoming bitrate
video.setBitrate(1024);
//Add video extensions
for (let extension of videoOffer.getExtensions().entries())
//Add it
video.addExtension(extension[0], extension[1]);
//Add it to answer
answer.addMedia(video);
}
let ssrc = 1000;
//For each stream
for (let i=1;i<4;i++)
{
let track;
//Create stream
let stream = new StreamInfo("sream"+i);
//Create track
track = new TrackInfo("video", "track1");
//Get ssrc, rtx and fec
const media = ssrc++;
const rtx = ssrc++;
const fec = ssrc++;
//Add ssrcs to track
track.addSSRC(media);
track.addSSRC(rtx);
track.addSSRC(fec);
//Add RTX and FEC group
track.addSourceGroup(new SourceGroupInfo("FID",[media,rtx]));
track.addSourceGroup(new SourceGroupInfo("FEC-FR",[media,fec]));
//Add it
stream.addTrack(track);
//Create track
track = new TrackInfo("audio", "track2");
//Add ssrc
track.addSSRC(ssrc++);
//Add it
stream.addTrack(track);
//Add stream
answer.addStream(stream);
}
//Get answer SDP
const str = answer.toString();
const json = JSON.stringifu(answer.plain());The SDP output will be :
v=0
o=- 1489500633629 1 IN IP4 127.0.0.1
s=semantic-sdp
c=IN IP4 0.0.0.0
t=0 0
a=msid-semantic: WMS *
m=audio 9 UDP/TLS/RTP/SAVPF 111
a=rtpmap:111 opus/48000/2
a=rtcp-fb:111 transport-cc
a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level
a=setup:passive
a=mid:audio
a=sendrecv
a=ice-ufrag:af46F
a=ice-pwd:a34FasdS++jdfofdslkjsd/SDV
a=fingerprint:sha-256 F2:AA:0E:C3:22:59:5E:14:95:69:92:3D:13:B4:84:24:2C:C2:A2:C0:3E:FD:34:8E:5E:EA:6F:AF:52:CE:E6:0F
a=candidate:1 1 udp 2122260223 192.168.0.196 56143 typ host
a=ssrc:1003 cname:sream1
a=ssrc:1003 msid:sream1 track2
a=ssrc:1007 cname:sream2
a=ssrc:1007 msid:sream2 track2
a=ssrc:1011 cname:sream3
a=ssrc:1011 msid:sream3 track2
a=rtcp-mux
a=rtcp-rsize
m=video 9 UDP/TLS/RTP/SAVPF 98 99 125
b=AS:1024
a=rtpmap:98 VP9/90000
a=rtpmap:99 rtx/90000
a=rtpmap:125 flexfec-03/90000
a=fmtp:99 apt=98
a=rtcp-fb:98 transport-cc
a=rtcp-fb:125 transport-cc
a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=extmap:4 urn:3gpp:video-orientation
a=extmap:5 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01
a=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay
a=setup:passive
a=mid:video
a=sendrecv
a=ice-ufrag:af46F
a=ice-pwd:a34FasdS++jdfofdslkjsd/SDV
a=fingerprint:sha-256 F2:AA:0E:C3:22:59:5E:14:95:69:92:3D:13:B4:84:24:2C:C2:A2:C0:3E:FD:34:8E:5E:EA:6F:AF:52:CE:E6:0F
a=candidate:1 1 udp 2122260223 192.168.0.196 56143 typ host
a=ssrc:1000 cname:sream1
a=ssrc:1000 msid:sream1 track1
a=ssrc:1001 cname:sream1
a=ssrc:1001 msid:sream1 track1
a=ssrc:1002 cname:sream1
a=ssrc:1002 msid:sream1 track1
a=ssrc:1004 cname:sream2
a=ssrc:1004 msid:sream2 track1
a=ssrc:1005 cname:sream2
a=ssrc:1005 msid:sream2 track1
a=ssrc:1006 cname:sream2
a=ssrc:1006 msid:sream2 track1
a=ssrc:1008 cname:sream3
a=ssrc:1008 msid:sream3 track1
a=ssrc:1009 cname:sream3
a=ssrc:1009 msid:sream3 track1
a=ssrc:1010 cname:sream3
a=ssrc:1010 msid:sream3 track1
a=ssrc-group:FID 1000 1001
a=ssrc-group:FEC-FR 1000 1002
a=ssrc-group:FID 1004 1005
a=ssrc-group:FEC-FR 1004 1006
a=ssrc-group:FID 1008 1009
a=ssrc-group:FEC-FR 1008 1010
a=rtcp-mux
a=rtcp-rsizeAnd the serialized JSON string:
{
"version": 1,
"streams": [
{
"tracks": [
{
"media": "video",
"id": "track1",
"ssrcs": [
1000,
1001,
1002
],
"groups": [
{
"semantics": "FID",
"ssrcs": [
1000,
1001
]
},
{
"semantics": "FEC-FR",
"ssrcs": [
1000,
1002
]
}
]
},
{
"media": "audio",
"id": "track2",
"ssrcs": [
1003
],
"groups": [
]
}
]
},
{
"tracks": [
{
"media": "video",
"id": "track1",
"ssrcs": [
1004,
1005,
1006
],
"groups": [
{
"semantics": "FID",
"ssrcs": [
1004,
1005
]
},
{
"semantics": "FEC-FR",
"ssrcs": [
1004,
1006
]
}
]
},
{
"media": "audio",
"id": "track2",
"ssrcs": [
1007
],
"groups": [
]
}
]
},
{
"tracks": [
{
"media": "video",
"id": "track1",
"ssrcs": [
1008,
1009,
1010
],
"groups": [
{
"semantics": "FID",
"ssrcs": [
1008,
1009
]
},
{
"semantics": "FEC-FR",
"ssrcs": [
1008,
1010
]
}
]
},
{
"media": "audio",
"id": "track2",
"ssrcs": [
1011
],
"groups": [
]
}
]
}
],
"medias": [
{
"type": "audio",
"direction": "sendrecv",
"extensions": {
"1": "urn:ietf:params:rtp-hdrext:ssrc-audio-level"
},
"codecs": [
{
"codec": "opus",
"type": 111,
"params": {
"minptime": "10",
"useinbandfec": "1"
}
}
]
},
{
"type": "video",
"direction": "sendrecv",
"extensions": {
"2": "urn:ietf:params:rtp-hdrext:toffset",
"3": "http:\/\/www.webrtc.org\/experiments\/rtp-hdrext\/abs-send-time",
"4": "urn:3gpp:video-orientation",
"5": "http:\/\/www.ietf.org\/id\/draft-holmer-rmcat-transport-wide-cc-extensions-01",
"6": "http:\/\/www.webrtc.org\/experiments\/rtp-hdrext\/playout-delay"
},
"codecs": [
{
"codec": "VP9",
"type": 98,
"params": {
}
},
{
"codec": "flexfec-03",
"type": 125,
"params": {
"repair-window": "10000000"
}
}
],
"bitrate": 1024
}
],
"candidates": [
{
"foundation": 1,
"componentId": 1,
"transport": "udp",
"priority": 2122260223,
"address": "192.168.0.196",
"port": 56143,
"type": "host"
}
],
"ice": {
"ufrag": "af46F",
"pwd": "a34FasdS++jdfofdslkjsd\/SDV"
},
"dtls": {
"hash": "sha-256",
"fingerprint": "F2:AA:0E:C3:22:59:5E:14:95:69:92:3D:13:B4:84:24:2C:C2:A2:C0:3E:FD:34:8E:5E:EA:6F:AF:52:CE:E6:0F"
}
}Author
Sergio Garcia Murillo @ Medooze
License
MIT