WebRTC Signaling Interaction Format

ZLMediaKitAbout 5 min

Introduction

zlmediakit has added support for the whip/whep standard in the WebRTC signaling format. The test url are as follows:

Push stream：https://zlmediakit.com/index/api/whip?app=live&stream=test

Pull stream：https://zlmediakit.com/index/api/whep?app=live&stream=test

The subsequent sections of this article will cover the private signaling format.

1. Basic Format of WebRTC SDP Exchange Request

Request URL: /index/api/webrtc?app=live&stream=test&type=[push/play/echo]
Request Method: HTTP POST
Request Body: WebRTC offer SDP

Response Body:

{
  "code": 0,
  "id": "zlm_1",
  "sdp": "v=0\r\no=mozilla...THIS_IS_SDPARTA-99.0 6880954646154322397 0 IN IP4 172.18.190.185\r\ns=-\r\nt=0 0\r\na=group:BUNDLE 0 1\r\na=msid-semantic: WMS *\r\na=ice-lite\r\nm=audio 8000 UDP/TLS/RTP/SAVPF 0\r\nc=IN IP4 172.18.190.185\r\na=rtcp:8000 IN IP4 172.18.190.185\r\na=ice-ufrag:rBK+uR9AAAA=_2\r\na=ice-pwd:H4rtFC1xhef0ynU2lk8z22ha\r\na=fingerprint:sha-256 6E:EF:E7:75:56:2A:66:DF:6C:9D:72:B6:A5:21:35:73:19:66:D8:00:F4:BC:36:59:61:1B:5D:35:13:99:14:AE\r\na=setup:passive\r\na=mid:0\r\na=ice-lite\r\na=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\na=extmap:2/sendonly urn:ietf:params:rtp-hdrext:csrc-audio-level\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:0 PCMU/8000/1\r\na=candidate:udpcandidate 1 udp 120 172.18.190.185 8000 typ host\r\nm=video 8000 UDP/TLS/RTP/SAVPF 126 127\r\nc=IN IP4 172.18.190.185\r\na=rtcp:8000 IN IP4 172.18.190.185\r\na=ice-ufrag:rBK+uR9AAAA=_2\r\na=ice-pwd:H4rtFC1xhef0ynU2lk8z22ha\r\na=fingerprint:sha-256 6E:EF:E7:75:56:2A:66:DF:6C:9D:72:B6:A5:21:35:73:19:66:D8:00:F4:BC:36:59:61:1B:5D:35:13:99:14:AE\r\na=setup:passive\r\na=mid:1\r\na=ice-lite\r\na=extmap:4 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:5 urn:ietf:params:rtp-hdrext:toffset\r\na=extmap:6/sendonly http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\na=extmap:7 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:126 H264/90000\r\na=rtcp-fb:126 ccm fir\r\na=rtcp-fb:126 goog-remb\r\na=rtcp-fb:126 nack\r\na=rtcp-fb:126 nack pli\r\na=rtcp-fb:126 transport-cc\r\na=fmtp:126 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f;x-google-max-bitrate=8000;x-google-min-bitrate=4000;x-google-start-bitrate=6000\r\na=rtpmap:127 rtx/90000\r\na=fmtp:127 apt=126\r\na=candidate:udpcandidate 1 udp 120 172.18.190.185 8000 typ host\r\n",
  "type": "answer"
}

2. Supported Type Types

push: WebRTC streaming
play: WebRTC playback
echo: WebRTC mirroring and echo (only for WebRTC bidirectional testing)
Users can develop and register additional type plugins for customization.

3. Example

Request：

POST /index/api/webrtc?app=live&stream=test&type=push HTTP/1.1
Host: 127.0.0.1:8080
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/111.0
Accept: application/json, text/plain, */*
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate, br
Content-Type: text/plain;charset=utf-8
Content-Length: 2654
Origin: http://127.0.0.1:8080
Connection: keep-alive
Referer: http://127.0.0.1:8080/webrtc/
Cookie: ZL_COOKIE=45bcd71af9fbfa8fe576d1ef3f42ef69
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-origin

v=0
o=mozilla...THIS_IS_SDPARTA-99.0 6880954646154322397 0 IN IP4 0.0.0.0
s=-
t=0 0
a=fingerprint:sha-256 10:09:E1:DB:B6:2D:58:ED:B3:7A:7A:B7:77:34:64:06:65:E7:5F:F2:CB:B5:BA:1A:C5:7C:A6:F5:8C:29:45:E0
a=group:BUNDLE 0 1
a=ice-options:trickle
a=msid-semantic:WMS *
m=audio 9 UDP/TLS/RTP/SAVPF 109 9 0 8 101
c=IN IP4 0.0.0.0
a=sendrecv
a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level
a=extmap:2/recvonly urn:ietf:params:rtp-hdrext:csrc-audio-level
a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:mid
a=fmtp:109 maxplaybackrate=48000;stereo=1;useinbandfec=1
a=fmtp:101 0-15
a=ice-pwd:e4efb3b86c1b7e1cb8fd949db7796641
a=ice-ufrag:24ab201c
a=mid:0
a=msid:- {2320d86d-4e2f-4c3f-a378-b9e701dceeae}
a=rtcp-mux
a=rtpmap:109 opus/48000/2
a=rtpmap:9 G722/8000/1
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000/1
a=setup:actpass
a=ssrc:1347702353 cname:{e94c5049-fb95-4bd6-b2d1-221cd51b713f}
m=video 9 UDP/TLS/RTP/SAVPF 120 124 121 125 126 127 97 98
c=IN IP4 0.0.0.0
a=sendrecv
a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:mid
a=extmap:4 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=extmap:5 urn:ietf:params:rtp-hdrext:toffset
a=extmap:6/recvonly http://www.webrtc.org/experiments/rtp-hdrext/playout-delay
a=extmap:7 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01
a=fmtp:126 profile-level-id=42e01f;level-asymmetry-allowed=1;packetization-mode=1
a=fmtp:97 profile-level-id=42e01f;level-asymmetry-allowed=1
a=fmtp:120 max-fs=12288;max-fr=60
a=fmtp:124 apt=120
a=fmtp:121 max-fs=12288;max-fr=60
a=fmtp:125 apt=121
a=fmtp:127 apt=126
a=fmtp:98 apt=97
a=ice-pwd:e4efb3b86c1b7e1cb8fd949db7796641
a=ice-ufrag:24ab201c
a=mid:1
a=msid:- {270d6bf9-cf47-4e3f-9bb5-e9bf7143ea4a}
a=rtcp-fb:120 nack
a=rtcp-fb:120 nack pli
a=rtcp-fb:120 ccm fir
a=rtcp-fb:120 goog-remb
a=rtcp-fb:120 transport-cc
a=rtcp-fb:121 nack
a=rtcp-fb:121 nack pli
a=rtcp-fb:121 ccm fir
a=rtcp-fb:121 goog-remb
a=rtcp-fb:121 transport-cc
a=rtcp-fb:126 nack
a=rtcp-fb:126 nack pli
a=rtcp-fb:126 ccm fir
a=rtcp-fb:126 goog-remb
a=rtcp-fb:126 transport-cc
a=rtcp-fb:97 nack
a=rtcp-fb:97 nack pli
a=rtcp-fb:97 ccm fir
a=rtcp-fb:97 goog-remb
a=rtcp-fb:97 transport-cc
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:120 VP8/90000
a=rtpmap:124 rtx/90000
a=rtpmap:121 VP9/90000
a=rtpmap:125 rtx/90000
a=rtpmap:126 H264/90000
a=rtpmap:127 rtx/90000
a=rtpmap:97 H264/90000
a=rtpmap:98 rtx/90000
a=setup:actpass
a=ssrc:3676200744 cname:{e94c5049-fb95-4bd6-b2d1-221cd51b713f}
a=ssrc:3937745592 cname:{e94c5049-fb95-4bd6-b2d1-221cd51b713f}
a=ssrc-group:FID 3676200744 3937745592

Response：

HTTP/1.1 200 OK
Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: *
Connection: keep-alive
Content-Length: 1923
Content-Type: application/json
Date: Wed, Mar 29 2023 12:43:08 GMT
Keep-Alive: timeout=30, max=100
Server: ZLMediaKit(git hash:500d2c6a/2023-03-14T17:33:46+08:00,branch:master,build time:2023-03-15T15:03:55)

{
   "code" : 0,
   "id" : "zlm_1",
   "sdp" : "v=0\r\no=mozilla...THIS_IS_SDPARTA-99.0 6880954646154322397 0 IN IP4 172.18.190.185\r\ns=-\r\nt=0 0\r\na=group:BUNDLE 0 1\r\na=msid-semantic: WMS *\r\na=ice-lite\r\nm=audio 8000 UDP/TLS/RTP/SAVPF 0\r\nc=IN IP4 172.18.190.185\r\na=rtcp:8000 IN IP4 172.18.190.185\r\na=ice-ufrag:rBK+uR9AAAA=_2\r\na=ice-pwd:H4rtFC1xhef0ynU2lk8z22ha\r\na=fingerprint:sha-256 6E:EF:E7:75:56:2A:66:DF:6C:9D:72:B6:A5:21:35:73:19:66:D8:00:F4:BC:36:59:61:1B:5D:35:13:99:14:AE\r\na=setup:passive\r\na=mid:0\r\na=ice-lite\r\na=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\na=extmap:2/sendonly urn:ietf:params:rtp-hdrext:csrc-audio-level\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:0 PCMU/8000/1\r\na=candidate:udpcandidate 1 udp 120 172.18.190.185 8000 typ host\r\nm=video 8000 UDP/TLS/RTP/SAVPF 126 127\r\nc=IN IP4 172.18.190.185\r\na=rtcp:8000 IN IP4 172.18.190.185\r\na=ice-ufrag:rBK+uR9AAAA=_2\r\na=ice-pwd:H4rtFC1xhef0ynU2lk8z22ha\r\na=fingerprint:sha-256 6E:EF:E7:75:56:2A:66:DF:6C:9D:72:B6:A5:21:35:73:19:66:D8:00:F4:BC:36:59:61:1B:5D:35:13:99:14:AE\r\na=setup:passive\r\na=mid:1\r\na=ice-lite\r\na=extmap:4 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:5 urn:ietf:params:rtp-hdrext:toffset\r\na=extmap:6/sendonly http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\na=extmap:7 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:126 H264/90000\r\na=rtcp-fb:126 ccm fir\r\na=rtcp-fb:126 goog-remb\r\na=rtcp-fb:126 nack\r\na=rtcp-fb:126 nack pli\r\na=rtcp-fb:126 transport-cc\r\na=fmtp:126 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f;x-google-max-bitrate=8000;x-google-min-bitrate=4000;x-google-start-bitrate=6000\r\na=rtpmap:127 rtx/90000\r\na=fmtp:127 apt=126\r\na=candidate:udpcandidate 1 udp 120 172.18.190.185 8000 typ host\r\n",
   "type" : "answer"
}

WebRTC Signaling Interaction Format

# Introduction

# 1. Basic Format of WebRTC SDP Exchange Request

# 2. Supported Type Types

# 3. Example

Introduction

1. Basic Format of WebRTC SDP Exchange Request

2. Supported Type Types

3. Example