sdp offer 流程

1. AmqpClient - New message received

sdp offer 的消息

2023-04-26T21:54:19.790  - DEBUG: AmqpClient - RpcServer New message received {method: 'onTransportSignaling',args: ['b149e44bb10d4e91bd162a8c6806ae7b',{sdp: 'v=0\r\n' +'o=- 7177131362423164715 2 IN IP4 127.0.0.1\r\n' +'s=-\r\n' +'t=0 0\r\n' +'a=group:BUNDLE 0 1\r\n' +'a=msid-semantic: WMS\r\n' +'m=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 102 0 8 106 105 13 110 112 113 126\r\n' +'c=IN IP4 0.0.0.0\r\n' +'a=rtcp:9 IN IP4 0.0.0.0\r\n' +'a=ice-ufrag:h7T4\r\n' +'a=ice-pwd:F0L/DBkHlQzxDgFOclWm8vB7\r\n' +'a=ice-options:trickle\r\n' +'a=fingerprint:sha-256 5D:A4:FF:F1:C1:1B:51:19:CB:26:53:B6:49:2E:97:5F:F1:A4:B7:C7:41:68:AF:19:8D:FA:B1:D6:9D:02:60:4C\r\n' +'a=setup:actpass\r\n' +'a=mid:0\r\n' +'a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\n' +'a=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\n' +'a=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\n' +'a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid\r\n' +'a=extmap:5 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id\r\n' +'a=extmap:6 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id\r\n' +'a=recvonly\r\n' +'a=rtcp-mux\r\n' +'a=rtpmap:111 opus/48000/2\r\n' +'a=rtcp-fb:111 transport-cc\r\n' +'a=fmtp:111 minptime=10;useinbandfec=1\r\n' +'a=rtpmap:103 ISAC/16000\r\n' +'a=rtpmap:104 ISAC/32000\r\n' +'a=rtpmap:9 G722/8000\r\n' +'a=rtpmap:102 ILBC/8000\r\n' +'a=rtpmap:0 PCMU/8000\r\n' +'a=rtpmap:8 PCMA/8000\r\n' +'a=rtpmap:106 CN/32000\r\n' +'a=rtpmap:105 CN/16000\r\n' +'a=rtpmap:13 CN/8000\r\n' +'a=rtpmap:110 telephone-event/48000\r\n' +'a=rtpmap:112 telephone-event/32000\r\n' +'a=rtpmap:113 telephone-event/16000\r\n' +'a=rtpmap:126 telephone-event/8000\r\n' +'m=video 9 UDP/TLS/RTP/SAVPF 123 114 115 116 119\r\n' +'c=IN IP4 0.0.0.0\r\n' +'a=rtcp:9 IN IP4 0.0.0.0\r\n' +'a=ice-ufrag:h7T4\r\n' +'a=ice-pwd:F0L/DBkHlQzxDgFOclWm8vB7\r\n' +'a=ice-options:trickle\r\n' +'a=fingerprint:sha-256 5D:A4:FF:F1:C1:1B:51:19:CB:26:53:B6:49:2E:97:5F:F1:A4:B7:C7:41:68:AF:19:8D:FA:B1:D6:9D:02:60:4C\r\n' +'a=setup:actpass\r\n' +'a=mid:1\r\n' +'a=extmap:14 urn:ietf:params:rtp-hdrext:toffset\r\n' +'a=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\n' +'a=extmap:13 urn:3gpp:video-orientation\r\n' +'a=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\n' +'a=extmap:12 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\n' +'a=extmap:11 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type\r\n' +'a=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing\r\n' +'a=extmap:8 http://tools.ietf.org/html/draft-ietf-avtext-framemarking-07\r\n' +'a=extmap:9 http://www.webrtc.org/experiments/rtp-hdrext/color-space\r\n' +'a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid\r\n' +'a=extmap:5 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id\r\n' +'a=extmap:6 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id\r\n' +'a=recvonly\r\n' +'a=rtcp-mux\r\n' +'a=rtcp-rsize\r\n' +'a=rtpmap:123 AV1/90000\r\n' +'a=rtcp-fb:123 goog-remb\r\n' +'a=rtcp-fb:123 transport-cc\r\n' +'a=rtcp-fb:123 ccm fir\r\n' +'a=rtcp-fb:123 nack\r\n' +'a=rtcp-fb:123 nack pli\r\n' +'a=rtpmap:114 red/90000\r\n' +'a=rtpmap:115 rtx/90000\r\n' +'a=fmtp:115 apt=114\r\n' +'a=rtpmap:116 ulpfec/90000\r\n' +'a=rtpmap:119 rtx/90000\r\n' +'a=fmtp:119 apt=123\r\n',type: 'offer'}],corrID: 39,replyTo: 'amq.gen-WtoELIbC4gJ1GfdYgkvSFA'
}

2. WebrtcNode - onTransportSignaling

dist/webrtc_agent/webrtc/index.js

// connectionId 应该就是operationId
that.onTransportSignaling = function (connectionId, msg, callback) {log.debug('onTransportSignaling, connection id:', connectionId, 'msg:', msg);// 通过 operationId 从mappingTransports 获取 transportId，// 接着通过transportId从peerConnections 获取WrtcConnection// 参考小结 2.1var conn = getWebRTCConnection(connectionId);// WrtcConnection connif (conn) {// 参考小结 2.2conn.onSignalling(msg, connectionId);callback('callback', 'ok');} else {callback('callback', 'error', 'Connection does NOT exist:' + connectionId);}};

2.1 WebrtcNode - getWebRTCConnection——返回WrtcConnection

dist/webrtc_agent/webrtc/index.js

    // 返回的是WrtcConnectionvar getWebRTCConnection = function (operationId) {// 在WebrtcNode-createWebRTCConnection 创建var transportId = mappingTransports.get(operationId);if (peerConnections.has(transportId)) {return peerConnections.get(transportId);}return null;};

2.2 WrtcConnection.onSignalling

dist/webrtc_agent/webrtc/wrtcConnection.js

处理 offer sdp。

  that.onSignalling = function (msg, operationId) {var processSignalling = function () {// 这里type=’offer‘if (msg.type === 'offer') {log.debug('on offer:', msg.sdp);processOffer(msg.sdp);} else if (msg.type === 'candidate') {...} else if (msg.type === 'removed-candidates') {...}};// wrtc 是 Connectionif (wrtc) {processSignalling();} else {// should not reach herelog.error('wrtc is not ready');}};

2.3 ==========WrtcConnection.processOffer

dist/webrtc_agent/webrtc/wrtcConnection.js

这里的 remoteSdp 是null，

 const processOffer = function (sdp) {// 第一进来，remoteSdp 是nullif (!remoteSdp) {// 1. First offerremoteSdp = new SdpInfo(sdp);// Check mid， 获取到mid 数组const mids = remoteSdp.mids();for (const mid of mids) {// 2. 设置finalformatprocessOfferMedia(mid);}// 3. 创建answer sdplocalSdp = remoteSdp.answer();// 4. Setup transportlet opId = null;for (const mid of mids) {if (remoteSdp.getMediaPort(mid) !== 0) {opId = setupTransport(mid);}}if (opId) {on_track({type: 'tracks-complete',operationId: opId});}} else {...}};

  var remoteSdp = null;var localSdp = null;

2.3.1 SdpInfo.SdpInfo

dist/webrtc_agent/webrtc/sdpInfo.js

根据字符串，生成SdpInfo对象。

​

2.3.2 WrtcConnection.processOfferMedia——设置finalformat

WrtcConnection.addTrackOperation, 创建了元素operationMap

设置finalFormat

 const processOfferMedia = function (mid) {...// Determine media format in offerif (remoteSdp.mediaType(mid) === 'audio') {const audioPreference = operationMap.get(mid).formatPreference;// filter audio payloadconst audioFormat = remoteSdp.filterAudioPayload(mid, audioPreference);operationMap.get(mid).finalFormat = audioFormat;} else if (remoteSdp.mediaType(mid) === 'video') {// 这是publish的存储的数据const videoPreference = operationMap.get(mid).formatPreference;// filter video payload    const videoFormat = remoteSdp.filterVideoPayload(mid, videoPreference);// 设置 finalFormatoperationMap.get(mid).finalFormat = videoFormat;}};

operationMap 的元素就是WrtcConnection.addTrackOperation中添加的，这里是给finalFormat赋值

// mid => { operationId, sdpDirection, type, formatPreference, rids, enabled, finalFormat }var operationMap = new Map();

dist/webrtc_agent/webrtc/wrtcConnection.js，在WebrtcNode-subscirbe.md 的addTrackOperation 小节 有详细说明。

SdpInfo.filterVideoPayload

2023-05-31T16:44:11.144  - DEBUG: SdpInfo - filterVideoPayload,
mid=1,
preferenece={"optional":[{"codec":"h264"},
{"codec":"vp8"},{"codec":"vp9"},
{"codec":"av1"},{"codec":"h265"}]}2023-05-31T16:44:11.145  - DEBUG: SdpInfo - filterVideoPayload, 
finalFmt video: {"codec":"av1"}

mediaInfo.rtp

rtp:[{"payload":123,"codec":"AV1","rate":90000},{"payload":114,"codec":"red","rate":90000},{"payload":115,"codec":"rtx","rate":90000},{"payload":116,"codec":"ulpfec","rate":90000},{"payload":119,"codec":"rtx","rate":90000}],

filterVideoPayload(mid, preference) {log.debug("filterVideoPayload,mid="+ mid +",preferenece="+JSON.stringify(preference));// Remove unsupported profilesfilterVP9(this.obj, preference, mid);const finalPrf = filterH264(this.obj, preference, mid);let finalFmt = null;let selectedPayload = -1;// 空const preferred = preference.preferred;const optionals = preference.optional || [];const relatedPayloads = new Set();const allowedFbTypes = ['ccm fir','nack','transport-cc','goog-remb',];const reservedCodecs = ['red', 'ulpfec'];const codecMap = new Map();const payloadOrder = new Map();const mediaInfo = this.media(mid);if (mediaInfo && mediaInfo.type == 'video') {let rtp, fmtp;let payloads;// Keep payload order in m linemediaInfo.payloads.toString().split(' ').forEach((p, index) => {payloadOrder.set(parseInt(p), index);});if (mediaInfo.direction === 'recvonly') {// For subscription// concat(optionals.map((fmt) => fmt.codec.toLowerCase()));optionals.forEach((fmt) => {reservedCodecs.push(fmt.codec.toLowerCase());});}// mediaInfo.rtp 就是上面sdp里的payloadfor (let i = 0; i < mediaInfo.rtp.length; i++) {rtp = mediaInfo.rtp[i];const codec = rtp.codec.toLowerCase();if (reservedCodecs.includes(codec)) {relatedPayloads.add(rtp.payload);}codecMap.set(rtp.payload, codec);// 这个条件不会进入if (preferred && preferred.codec === codec) {selectedPayload = rtp.payload;break;}// 在optional 中找mediaInfo.rtp 的codecif (optionals.findIndex((fmt) => (fmt.codec === codec)) > -1) {if (selectedPayload < 0 ||payloadOrder.get(rtp.payload) < payloadOrder.get(selectedPayload)) {selectedPayload = rtp.payload;}}}// TODO: uncomment following code after register rtx in video receiver// if (!mediaInfo.simulcast) {//   for (i = 0; i < mediaInfo.fmtp.length; i++) {//     fmtp = mediaInfo.fmtp[i];//     if (fmtp.config.indexOf(`apt=${selectedPayload}`) > -1) {//       relatedPayloads.add(fmtp.payload);//     }//   }// }// Remove ulpfec if h264/h265 is selectedconst selectedCodec = codecMap.get(selectedPayload);if (['h264', 'h265'].includes(selectedCodec)) {codecMap.forEach((codec, pt) => {if (codec === 'ulpfec') {relatedPayloads.delete(pt);}});}// Remove red if vp9 SVCif (selectedCodec === 'vp9' && this.getLegacySimulcast(mid)) {codecMap.forEach((codec, pt) => {if (codec === 'red') {relatedPayloads.delete(pt);}});}relatedPayloads.add(selectedPayload);// Remove non-selected video payloadmediaInfo.rtp = mediaInfo.rtp.filter((rtp) => relatedPayloads.has(rtp.payload));if (mediaInfo.fmtp) {mediaInfo.fmtp = mediaInfo.fmtp.filter((fmtp) => relatedPayloads.has(fmtp.payload));}if (mediaInfo.rtcpFb) {mediaInfo.rtcpFb = mediaInfo.rtcpFb.filter((rtcp) => allowedFbTypes.includes(rtcp.type));mediaInfo.rtcpFb = mediaInfo.rtcpFb.filter((rtcp) => relatedPayloads.has(rtcp.payload));}const payloadList = mediaInfo.payloads.toString().split(' ');if (selectedPayload !== -1) {payloadList.unshift(selectedPayload.toString());}mediaInfo.payloads = payloadList.filter((p) => relatedPayloads.has(parseInt(p))).filter((v, index, self) => self.indexOf(v) === index).join(' ');}if (selectedPayload !== -1) {finalFmt = { codec: codecMap.get(selectedPayload) };if (finalFmt.codec === 'h264' && finalPrf) {finalFmt.profile = finalPrf;}}log.debug('filterVideoPayload, finalFmt video:', JSON.stringify(finalFmt));return finalFmt;}

2.3.3 SdpInfo.answer——localSdp

通过offer到sdp，进行对应的修改，作为answer的sdp。赋值给localSdp中，在WrtcConnection.setupTransport用到。

 answer() {const answer = new SdpInfo(this.toString());answer.obj.origin = {username: '-',sessionId: '0',sessionVersion: 0,netType: 'IN',ipVer: 4,address: '127.0.0.1'};answer.obj.media.forEach(mediaInfo => {mediaInfo.port = 1;mediaInfo.rtcp = {port: 1,netType: 'IN',ipVer: 4,address: '0.0.0.0'};if (mediaInfo.setup === 'active') {mediaInfo.setup = 'passive';} else {mediaInfo.setup = 'active';}delete mediaInfo.iceOptions;  delete mediaInfo.rtcpRsize;if (mediaInfo.direction === 'recvonly') {mediaInfo.direction = 'sendonly';} else if (mediaInfo.direction === 'sendonly') {delete mediaInfo.msid;delete mediaInfo.ssrcGroups;delete mediaInfo.ssrcs;mediaInfo.direction = 'recvonly';}if (mediaInfo.ext && Array.isArray(mediaInfo.ext)) {const extMappings = ['urn:ietf:params:rtp-hdrext:ssrc-audio-level',// 'http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01','urn:ietf:params:rtp-hdrext:sdes:mid','urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id','urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id','urn:ietf:params:rtp-hdrext:toffset','http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time',// 'urn:3gpp:video-orientation',// 'http://www.webrtc.org/experiments/rtp-hdrext/playout-delay',];if (mediaInfo.type === 'video') {extMappings.push('http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01');}mediaInfo.ext = mediaInfo.ext.filter((e) => {return extMappings.includes(e.uri);});}if (mediaInfo.rids && Array.isArray(mediaInfo.rids)) {// Reverse rids directionmediaInfo.rids.forEach(r => {r.direction = (r.direction === 'send') ? 'recv' : 'send';});}if (mediaInfo.simulcast) {// Reverse simulcast directionif (mediaInfo.simulcast.dir1 === 'send') {mediaInfo.simulcast.dir1 = 'recv';} else {mediaInfo.simulcast.dir1 = 'send';}}});return answer;}

SdpInfo.getMediaPort

m=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 102 0 8 106 105 13 110 112 113 126m=video 9 UDP/TLS/RTP/SAVPF 123 114 115 116 119

9 就是port

SdpInfo.mediaType

m=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 102 0 8 106 105 13 110 112 113 126m=video 9 UDP/TLS/RTP/SAVPF 123 114 115 116 119

auido/video， 就是mediaType

operationMap——存放的是track相关的内容

dist/webrtc_agent/webrtc/wrtcConnection.js

在WebrtcNode-subscribe.md 的addTrackOperation 小节 有详细说明

  // mid => { operationId, sdpDirection, type, formatPreference, rids, enabled, finalFormat }var operationMap = new Map();

2.3.4 WrtcConnection.setupTransport——创建WrtcStream

dist/webrtc_agent/webrtc/wrtcConnection.js

小节 3

2.3.5 on_track——这是创建WrtcConnection 传入的callback,tracks-complete

在WebrtcNode-subscribe.md 的 3.WebrtcNode - createWebRTCConnection——返回WrtcConnection 中传入了

function onTrack(trackInfo) {handleTrackInfo(transportId, trackInfo, controller);}

调用的代码

        on_track({type: 'tracks-complete',operationId: opId});

详细的看3.3， 3.4 小节

3. WrtcConnection.setupTransport——创建WrtcStream

主要是创建MediaStream。

dist/webrtc_agent/webrtc/wrtcConnection.js

2023-04-26T21:54:19.800  - DEBUG: WrtcConnection - Add ssrc 1735005623 
to video in SDP for b149e44bb10d4e91bd162a8c6806ae7b2023-04-26T21:54:19.800  - DEBUG: SdpInfo - Set SSRC: 1 [
{"id":1735005623,"attribute":"cname","value":"o/i14u9pJrxRKAsu"},
{"id":1735005623,"attribute":"msid","value":"guSQ9WN0ZG v0"},
{"id":1735005623,"attribute":"mslabel","value":"guSQ9WN0ZG"},
{"id":1735005623,"attribute":"label","value":"guSQ9WN0ZGv0"}]
2023-04-26 21:54:19,802  - DEBUG: WebRtcConnection - 
id: b149e44bb10d4e91bd162a8c6806ae7b,  message: setting remote SDP
2023-04-26 21:54:19,802  - DEBUG: WebRtcConnection - 
id: b149e44bb10d4e91bd162a8c6806ae7b,  message: processing remote SDP

const setupTransport = function (mid) {let rids = remoteSdp.rids(mid);const opSettings = operationMap.get(mid);// recvonly, 是outconst direction = (opSettings.sdpDirection === 'sendonly') ? 'in' : 'out';const simSsrcs = remoteSdp.getLegacySimulcast(mid);const trackSettings = remoteSdp.getMediaSettings(mid);const mediaType = remoteSdp.mediaType(mid);trackSettings.owner = owner; // 用户idtrackSettings.enableBWE = that.enableBWE;if (opSettings.finalFormat) {trackSettings[mediaType].format = opSettings.finalFormat;if (opSettings.finalFormat.codec === 'vp9' && simSsrcs) {// Legacy simulcast for VP9 SVCrids = null;trackSettings['video'].scalabilityMode = opSettings.scalabilityMode;}}if (rids) {...} else {// 走这里的代码// No simulcastif (!trackMap.has(mid)) {// 1. Connection wrtctrackMap.set(mid, new WrtcStream(mid, wrtc, direction, trackSettings));// Set ssrc in local sdp for out direction// direct 是outif (direction === 'out') {// mtype = ‘video’const mtype = localSdp.mediaType(mid);// 2. 在WrtcStream 创建的时候，创建了videoFramePacketizer// 从WrtcStream 获取ssrcconst ssrc = trackMap.get(mid).ssrc(mtype);if (ssrc) {log.debug(`Add ssrc ${ssrc} to ${mtype} in SDP for ${wrtcId}`);const opId = opSettings.operationId;let msid = msidMap.get(opId);// 3. setSsrcsif (msid) {localSdp.setSsrcs(mid, [ssrc], msid);} else {msid = localSdp.setSsrcs(mid, [ssrc]);msidMap.set(opId, msid);}}}// 4. Connection wrtc// remoteSdp 是在processOffer 创建的对象， client端发过来的sdpwrtc.setRemoteSdp(remoteSdp.singleMediaSdp(mid).toString(), mid);// 5. Notify new track， 详细见小节 3.5， 3.6// on_track， wrtcConnection 就是在创建的时候，传入的参数on_track({type: 'track-added',track: trackMap.get(mid),// WrtcStreamoperationId: opSettings.operationId,mid: mid});} else {log.warn(`Conflict trackId ${mid} for ${wrtcId}`);}}return opSettings.operationId;};

SdpInfo.rids

trackMap 属性——存放了WrtcStream

  // composedId => WrtcStreamvar trackMap = new Map();

composeId

  const composeId = function (mid, rid) {return mid + ':' + rid;};

3.1 new WrtcStream

小节 4
创建了MediaStream

见文章 WebrtcNode-subscribe-sdpOffer(2).md

>>>>>>>>>>>>不同于publish的流程>>>>>>>>>>

3.2 WrtcStream.ssrc

dist/webrtc_agent/webrtc/wrtcConnection.js

  ssrc(track) {if (track === 'audio' && this.audioFramePacketizer) {return this.audioFramePacketizer.ssrc();}if (track === 'video' && this.videoFramePacketizer) {return this.videoFramePacketizer.ssrc();}return null;}

3.2.1 addon.VideoFramePacketizer::getSsrc

source/agent/webrtc/rtcFrame/VideoFramePacketizerWrapper.cc

void VideoFramePacketizer::getSsrc(const v8::FunctionCallbackInfo<v8::Value>& args) {Isolate* isolate = Isolate::GetCurrent();HandleScope scope(isolate);VideoFramePacketizer* obj = ObjectWrap::Unwrap<VideoFramePacketizer>(args.Holder());owt_base::VideoFramePacketizer* me = obj->me;uint32_t ssrc = me->getSsrc();args.GetReturnValue().Set(Number::New(isolate, ssrc));
}

3.2.2 owt_base::VideoFramePacketizer

    uint32_t m_ssrc;uint32_t getSsrc() { return m_ssrc; }

bool VideoFramePacketizer::init(VideoFramePacketizer::Config& config)
{if (!m_videoSend) {// Create Send Video Stream...m_videoSend = m_rtcAdapter->createVideoSender(sendConfig);m_ssrc = m_videoSend->ssrc();return true;}return false;
}

3.3 ？？？SdpInfo.setSsrcs

这里设置sscrs是什么作用

// ssrcs = [1735005623]
setSsrcs(mid, ssrcs, msid) {log.debug('setSsrcs,mid='+mid+",ssrcs="+ssrcs+",msid="+msid);const media = this.media(mid);if (!media) {return null;}if (!msid) {// Generate msidconst alphanum = '0123456789' +'ABCDEFGHIJKLMNOPQRSTUVWXYZ' +'abcdefghijklmnopqrstuvwxyz';const msidLength = 10;msid = '';for (let i = 0; i < msidLength; i++) {msid += alphanum[Math.floor(Math.random() * alphanum.length)];}}const mtype = (media.type === 'audio') ? 'a' : 'v';// Only support one ssrc nowconst ssrc = ssrcs[0];media.ssrcs = [{id: ssrc, attribute: 'cname', value: 'o/i14u9pJrxRKAsu'},{id: ssrc, attribute: 'msid', value: `${msid} ${mtype}0`},{id: ssrc, attribute: 'mslabel', value: msid},{id: ssrc, attribute: 'label', value: `${msid}${mtype}0`},];log.debug('Set SSRC:', mid, msid, JSON.stringify(media.ssrcs));return msid;}

<<<<<<<<<<<<<<<<<不同于publish的流程<<<<<<<<<<

3.4 Connection.setRemoteSdp

// streamId = mid
setRemoteSdp(sdp, streamId) {// webRtcConnection wrtcthis.wrtc.setRemoteSdp(sdp, streamId || this.id);}

3.4.1 NAN_METHOD(WebRtcConnection::setRemoteSdp)

source/agent/webrtc/rtcConn/WebRtcConnection.cc

NAN_METHOD(WebRtcConnection::setRemoteSdp) {WebRtcConnection* obj = Nan::ObjectWrap::Unwrap<WebRtcConnection>(info.Holder());std::shared_ptr<erizo::WebRtcConnection> me = obj->me;if (!me) {return;}std::string sdp = getString(info[0]);std::string stream_id = getString(info[1]);bool r = me->setRemoteSdp(sdp, stream_id);info.GetReturnValue().Set(Nan::New(r));
}

3.4.2 erizo::WebRtcConnection::setRemoteSdp

source/agent/webrtc/rtcConn/erizo/src/erizo/WebRtcConnection.cpp

2023-04-26 21:54:19,802  - DEBUG: WebRtcConnection - 
id: b149e44bb10d4e91bd162a8c6806ae7b, message: setting remote SDP

bool WebRtcConnection::setRemoteSdpInfo(std::shared_ptr<SdpInfo> sdp, std::string stream_id) {asyncTask([sdp, stream_id] (std::shared_ptr<WebRtcConnection> connection) {ELOG_DEBUG("%s message: setting remote SDPInfo", connection->toLog());if (!connection->sending_) {return;}connection->remote_sdp_ = sdp;// mid connection->processRemoteSdp(stream_id);});return true;
}

??? erizo::WebRtcConnection::processRemoteSdp

source/agent/webrtc/rtcConn/erizo/src/erizo/WebRtcConnection.cpp

2023-04-26 21:54:19,802  - DEBUG: WebRtcConnection - id: b149e44bb10d4e91bd162a8c6806ae7b,  message: processing remote SDP

见后文owt-server/WebRTCEvent.md

SdpInfo.singleMediaSdp

dist-debug/webrtc_agent/webrtc/sdpInfo.js

  singleMediaSdp(mid) {const sdp = new SdpInfo(this.toString());sdp.obj.media = sdp.obj.media.filter(m => m.mid.toString() === mid);sdp.setBundleMids([mid]);return sdp;}

3.5 on__track——track add

dist/webrtc_agent/webrtc/wrtcConnection.js

通知到WebrtcNode（/dist/webrtc_agent/webrtc/index.js）的createWebRTCConnection 中注册的callback, 回调一个对象，

        // Notify new trackon_track({type: 'track-added',track: trackMap.get(mid), // WrtcStreamoperationId: opSettings.operationId,mid: mid})

3.6 ======WebrtcNode.handleTrackInfo

dist/webrtc_agent/webrtc/index.js

// 这里传入onTrack， 就是on_track，就是 callback
var connection = new WrtcConnection({connectionId: transportId,threadPool: threadPool,ioThreadPool: ioThreadPool,network_interfaces: global.config.webrtc.network_interfaces,owner,}, function onTransportStatus(status) {notifyTransportStatus(controller, transportId, status);}, function onTrack(trackInfo) {/* trackInfo 就是 {type: 'track-added',track: trackMap.get(mid), // WrtcStreamoperationId: opSettings.operationId,mid: mid}*/handleTrackInfo(transportId, trackInfo, controller);});

// trackInfo 就是on__track 回调回来
var handleTrackInfo = function (transportId, trackInfo, controller) {var publicTrackId;var updateInfo;if (trackInfo.type === 'track-added') {// Generate public track IDconst track = trackInfo.track; // WrtcStreampublicTrackId = transportId + '-' + track.id;if (mediaTracks.has(publicTrackId)) {log.error('Conflict public track id:', publicTrackId, transportId, track.id);return;}mediaTracks.set(publicTrackId, track);mappingPublicId.get(transportId).set(track.id, publicTrackId);if (track.direction === 'in') {const trackSource = track.sender();router.addLocalSource(publicTrackId, 'webrtc', trackSource).catch(e => log.warn('Unexpected error during track add:', e));} else {// 走这里router.addLocalDestination(publicTrackId, 'webrtc', track).catch(e => log.warn('Unexpected error during track add:', e));}// Bind media-update handlertrack.on('media-update', (jsonUpdate) => {log.debug('notifyMediaUpdate:', publicTrackId, jsonUpdate);notifyMediaUpdate(controller, publicTrackId, track.direction, JSON.parse(jsonUpdate));});// Notify controllerconst mediaType = track.format('audio') ? 'audio' : 'video';updateInfo = {type: 'track-added',trackId: publicTrackId,mediaType: track.format('audio') ? 'audio' : 'video',mediaFormat: track.format(mediaType),direction: track.direction,operationId: trackInfo.operationId,mid: trackInfo.mid,rid: trackInfo.rid,active: true,};log.debug('notifyTrackUpdate', controller, publicTrackId, updateInfo);notifyTrackUpdate(controller, transportId, updateInfo);} else if (trackInfo.type === 'track-removed') {publicTrackId = mappingPublicId.get(transportId).get(trackInfo.trackId);if (!mediaTracks.has(publicTrackId)) {log.error('Non-exist public track id:', publicTrackId, transportId, trackInfo.trackId);return;}log.debug('track removed:', publicTrackId);router.removeConnection(publicTrackId).then(ok => {mediaTracks.get(publicTrackId).close();mediaTracks.delete(publicTrackId);mappingPublicId.get(transportId).delete(trackInfo.trackId);}).catch(e => log.warn('Unexpected error during track remove:', e));// Notify controllerupdateInfo = {type: 'track-removed',trackId: publicTrackId,};notifyTrackUpdate(controller, transportId, updateInfo);} else if (trackInfo.type === 'tracks-complete') {updateInfo = {type: 'tracks-complete',operationId: trackInfo.operationId};notifyTrackUpdate(controller, transportId, updateInfo);}};

详细说明见后文 WebrtcNode-subscribe-sdpOffer(3).md的2. WebrtcNode.handleTrackInfo 。

流程图