视频会议

node_modules/sdp/.eslintrc

@@ -0,0 +1,61 @@
+{
+  "rules": {
+    "array-bracket-spacing": 2,
+    "block-spacing": [2, "never"],
+    "brace-style": [2, "1tbs", {"allowSingleLine": false}],
+    "camelcase": [2, {"properties": "always"}],
+    "curly": 2,
+    "default-case": 2,
+    "dot-notation": 2,
+    "eqeqeq": 2,
+    "indent": [
+        2,
+        2,
+        {"SwitchCase": 1}
+    ],
+    "key-spacing": [2, {"beforeColon": false, "afterColon": true}],
+    "max-len": [2, 80, 2, {"ignoreUrls": true}],
+    "new-cap": [2, {"newIsCapExceptions": [
+        "webkitRTCPeerConnection",
+        "mozRTCPeerConnection"
+    ]}],
+    "no-console": 0,
+    "no-else-return": 2,
+    "no-eval": 2,
+    "no-multi-spaces": 2,
+    "no-multiple-empty-lines": [2, {"max": 2}],
+    "no-shadow": 2,
+    "no-trailing-spaces": 2,
+    "no-unused-expressions": 2,
+    "no-unused-vars": [2, {"args": "none"}],
+    "object-curly-spacing": [2, "never"],
+    "padded-blocks": [2, "never"],
+    "quotes": [
+        2,
+        "single"
+    ],
+    "semi": [
+        2,
+        "always"
+    ],
+    "keyword-spacing": 2,
+    "space-before-blocks": 2,
+    "space-before-function-paren": [2, "never"],
+    "space-unary-ops": 2,
+    "space-infix-ops": 2,
+    "spaced-comment": 2,
+    "valid-typeof": 2
+  },
+  "env": {
+      "es6": true,
+      "browser": true,
+      "node": true
+  },
+  "extends": ["eslint:recommended"],
+  "globals": {
+    "module": true,
+    "require": true,
+    "process": true,
+    "Promise": true,
+  }
+}

node_modules/sdp/.github/workflows/npm-test.yml

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+name: npm-test
+
+on: [pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions/setup-node@v3
+    - run: npm install
+    - run: npm test
+    - run: npm run coverage
+    - uses: codecov/codecov-action@v1
+      with:
+        file: ./coverage.lcov

node_modules/sdp/.nyc_output/processinfo/a9b935d8-5f14-4c64-b895-6b0ece2e9d7c.json

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+{"uuid":"a9b935d8-5f14-4c64-b895-6b0ece2e9d7c","parent":null,"pid":5750,"argv":["/usr/bin/node","/media/fippo/houseparty/webrtc/sdp/node_modules/.bin/mocha","test/sdp.js"],"execArgv":[],"cwd":"/media/fippo/houseparty/webrtc/sdp","time":1673267457493,"ppid":5743,"root":"9110d26c-7a83-40c7-a41d-9670d698bc02","coverageFilename":"/media/fippo/houseparty/webrtc/sdp/.nyc_output/a9b935d8-5f14-4c64-b895-6b0ece2e9d7c.json","files":["/media/fippo/houseparty/webrtc/sdp/sdp.js"]}

node_modules/sdp/.nyc_output/processinfo/index.json

@@ -0,0 +1 @@
+{"processes":{"a9b935d8-5f14-4c64-b895-6b0ece2e9d7c":{"parent":null,"children":[]}},"files":{"/media/fippo/houseparty/webrtc/sdp/sdp.js":["a9b935d8-5f14-4c64-b895-6b0ece2e9d7c"]},"externalIds":{}}

node_modules/sdp/LICENSE

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+Copyright (c) 2017 Philipp Hancke
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

node_modules/sdp/README.md

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+# SDP parsing and utlities
+originally for generating SDP from ORTC and vice versa -- see https://github.com/fippo/adapter/tree/shim-ortc
+
+But it turned out to be useful for manipulating SDP outside the context of Microsofts Edge browser.

node_modules/sdp/dist/sdp.js

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+/* eslint-env node */
+'use strict';
+
+// SDP helpers.
+
+var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
+
+var SDPUtils = {};
+
+// Generate an alphanumeric identifier for cname or mids.
+// TODO: use UUIDs instead? https://gist.github.com/jed/982883
+SDPUtils.generateIdentifier = function () {
+  return Math.random().toString(36).substring(2, 12);
+};
+
+// The RTCP CNAME used by all peerconnections from the same JS.
+SDPUtils.localCName = SDPUtils.generateIdentifier();
+
+// Splits SDP into lines, dealing with both CRLF and LF.
+SDPUtils.splitLines = function (blob) {
+  return blob.trim().split('\n').map(function (line) {
+    return line.trim();
+  });
+};
+// Splits SDP into sessionpart and mediasections. Ensures CRLF.
+SDPUtils.splitSections = function (blob) {
+  var parts = blob.split('\nm=');
+  return parts.map(function (part, index) {
+    return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
+  });
+};
+
+// Returns the session description.
+SDPUtils.getDescription = function (blob) {
+  var sections = SDPUtils.splitSections(blob);
+  return sections && sections[0];
+};
+
+// Returns the individual media sections.
+SDPUtils.getMediaSections = function (blob) {
+  var sections = SDPUtils.splitSections(blob);
+  sections.shift();
+  return sections;
+};
+
+// Returns lines that start with a certain prefix.
+SDPUtils.matchPrefix = function (blob, prefix) {
+  return SDPUtils.splitLines(blob).filter(function (line) {
+    return line.indexOf(prefix) === 0;
+  });
+};
+
+// Parses an ICE candidate line. Sample input:
+// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
+// rport 55996"
+// Input can be prefixed with a=.
+SDPUtils.parseCandidate = function (line) {
+  var parts = void 0;
+  // Parse both variants.
+  if (line.indexOf('a=candidate:') === 0) {
+    parts = line.substring(12).split(' ');
+  } else {
+    parts = line.substring(10).split(' ');
+  }
+
+  var candidate = {
+    foundation: parts[0],
+    component: { 1: 'rtp', 2: 'rtcp' }[parts[1]] || parts[1],
+    protocol: parts[2].toLowerCase(),
+    priority: parseInt(parts[3], 10),
+    ip: parts[4],
+    address: parts[4], // address is an alias for ip.
+    port: parseInt(parts[5], 10),
+    // skip parts[6] == 'typ'
+    type: parts[7]
+  };
+
+  for (var i = 8; i < parts.length; i += 2) {
+    switch (parts[i]) {
+      case 'raddr':
+        candidate.relatedAddress = parts[i + 1];
+        break;
+      case 'rport':
+        candidate.relatedPort = parseInt(parts[i + 1], 10);
+        break;
+      case 'tcptype':
+        candidate.tcpType = parts[i + 1];
+        break;
+      case 'ufrag':
+        candidate.ufrag = parts[i + 1]; // for backward compatibility.
+        candidate.usernameFragment = parts[i + 1];
+        break;
+      default:
+        // extension handling, in particular ufrag. Don't overwrite.
+        if (candidate[parts[i]] === undefined) {
+          candidate[parts[i]] = parts[i + 1];
+        }
+        break;
+    }
+  }
+  return candidate;
+};
+
+// Translates a candidate object into SDP candidate attribute.
+// This does not include the a= prefix!
+SDPUtils.writeCandidate = function (candidate) {
+  var sdp = [];
+  sdp.push(candidate.foundation);
+
+  var component = candidate.component;
+  if (component === 'rtp') {
+    sdp.push(1);
+  } else if (component === 'rtcp') {
+    sdp.push(2);
+  } else {
+    sdp.push(component);
+  }
+  sdp.push(candidate.protocol.toUpperCase());
+  sdp.push(candidate.priority);
+  sdp.push(candidate.address || candidate.ip);
+  sdp.push(candidate.port);
+
+  var type = candidate.type;
+  sdp.push('typ');
+  sdp.push(type);
+  if (type !== 'host' && candidate.relatedAddress && candidate.relatedPort) {
+    sdp.push('raddr');
+    sdp.push(candidate.relatedAddress);
+    sdp.push('rport');
+    sdp.push(candidate.relatedPort);
+  }
+  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
+    sdp.push('tcptype');
+    sdp.push(candidate.tcpType);
+  }
+  if (candidate.usernameFragment || candidate.ufrag) {
+    sdp.push('ufrag');
+    sdp.push(candidate.usernameFragment || candidate.ufrag);
+  }
+  return 'candidate:' + sdp.join(' ');
+};
+
+// Parses an ice-options line, returns an array of option tags.
+// Sample input:
+// a=ice-options:foo bar
+SDPUtils.parseIceOptions = function (line) {
+  return line.substring(14).split(' ');
+};
+
+// Parses a rtpmap line, returns RTCRtpCoddecParameters. Sample input:
+// a=rtpmap:111 opus/48000/2
+SDPUtils.parseRtpMap = function (line) {
+  var parts = line.substring(9).split(' ');
+  var parsed = {
+    payloadType: parseInt(parts.shift(), 10) // was: id
+  };
+
+  parts = parts[0].split('/');
+
+  parsed.name = parts[0];
+  parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
+  parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
+  // legacy alias, got renamed back to channels in ORTC.
+  parsed.numChannels = parsed.channels;
+  return parsed;
+};
+
+// Generates a rtpmap line from RTCRtpCodecCapability or
+// RTCRtpCodecParameters.
+SDPUtils.writeRtpMap = function (codec) {
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  var channels = codec.channels || codec.numChannels || 1;
+  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate + (channels !== 1 ? '/' + channels : '') + '\r\n';
+};
+
+// Parses a extmap line (headerextension from RFC 5285). Sample input:
+// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
+// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
+SDPUtils.parseExtmap = function (line) {
+  var parts = line.substring(9).split(' ');
+  return {
+    id: parseInt(parts[0], 10),
+    direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
+    uri: parts[1],
+    attributes: parts.slice(2).join(' ')
+  };
+};
+
+// Generates an extmap line from RTCRtpHeaderExtensionParameters or
+// RTCRtpHeaderExtension.
+SDPUtils.writeExtmap = function (headerExtension) {
+  return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) + (headerExtension.direction && headerExtension.direction !== 'sendrecv' ? '/' + headerExtension.direction : '') + ' ' + headerExtension.uri + (headerExtension.attributes ? ' ' + headerExtension.attributes : '') + '\r\n';
+};
+
+// Parses a fmtp line, returns dictionary. Sample input:
+// a=fmtp:96 vbr=on;cng=on
+// Also deals with vbr=on; cng=on
+SDPUtils.parseFmtp = function (line) {
+  var parsed = {};
+  var kv = void 0;
+  var parts = line.substring(line.indexOf(' ') + 1).split(';');
+  for (var j = 0; j < parts.length; j++) {
+    kv = parts[j].trim().split('=');
+    parsed[kv[0].trim()] = kv[1];
+  }
+  return parsed;
+};
+
+// Generates a fmtp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeFmtp = function (codec) {
+  var line = '';
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.parameters && Object.keys(codec.parameters).length) {
+    var params = [];
+    Object.keys(codec.parameters).forEach(function (param) {
+      if (codec.parameters[param] !== undefined) {
+        params.push(param + '=' + codec.parameters[param]);
+      } else {
+        params.push(param);
+      }
+    });
+    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
+  }
+  return line;
+};
+
+// Parses a rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
+// a=rtcp-fb:98 nack rpsi
+SDPUtils.parseRtcpFb = function (line) {
+  var parts = line.substring(line.indexOf(' ') + 1).split(' ');
+  return {
+    type: parts.shift(),
+    parameter: parts.join(' ')
+  };
+};
+
+// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeRtcpFb = function (codec) {
+  var lines = '';
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
+    // FIXME: special handling for trr-int?
+    codec.rtcpFeedback.forEach(function (fb) {
+      lines += 'a=rtcp-fb:' + pt + ' ' + fb.type + (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') + '\r\n';
+    });
+  }
+  return lines;
+};
+
+// Parses a RFC 5576 ssrc media attribute. Sample input:
+// a=ssrc:3735928559 cname:something
+SDPUtils.parseSsrcMedia = function (line) {
+  var sp = line.indexOf(' ');
+  var parts = {
+    ssrc: parseInt(line.substring(7, sp), 10)
+  };
+  var colon = line.indexOf(':', sp);
+  if (colon > -1) {
+    parts.attribute = line.substring(sp + 1, colon);
+    parts.value = line.substring(colon + 1);
+  } else {
+    parts.attribute = line.substring(sp + 1);
+  }
+  return parts;
+};
+
+// Parse a ssrc-group line (see RFC 5576). Sample input:
+// a=ssrc-group:semantics 12 34
+SDPUtils.parseSsrcGroup = function (line) {
+  var parts = line.substring(13).split(' ');
+  return {
+    semantics: parts.shift(),
+    ssrcs: parts.map(function (ssrc) {
+      return parseInt(ssrc, 10);
+    })
+  };
+};
+
+// Extracts the MID (RFC 5888) from a media section.
+// Returns the MID or undefined if no mid line was found.
+SDPUtils.getMid = function (mediaSection) {
+  var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
+  if (mid) {
+    return mid.substring(6);
+  }
+};
+
+// Parses a fingerprint line for DTLS-SRTP.
+SDPUtils.parseFingerprint = function (line) {
+  var parts = line.substring(14).split(' ');
+  return {
+    algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
+    value: parts[1].toUpperCase() // the definition is upper-case in RFC 4572.
+  };
+};
+
+// Extracts DTLS parameters from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the fingerprint line as input. See also getIceParameters.
+SDPUtils.getDtlsParameters = function (mediaSection, sessionpart) {
+  var lines = SDPUtils.matchPrefix(mediaSection + sessionpart, 'a=fingerprint:');
+  // Note: a=setup line is ignored since we use the 'auto' role in Edge.
+  return {
+    role: 'auto',
+    fingerprints: lines.map(SDPUtils.parseFingerprint)
+  };
+};
+
+// Serializes DTLS parameters to SDP.
+SDPUtils.writeDtlsParameters = function (params, setupType) {
+  var sdp = 'a=setup:' + setupType + '\r\n';
+  params.fingerprints.forEach(function (fp) {
+    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
+  });
+  return sdp;
+};
+
+// Parses a=crypto lines into
+//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#dictionary-rtcsrtpsdesparameters-members
+SDPUtils.parseCryptoLine = function (line) {
+  var parts = line.substring(9).split(' ');
+  return {
+    tag: parseInt(parts[0], 10),
+    cryptoSuite: parts[1],
+    keyParams: parts[2],
+    sessionParams: parts.slice(3)
+  };
+};
+
+SDPUtils.writeCryptoLine = function (parameters) {
+  return 'a=crypto:' + parameters.tag + ' ' + parameters.cryptoSuite + ' ' + (_typeof(parameters.keyParams) === 'object' ? SDPUtils.writeCryptoKeyParams(parameters.keyParams) : parameters.keyParams) + (parameters.sessionParams ? ' ' + parameters.sessionParams.join(' ') : '') + '\r\n';
+};
+
+// Parses the crypto key parameters into
+//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#rtcsrtpkeyparam*
+SDPUtils.parseCryptoKeyParams = function (keyParams) {
+  if (keyParams.indexOf('inline:') !== 0) {
+    return null;
+  }
+  var parts = keyParams.substring(7).split('|');
+  return {
+    keyMethod: 'inline',
+    keySalt: parts[0],
+    lifeTime: parts[1],
+    mkiValue: parts[2] ? parts[2].split(':')[0] : undefined,
+    mkiLength: parts[2] ? parts[2].split(':')[1] : undefined
+  };
+};
+
+SDPUtils.writeCryptoKeyParams = function (keyParams) {
+  return keyParams.keyMethod + ':' + keyParams.keySalt + (keyParams.lifeTime ? '|' + keyParams.lifeTime : '') + (keyParams.mkiValue && keyParams.mkiLength ? '|' + keyParams.mkiValue + ':' + keyParams.mkiLength : '');
+};
+
+// Extracts all SDES parameters.
+SDPUtils.getCryptoParameters = function (mediaSection, sessionpart) {
+  var lines = SDPUtils.matchPrefix(mediaSection + sessionpart, 'a=crypto:');
+  return lines.map(SDPUtils.parseCryptoLine);
+};
+
+// Parses ICE information from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the ice-ufrag and ice-pwd lines as input.
+SDPUtils.getIceParameters = function (mediaSection, sessionpart) {
+  var ufrag = SDPUtils.matchPrefix(mediaSection + sessionpart, 'a=ice-ufrag:')[0];
+  var pwd = SDPUtils.matchPrefix(mediaSection + sessionpart, 'a=ice-pwd:')[0];
+  if (!(ufrag && pwd)) {
+    return null;
+  }
+  return {
+    usernameFragment: ufrag.substring(12),
+    password: pwd.substring(10)
+  };
+};
+
+// Serializes ICE parameters to SDP.
+SDPUtils.writeIceParameters = function (params) {
+  var sdp = 'a=ice-ufrag:' + params.usernameFragment + '\r\n' + 'a=ice-pwd:' + params.password + '\r\n';
+  if (params.iceLite) {
+    sdp += 'a=ice-lite\r\n';
+  }
+  return sdp;
+};
+
+// Parses the SDP media section and returns RTCRtpParameters.
+SDPUtils.parseRtpParameters = function (mediaSection) {
+  var description = {
+    codecs: [],
+    headerExtensions: [],
+    fecMechanisms: [],
+    rtcp: []
+  };
+  var lines = SDPUtils.splitLines(mediaSection);
+  var mline = lines[0].split(' ');
+  description.profile = mline[2];
+  for (var i = 3; i < mline.length; i++) {
+    // find all codecs from mline[3..]
+    var pt = mline[i];
+    var rtpmapline = SDPUtils.matchPrefix(mediaSection, 'a=rtpmap:' + pt + ' ')[0];
+    if (rtpmapline) {
+      var codec = SDPUtils.parseRtpMap(rtpmapline);
+      var fmtps = SDPUtils.matchPrefix(mediaSection, 'a=fmtp:' + pt + ' ');
+      // Only the first a=fmtp:<pt> is considered.
+      codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
+      codec.rtcpFeedback = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-fb:' + pt + ' ').map(SDPUtils.parseRtcpFb);
+      description.codecs.push(codec);
+      // parse FEC mechanisms from rtpmap lines.
+      switch (codec.name.toUpperCase()) {
+        case 'RED':
+        case 'ULPFEC':
+          description.fecMechanisms.push(codec.name.toUpperCase());
+          break;
+        default:
+          // only RED and ULPFEC are recognized as FEC mechanisms.
+          break;
+      }
+    }
+  }
+  SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function (line) {
+    description.headerExtensions.push(SDPUtils.parseExtmap(line));
+  });
+  var wildcardRtcpFb = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-fb:* ').map(SDPUtils.parseRtcpFb);
+  description.codecs.forEach(function (codec) {
+    wildcardRtcpFb.forEach(function (fb) {
+      var duplicate = codec.rtcpFeedback.find(function (existingFeedback) {
+        return existingFeedback.type === fb.type && existingFeedback.parameter === fb.parameter;
+      });
+      if (!duplicate) {
+        codec.rtcpFeedback.push(fb);
+      }
+    });
+  });
+  // FIXME: parse rtcp.
+  return description;
+};
+
+// Generates parts of the SDP media section describing the capabilities /
+// parameters.
+SDPUtils.writeRtpDescription = function (kind, caps) {
+  var sdp = '';
+
+  // Build the mline.
+  sdp += 'm=' + kind + ' ';
+  sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
+  sdp += ' ' + (caps.profile || 'UDP/TLS/RTP/SAVPF') + ' ';
+  sdp += caps.codecs.map(function (codec) {
+    if (codec.preferredPayloadType !== undefined) {
+      return codec.preferredPayloadType;
+    }
+    return codec.payloadType;
+  }).join(' ') + '\r\n';
+
+  sdp += 'c=IN IP4 0.0.0.0\r\n';
+  sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';
+
+  // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
+  caps.codecs.forEach(function (codec) {
+    sdp += SDPUtils.writeRtpMap(codec);
+    sdp += SDPUtils.writeFmtp(codec);
+    sdp += SDPUtils.writeRtcpFb(codec);
+  });
+  var maxptime = 0;
+  caps.codecs.forEach(function (codec) {
+    if (codec.maxptime > maxptime) {
+      maxptime = codec.maxptime;
+    }
+  });
+  if (maxptime > 0) {
+    sdp += 'a=maxptime:' + maxptime + '\r\n';
+  }
+
+  if (caps.headerExtensions) {
+    caps.headerExtensions.forEach(function (extension) {
+      sdp += SDPUtils.writeExtmap(extension);
+    });
+  }
+  // FIXME: write fecMechanisms.
+  return sdp;
+};
+
+// Parses the SDP media section and returns an array of
+// RTCRtpEncodingParameters.
+SDPUtils.parseRtpEncodingParameters = function (mediaSection) {
+  var encodingParameters = [];
+  var description = SDPUtils.parseRtpParameters(mediaSection);
+  var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
+  var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;
+
+  // filter a=ssrc:... cname:, ignore PlanB-msid
+  var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:').map(function (line) {
+    return SDPUtils.parseSsrcMedia(line);
+  }).filter(function (parts) {
+    return parts.attribute === 'cname';
+  });
+  var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
+  var secondarySsrc = void 0;
+
+  var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID').map(function (line) {
+    var parts = line.substring(17).split(' ');
+    return parts.map(function (part) {
+      return parseInt(part, 10);
+    });
+  });
+  if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
+    secondarySsrc = flows[0][1];
+  }
+
+  description.codecs.forEach(function (codec) {
+    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
+      var encParam = {
+        ssrc: primarySsrc,
+        codecPayloadType: parseInt(codec.parameters.apt, 10)
+      };
+      if (primarySsrc && secondarySsrc) {
+        encParam.rtx = { ssrc: secondarySsrc };
+      }
+      encodingParameters.push(encParam);
+      if (hasRed) {
+        encParam = JSON.parse(JSON.stringify(encParam));
+        encParam.fec = {
+          ssrc: primarySsrc,
+          mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
+        };
+        encodingParameters.push(encParam);
+      }
+    }
+  });
+  if (encodingParameters.length === 0 && primarySsrc) {
+    encodingParameters.push({
+      ssrc: primarySsrc
+    });
+  }
+
+  // we support both b=AS and b=TIAS but interpret AS as TIAS.
+  var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
+  if (bandwidth.length) {
+    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
+      bandwidth = parseInt(bandwidth[0].substring(7), 10);
+    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
+      // use formula from JSEP to convert b=AS to TIAS value.
+      bandwidth = parseInt(bandwidth[0].substring(5), 10) * 1000 * 0.95 - 50 * 40 * 8;
+    } else {
+      bandwidth = undefined;
+    }
+    encodingParameters.forEach(function (params) {
+      params.maxBitrate = bandwidth;
+    });
+  }
+  return encodingParameters;
+};
+
+// parses http://draft.ortc.org/#rtcrtcpparameters*
+SDPUtils.parseRtcpParameters = function (mediaSection) {
+  var rtcpParameters = {};
+
+  // Gets the first SSRC. Note that with RTX there might be multiple
+  // SSRCs.
+  var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:').map(function (line) {
+    return SDPUtils.parseSsrcMedia(line);
+  }).filter(function (obj) {
+    return obj.attribute === 'cname';
+  })[0];
+  if (remoteSsrc) {
+    rtcpParameters.cname = remoteSsrc.value;
+    rtcpParameters.ssrc = remoteSsrc.ssrc;
+  }
+
+  // Edge uses the compound attribute instead of reducedSize
+  // compound is !reducedSize
+  var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
+  rtcpParameters.reducedSize = rsize.length > 0;
+  rtcpParameters.compound = rsize.length === 0;
+
+  // parses the rtcp-mux attrіbute.
+  // Note that Edge does not support unmuxed RTCP.
+  var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
+  rtcpParameters.mux = mux.length > 0;
+
+  return rtcpParameters;
+};
+
+SDPUtils.writeRtcpParameters = function (rtcpParameters) {
+  var sdp = '';
+  if (rtcpParameters.reducedSize) {
+    sdp += 'a=rtcp-rsize\r\n';
+  }
+  if (rtcpParameters.mux) {
+    sdp += 'a=rtcp-mux\r\n';
+  }
+  if (rtcpParameters.ssrc !== undefined && rtcpParameters.cname) {
+    sdp += 'a=ssrc:' + rtcpParameters.ssrc + ' cname:' + rtcpParameters.cname + '\r\n';
+  }
+  return sdp;
+};
+
+// parses either a=msid: or a=ssrc:... msid lines and returns
+// the id of the MediaStream and MediaStreamTrack.
+SDPUtils.parseMsid = function (mediaSection) {
+  var parts = void 0;
+  var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
+  if (spec.length === 1) {
+    parts = spec[0].substring(7).split(' ');
+    return { stream: parts[0], track: parts[1] };
+  }
+  var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:').map(function (line) {
+    return SDPUtils.parseSsrcMedia(line);
+  }).filter(function (msidParts) {
+    return msidParts.attribute === 'msid';
+  });
+  if (planB.length > 0) {
+    parts = planB[0].value.split(' ');
+    return { stream: parts[0], track: parts[1] };
+  }
+};
+
+// SCTP
+// parses draft-ietf-mmusic-sctp-sdp-26 first and falls back
+// to draft-ietf-mmusic-sctp-sdp-05
+SDPUtils.parseSctpDescription = function (mediaSection) {
+  var mline = SDPUtils.parseMLine(mediaSection);
+  var maxSizeLine = SDPUtils.matchPrefix(mediaSection, 'a=max-message-size:');
+  var maxMessageSize = void 0;
+  if (maxSizeLine.length > 0) {
+    maxMessageSize = parseInt(maxSizeLine[0].substring(19), 10);
+  }
+  if (isNaN(maxMessageSize)) {
+    maxMessageSize = 65536;
+  }
+  var sctpPort = SDPUtils.matchPrefix(mediaSection, 'a=sctp-port:');
+  if (sctpPort.length > 0) {
+    return {
+      port: parseInt(sctpPort[0].substring(12), 10),
+      protocol: mline.fmt,
+      maxMessageSize: maxMessageSize
+    };
+  }
+  var sctpMapLines = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:');
+  if (sctpMapLines.length > 0) {
+    var parts = sctpMapLines[0].substring(10).split(' ');
+    return {
+      port: parseInt(parts[0], 10),
+      protocol: parts[1],
+      maxMessageSize: maxMessageSize
+    };
+  }
+};
+
+// SCTP
+// outputs the draft-ietf-mmusic-sctp-sdp-26 version that all browsers
+// support by now receiving in this format, unless we originally parsed
+// as the draft-ietf-mmusic-sctp-sdp-05 format (indicated by the m-line
+// protocol of DTLS/SCTP -- without UDP/ or TCP/)
+SDPUtils.writeSctpDescription = function (media, sctp) {
+  var output = [];
+  if (media.protocol !== 'DTLS/SCTP') {
+    output = ['m=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.protocol + '\r\n', 'c=IN IP4 0.0.0.0\r\n', 'a=sctp-port:' + sctp.port + '\r\n'];
+  } else {
+    output = ['m=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.port + '\r\n', 'c=IN IP4 0.0.0.0\r\n', 'a=sctpmap:' + sctp.port + ' ' + sctp.protocol + ' 65535\r\n'];
+  }
+  if (sctp.maxMessageSize !== undefined) {
+    output.push('a=max-message-size:' + sctp.maxMessageSize + '\r\n');
+  }
+  return output.join('');
+};
+
+// Generate a session ID for SDP.
+// https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
+// recommends using a cryptographically random +ve 64-bit value
+// but right now this should be acceptable and within the right range
+SDPUtils.generateSessionId = function () {
+  return Math.random().toString().substr(2, 22);
+};
+
+// Write boiler plate for start of SDP
+// sessId argument is optional - if not supplied it will
+// be generated randomly
+// sessVersion is optional and defaults to 2
+// sessUser is optional and defaults to 'thisisadapterortc'
+SDPUtils.writeSessionBoilerplate = function (sessId, sessVer, sessUser) {
+  var sessionId = void 0;
+  var version = sessVer !== undefined ? sessVer : 2;
+  if (sessId) {
+    sessionId = sessId;
+  } else {
+    sessionId = SDPUtils.generateSessionId();
+  }
+  var user = sessUser || 'thisisadapterortc';
+  // FIXME: sess-id should be an NTP timestamp.
+  return 'v=0\r\n' + 'o=' + user + ' ' + sessionId + ' ' + version + ' IN IP4 127.0.0.1\r\n' + 's=-\r\n' + 't=0 0\r\n';
+};
+
+// Gets the direction from the mediaSection or the sessionpart.
+SDPUtils.getDirection = function (mediaSection, sessionpart) {
+  // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
+  var lines = SDPUtils.splitLines(mediaSection);
+  for (var i = 0; i < lines.length; i++) {
+    switch (lines[i]) {
+      case 'a=sendrecv':
+      case 'a=sendonly':
+      case 'a=recvonly':
+      case 'a=inactive':
+        return lines[i].substring(2);
+      default:
+      // FIXME: What should happen here?
+    }
+  }
+  if (sessionpart) {
+    return SDPUtils.getDirection(sessionpart);
+  }
+  return 'sendrecv';
+};
+
+SDPUtils.getKind = function (mediaSection) {
+  var lines = SDPUtils.splitLines(mediaSection);
+  var mline = lines[0].split(' ');
+  return mline[0].substring(2);
+};
+
+SDPUtils.isRejected = function (mediaSection) {
+  return mediaSection.split(' ', 2)[1] === '0';
+};
+
+SDPUtils.parseMLine = function (mediaSection) {
+  var lines = SDPUtils.splitLines(mediaSection);
+  var parts = lines[0].substring(2).split(' ');
+  return {
+    kind: parts[0],
+    port: parseInt(parts[1], 10),
+    protocol: parts[2],
+    fmt: parts.slice(3).join(' ')
+  };
+};
+
+SDPUtils.parseOLine = function (mediaSection) {
+  var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
+  var parts = line.substring(2).split(' ');
+  return {
+    username: parts[0],
+    sessionId: parts[1],
+    sessionVersion: parseInt(parts[2], 10),
+    netType: parts[3],
+    addressType: parts[4],
+    address: parts[5]
+  };
+};
+
+// a very naive interpretation of a valid SDP.
+SDPUtils.isValidSDP = function (blob) {
+  if (typeof blob !== 'string' || blob.length === 0) {
+    return false;
+  }
+  var lines = SDPUtils.splitLines(blob);
+  for (var i = 0; i < lines.length; i++) {
+    if (lines[i].length < 2 || lines[i].charAt(1) !== '=') {
+      return false;
+    }
+    // TODO: check the modifier a bit more.
+  }
+  return true;
+};
+
+// Expose public methods.
+if ((typeof module === 'undefined' ? 'undefined' : _typeof(module)) === 'object') {
+  module.exports = SDPUtils;
+}

node_modules/sdp/package.json

@@ -0,0 +1,36 @@
+{
+  "name": "sdp",
+  "version": "3.2.0",
+  "description": "SDP parsing and serialization utilities",
+  "main": "dist/sdp.js",
+  "module": "sdp.js",
+  "typings": "sdp.d.ts",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/fippo/sdp.git"
+  },
+  "scripts": {
+    "build": "babel sdp.js --presets babel-preset-env --out-dir dist",
+    "coverage": "c8 report --reporter=text-lcov > coverage.lcov",
+    "prepare": "npm run build",
+    "test": "eslint sdp.js test/sdp.js && c8 --reporter html mocha test/sdp.js"
+  },
+  "keywords": [
+    "sdp",
+    "webrtc"
+  ],
+  "author": "Philipp Hancke",
+  "license": "MIT",
+  "devDependencies": {
+    "babel-cli": "^6.26.0",
+    "babel-core": "^6.26.3",
+    "babel-preset-env": "^1.7.0",
+    "c8": "^7.12.0",
+    "chai": "^4.3.7",
+    "codecov": "^3.6.5",
+    "eslint": "^8.31.0",
+    "mocha": "^10.2.0",
+    "sinon": "^15.0.1",
+    "sinon-chai": "^3.7.0"
+  }
+}

node_modules/sdp/sdp.d.ts

@@ -0,0 +1,220 @@
+export type SDPBlob = string;
+export type SDPLine = string;
+export type SDPSection = string;
+
+export type SDPDirection = 'sendonly' | 'recvonly' | 'sendrecv' | 'inactive';
+
+export interface SDPIceCandidate {
+    foundation: string;
+    component: 'rtp' | 'rtcp' | number;
+    protocol: 'tcp' | 'udp';
+    priority: number;
+    ip: string;
+    address: string;
+    port: number;
+    type: 'host' | 'prflx' | 'srflx' | 'relay';
+    relatedAddress?: string;
+    relatedPort?: number;
+    tcpType?: string;
+    ufrag?: string;
+    usernameFragment?: string;
+}
+
+export interface SDPIceParameters {
+    iceLite?: boolean;
+    usernameFragment: string;
+    password: string;
+}
+
+export interface SDPCodecParameters {
+    payloadType: number;
+    preferredPayloadType?: number;
+    name: string;
+    clockRate: number;
+    channels: number;
+    numChannels?: number;
+    maxptime?: number;
+}
+
+export interface SDPCodecAdditionalParameters {
+    [key: string]: string;
+}
+
+export interface SDPHeaderExtension {
+    id: number;
+    direction?: SDPDirection;
+    uri: string;
+    atrributes: string | undefined;
+}
+
+export interface SDPFeedbackParameter {
+    type: string;
+    parameter: string;
+}
+
+export interface SDPFingerprint {
+    algorithm: string;
+    value: string;
+}
+
+export interface SDPDtlsParameters {
+    role: string;
+    fingerprints: SDPFingerprint[];
+}
+
+export interface SDPMediaSource {
+    ssrc: number;
+    attribute?: string;
+    value?: string;
+}
+
+export interface SDPMediaSourceGroup {
+    semantics: string;
+    ssrcs: number[];
+}
+
+export interface SDPMediaStreamId {
+    stream: string;
+    track: string;
+}
+
+export interface SDPCodec extends SDPCodecParameters {
+    payloadType: number;
+    preferredPayloadType?: number;
+    parameters?: SDPCodecAdditionalParameters;
+    rtcpFeedback?: SDPFeedbackParameter[];
+}
+
+export interface SDPGroup {
+    semantics: string;
+    mids: string[];
+}
+
+export interface SDPMLine {
+    kind: string;
+    port?: number;
+    protocol: string;
+    fmt?: string;
+}
+
+export interface SDPOLine {
+    username: string;
+    sessionId: string;
+    sessionVersion: number;
+    netType: string;
+    addressType: string;
+    address: string;
+}
+
+export interface SDPRtcpParameters {
+    cname?: string;
+    ssrc?: number;
+    reducedSize?: boolean;
+    compound?: boolean;
+    mux?: boolean;
+}
+
+export interface SDPEncodingParameters {
+    ssrc: number;
+    codecPayloadType?: number;
+    rtx?: {
+        ssrc: number;
+    };
+    fec?: {
+        ssrc: number;
+        mechanism: string;
+    };
+}
+
+export interface SDPRtpCapabilities {
+    codecs: SDPCodec[];
+    headerExtensions: SDPHeaderExtension[];
+    fecMechanisms: string[];
+    rtcp?: SDPRtcpParameters[];
+}
+
+export interface SDPSctpDescription {
+    port: number;
+    protocol: string;
+    maxMessageSize?: number;
+}
+
+export const localCname: string;
+
+export function generateIdentifier(): string;
+
+export function splitLines(blob: SDPBlob): SDPLine[];
+export function splitSections(blob: SDPBlob): SDPSection[];
+
+export function getDescription(blob: SDPBlob): SDPSection;
+export function getMediaSections(blob: SDPBlob): SDPSection[];
+
+export function matchPrefix(blob: SDPBlob, prefix: string): SDPLine[];
+
+export function parseCandidate(line: SDPLine): SDPIceCandidate;
+export function writeCandidate(candidate: SDPIceCandidate): SDPLine;
+
+export function parseIceOptions(line: SDPLine): string[];
+
+export function parseRtpMap(line: SDPLine): SDPCodecParameters;
+export function writeRtpMap(codec: SDPCodecParameters): SDPLine;
+
+export function parseExtmap(line: SDPLine): SDPHeaderExtension;
+export function writeExtmap(headerExtension: SDPHeaderExtension): SDPLine;
+
+export function parseFmtp(line: SDPLine): SDPCodecAdditionalParameters;
+export function writeFmtp(codec: SDPCodec): SDPLine;
+
+export function parseRtcpFb(line: SDPLine): SDPFeedbackParameter;
+export function writeRtcpFb(codec: SDPCodec): SDPLine[];
+
+export function parseSsrcMedia(line: SDPLine): SDPMediaSource;
+export function parseSsrcGroup(line: SDPLine): SDPMediaSourceGroup;
+
+export function getMid(mediaSection: SDPSection): string;
+
+export function parseFingerprint(line: SDPLine): SDPFingerprint;
+
+export function getDtlsParameters(
+    mediaSection: SDPSection,
+    session: SDPSection
+): SDPDtlsParameters;
+export function writeDtlsParameters(params: SDPDtlsParameters, setupType: string): SDPLine;
+
+export function getIceParameters(
+    mediaSection: SDPSection,
+    session: SDPSection
+): SDPIceParameters;
+export function writeIceParameters(params: SDPIceParameters): SDPLine;
+
+export function parseRtpParameters(mediaSection: SDPSection): SDPRtpCapabilities;
+export function writeRtpDescription(kind: string, caps: SDPRtpCapabilities): SDPSection;
+
+export function parseRtpEncodingParameters(mediaSection: SDPSection): SDPEncodingParameters[];
+
+export function parseRtcpParameters(mediaSection: SDPSection): SDPRtcpParameters;
+export function writeRtcpParameters(params: SDPRtcpParameters): SDPLine;
+
+export function parseMsid(mediaSection: SDPSection): SDPMediaStreamId;
+
+export function parseSctpDescription(mediaSection: SDPSection): SDPSctpDescription;
+export function writeSctpDescription(
+    mediaSection: SDPMLine,
+    desc: SDPSctpDescription
+): SDPSection;
+
+export function generateSessionId(): string;
+export function writeSessionBoilerplate(
+    sessId?: string,
+    sessVer?: number,
+    sessUser?: string
+): SDPBlob;
+
+export function getDirection(mediaSection: SDPSection, sessionpart: SDPSection): SDPDirection;
+export function getKind(mediaSection: SDPSection): string;
+export function isRejected(mediaSection: SDPSection): boolean;
+
+export function parseMLine(mediaSection: SDPSection): SDPMLine;
+export function parseOLine(mediaSection: SDPSection): SDPOLine;
+
+export function isValidSDP(blob: SDPBlob): boolean;

node_modules/sdp/sdp.js

@@ -0,0 +1,802 @@
+/* eslint-env node */
+'use strict';
+
+// SDP helpers.
+const SDPUtils = {};
+
+// Generate an alphanumeric identifier for cname or mids.
+// TODO: use UUIDs instead? https://gist.github.com/jed/982883
+SDPUtils.generateIdentifier = function() {
+  return Math.random().toString(36).substring(2, 12);
+};
+
+// The RTCP CNAME used by all peerconnections from the same JS.
+SDPUtils.localCName = SDPUtils.generateIdentifier();
+
+// Splits SDP into lines, dealing with both CRLF and LF.
+SDPUtils.splitLines = function(blob) {
+  return blob.trim().split('\n').map(line => line.trim());
+};
+// Splits SDP into sessionpart and mediasections. Ensures CRLF.
+SDPUtils.splitSections = function(blob) {
+  const parts = blob.split('\nm=');
+  return parts.map((part, index) => (index > 0 ?
+    'm=' + part : part).trim() + '\r\n');
+};
+
+// Returns the session description.
+SDPUtils.getDescription = function(blob) {
+  const sections = SDPUtils.splitSections(blob);
+  return sections && sections[0];
+};
+
+// Returns the individual media sections.
+SDPUtils.getMediaSections = function(blob) {
+  const sections = SDPUtils.splitSections(blob);
+  sections.shift();
+  return sections;
+};
+
+// Returns lines that start with a certain prefix.
+SDPUtils.matchPrefix = function(blob, prefix) {
+  return SDPUtils.splitLines(blob).filter(line => line.indexOf(prefix) === 0);
+};
+
+// Parses an ICE candidate line. Sample input:
+// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
+// rport 55996"
+// Input can be prefixed with a=.
+SDPUtils.parseCandidate = function(line) {
+  let parts;
+  // Parse both variants.
+  if (line.indexOf('a=candidate:') === 0) {
+    parts = line.substring(12).split(' ');
+  } else {
+    parts = line.substring(10).split(' ');
+  }
+
+  const candidate = {
+    foundation: parts[0],
+    component: {1: 'rtp', 2: 'rtcp'}[parts[1]] || parts[1],
+    protocol: parts[2].toLowerCase(),
+    priority: parseInt(parts[3], 10),
+    ip: parts[4],
+    address: parts[4], // address is an alias for ip.
+    port: parseInt(parts[5], 10),
+    // skip parts[6] == 'typ'
+    type: parts[7],
+  };
+
+  for (let i = 8; i < parts.length; i += 2) {
+    switch (parts[i]) {
+      case 'raddr':
+        candidate.relatedAddress = parts[i + 1];
+        break;
+      case 'rport':
+        candidate.relatedPort = parseInt(parts[i + 1], 10);
+        break;
+      case 'tcptype':
+        candidate.tcpType = parts[i + 1];
+        break;
+      case 'ufrag':
+        candidate.ufrag = parts[i + 1]; // for backward compatibility.
+        candidate.usernameFragment = parts[i + 1];
+        break;
+      default: // extension handling, in particular ufrag. Don't overwrite.
+        if (candidate[parts[i]] === undefined) {
+          candidate[parts[i]] = parts[i + 1];
+        }
+        break;
+    }
+  }
+  return candidate;
+};
+
+// Translates a candidate object into SDP candidate attribute.
+// This does not include the a= prefix!
+SDPUtils.writeCandidate = function(candidate) {
+  const sdp = [];
+  sdp.push(candidate.foundation);
+
+  const component = candidate.component;
+  if (component === 'rtp') {
+    sdp.push(1);
+  } else if (component === 'rtcp') {
+    sdp.push(2);
+  } else {
+    sdp.push(component);
+  }
+  sdp.push(candidate.protocol.toUpperCase());
+  sdp.push(candidate.priority);
+  sdp.push(candidate.address || candidate.ip);
+  sdp.push(candidate.port);
+
+  const type = candidate.type;
+  sdp.push('typ');
+  sdp.push(type);
+  if (type !== 'host' && candidate.relatedAddress &&
+      candidate.relatedPort) {
+    sdp.push('raddr');
+    sdp.push(candidate.relatedAddress);
+    sdp.push('rport');
+    sdp.push(candidate.relatedPort);
+  }
+  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
+    sdp.push('tcptype');
+    sdp.push(candidate.tcpType);
+  }
+  if (candidate.usernameFragment || candidate.ufrag) {
+    sdp.push('ufrag');
+    sdp.push(candidate.usernameFragment || candidate.ufrag);
+  }
+  return 'candidate:' + sdp.join(' ');
+};
+
+// Parses an ice-options line, returns an array of option tags.
+// Sample input:
+// a=ice-options:foo bar
+SDPUtils.parseIceOptions = function(line) {
+  return line.substring(14).split(' ');
+};
+
+// Parses a rtpmap line, returns RTCRtpCoddecParameters. Sample input:
+// a=rtpmap:111 opus/48000/2
+SDPUtils.parseRtpMap = function(line) {
+  let parts = line.substring(9).split(' ');
+  const parsed = {
+    payloadType: parseInt(parts.shift(), 10), // was: id
+  };
+
+  parts = parts[0].split('/');
+
+  parsed.name = parts[0];
+  parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
+  parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
+  // legacy alias, got renamed back to channels in ORTC.
+  parsed.numChannels = parsed.channels;
+  return parsed;
+};
+
+// Generates a rtpmap line from RTCRtpCodecCapability or
+// RTCRtpCodecParameters.
+SDPUtils.writeRtpMap = function(codec) {
+  let pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  const channels = codec.channels || codec.numChannels || 1;
+  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
+      (channels !== 1 ? '/' + channels : '') + '\r\n';
+};
+
+// Parses a extmap line (headerextension from RFC 5285). Sample input:
+// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
+// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
+SDPUtils.parseExtmap = function(line) {
+  const parts = line.substring(9).split(' ');
+  return {
+    id: parseInt(parts[0], 10),
+    direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
+    uri: parts[1],
+    attributes: parts.slice(2).join(' '),
+  };
+};
+
+// Generates an extmap line from RTCRtpHeaderExtensionParameters or
+// RTCRtpHeaderExtension.
+SDPUtils.writeExtmap = function(headerExtension) {
+  return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
+      (headerExtension.direction && headerExtension.direction !== 'sendrecv'
+        ? '/' + headerExtension.direction
+        : '') +
+      ' ' + headerExtension.uri +
+      (headerExtension.attributes ? ' ' + headerExtension.attributes : '') +
+      '\r\n';
+};
+
+// Parses a fmtp line, returns dictionary. Sample input:
+// a=fmtp:96 vbr=on;cng=on
+// Also deals with vbr=on; cng=on
+SDPUtils.parseFmtp = function(line) {
+  const parsed = {};
+  let kv;
+  const parts = line.substring(line.indexOf(' ') + 1).split(';');
+  for (let j = 0; j < parts.length; j++) {
+    kv = parts[j].trim().split('=');
+    parsed[kv[0].trim()] = kv[1];
+  }
+  return parsed;
+};
+
+// Generates a fmtp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeFmtp = function(codec) {
+  let line = '';
+  let pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.parameters && Object.keys(codec.parameters).length) {
+    const params = [];
+    Object.keys(codec.parameters).forEach(param => {
+      if (codec.parameters[param] !== undefined) {
+        params.push(param + '=' + codec.parameters[param]);
+      } else {
+        params.push(param);
+      }
+    });
+    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
+  }
+  return line;
+};
+
+// Parses a rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
+// a=rtcp-fb:98 nack rpsi
+SDPUtils.parseRtcpFb = function(line) {
+  const parts = line.substring(line.indexOf(' ') + 1).split(' ');
+  return {
+    type: parts.shift(),
+    parameter: parts.join(' '),
+  };
+};
+
+// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeRtcpFb = function(codec) {
+  let lines = '';
+  let pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
+    // FIXME: special handling for trr-int?
+    codec.rtcpFeedback.forEach(fb => {
+      lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
+      (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
+          '\r\n';
+    });
+  }
+  return lines;
+};
+
+// Parses a RFC 5576 ssrc media attribute. Sample input:
+// a=ssrc:3735928559 cname:something
+SDPUtils.parseSsrcMedia = function(line) {
+  const sp = line.indexOf(' ');
+  const parts = {
+    ssrc: parseInt(line.substring(7, sp), 10),
+  };
+  const colon = line.indexOf(':', sp);
+  if (colon > -1) {
+    parts.attribute = line.substring(sp + 1, colon);
+    parts.value = line.substring(colon + 1);
+  } else {
+    parts.attribute = line.substring(sp + 1);
+  }
+  return parts;
+};
+
+// Parse a ssrc-group line (see RFC 5576). Sample input:
+// a=ssrc-group:semantics 12 34
+SDPUtils.parseSsrcGroup = function(line) {
+  const parts = line.substring(13).split(' ');
+  return {
+    semantics: parts.shift(),
+    ssrcs: parts.map(ssrc => parseInt(ssrc, 10)),
+  };
+};
+
+// Extracts the MID (RFC 5888) from a media section.
+// Returns the MID or undefined if no mid line was found.
+SDPUtils.getMid = function(mediaSection) {
+  const mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
+  if (mid) {
+    return mid.substring(6);
+  }
+};
+
+// Parses a fingerprint line for DTLS-SRTP.
+SDPUtils.parseFingerprint = function(line) {
+  const parts = line.substring(14).split(' ');
+  return {
+    algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
+    value: parts[1].toUpperCase(), // the definition is upper-case in RFC 4572.
+  };
+};
+
+// Extracts DTLS parameters from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the fingerprint line as input. See also getIceParameters.
+SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
+  const lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=fingerprint:');
+  // Note: a=setup line is ignored since we use the 'auto' role in Edge.
+  return {
+    role: 'auto',
+    fingerprints: lines.map(SDPUtils.parseFingerprint),
+  };
+};
+
+// Serializes DTLS parameters to SDP.
+SDPUtils.writeDtlsParameters = function(params, setupType) {
+  let sdp = 'a=setup:' + setupType + '\r\n';
+  params.fingerprints.forEach(fp => {
+    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
+  });
+  return sdp;
+};
+
+// Parses a=crypto lines into
+//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#dictionary-rtcsrtpsdesparameters-members
+SDPUtils.parseCryptoLine = function(line) {
+  const parts = line.substring(9).split(' ');
+  return {
+    tag: parseInt(parts[0], 10),
+    cryptoSuite: parts[1],
+    keyParams: parts[2],
+    sessionParams: parts.slice(3),
+  };
+};
+
+SDPUtils.writeCryptoLine = function(parameters) {
+  return 'a=crypto:' + parameters.tag + ' ' +
+    parameters.cryptoSuite + ' ' +
+    (typeof parameters.keyParams === 'object'
+      ? SDPUtils.writeCryptoKeyParams(parameters.keyParams)
+      : parameters.keyParams) +
+    (parameters.sessionParams ? ' ' + parameters.sessionParams.join(' ') : '') +
+    '\r\n';
+};
+
+// Parses the crypto key parameters into
+//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#rtcsrtpkeyparam*
+SDPUtils.parseCryptoKeyParams = function(keyParams) {
+  if (keyParams.indexOf('inline:') !== 0) {
+    return null;
+  }
+  const parts = keyParams.substring(7).split('|');
+  return {
+    keyMethod: 'inline',
+    keySalt: parts[0],
+    lifeTime: parts[1],
+    mkiValue: parts[2] ? parts[2].split(':')[0] : undefined,
+    mkiLength: parts[2] ? parts[2].split(':')[1] : undefined,
+  };
+};
+
+SDPUtils.writeCryptoKeyParams = function(keyParams) {
+  return keyParams.keyMethod + ':'
+    + keyParams.keySalt +
+    (keyParams.lifeTime ? '|' + keyParams.lifeTime : '') +
+    (keyParams.mkiValue && keyParams.mkiLength
+      ? '|' + keyParams.mkiValue + ':' + keyParams.mkiLength
+      : '');
+};
+
+// Extracts all SDES parameters.
+SDPUtils.getCryptoParameters = function(mediaSection, sessionpart) {
+  const lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=crypto:');
+  return lines.map(SDPUtils.parseCryptoLine);
+};
+
+// Parses ICE information from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the ice-ufrag and ice-pwd lines as input.
+SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
+  const ufrag = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=ice-ufrag:')[0];
+  const pwd = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=ice-pwd:')[0];
+  if (!(ufrag && pwd)) {
+    return null;
+  }
+  return {
+    usernameFragment: ufrag.substring(12),
+    password: pwd.substring(10),
+  };
+};
+
+// Serializes ICE parameters to SDP.
+SDPUtils.writeIceParameters = function(params) {
+  let sdp = 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
+      'a=ice-pwd:' + params.password + '\r\n';
+  if (params.iceLite) {
+    sdp += 'a=ice-lite\r\n';
+  }
+  return sdp;
+};
+
+// Parses the SDP media section and returns RTCRtpParameters.
+SDPUtils.parseRtpParameters = function(mediaSection) {
+  const description = {
+    codecs: [],
+    headerExtensions: [],
+    fecMechanisms: [],
+    rtcp: [],
+  };
+  const lines = SDPUtils.splitLines(mediaSection);
+  const mline = lines[0].split(' ');
+  description.profile = mline[2];
+  for (let i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
+    const pt = mline[i];
+    const rtpmapline = SDPUtils.matchPrefix(
+      mediaSection, 'a=rtpmap:' + pt + ' ')[0];
+    if (rtpmapline) {
+      const codec = SDPUtils.parseRtpMap(rtpmapline);
+      const fmtps = SDPUtils.matchPrefix(
+        mediaSection, 'a=fmtp:' + pt + ' ');
+      // Only the first a=fmtp:<pt> is considered.
+      codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
+      codec.rtcpFeedback = SDPUtils.matchPrefix(
+        mediaSection, 'a=rtcp-fb:' + pt + ' ')
+        .map(SDPUtils.parseRtcpFb);
+      description.codecs.push(codec);
+      // parse FEC mechanisms from rtpmap lines.
+      switch (codec.name.toUpperCase()) {
+        case 'RED':
+        case 'ULPFEC':
+          description.fecMechanisms.push(codec.name.toUpperCase());
+          break;
+        default: // only RED and ULPFEC are recognized as FEC mechanisms.
+          break;
+      }
+    }
+  }
+  SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(line => {
+    description.headerExtensions.push(SDPUtils.parseExtmap(line));
+  });
+  const wildcardRtcpFb = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-fb:* ')
+    .map(SDPUtils.parseRtcpFb);
+  description.codecs.forEach(codec => {
+    wildcardRtcpFb.forEach(fb=> {
+      const duplicate = codec.rtcpFeedback.find(existingFeedback => {
+        return existingFeedback.type === fb.type &&
+          existingFeedback.parameter === fb.parameter;
+      });
+      if (!duplicate) {
+        codec.rtcpFeedback.push(fb);
+      }
+    });
+  });
+  // FIXME: parse rtcp.
+  return description;
+};
+
+// Generates parts of the SDP media section describing the capabilities /
+// parameters.
+SDPUtils.writeRtpDescription = function(kind, caps) {
+  let sdp = '';
+
+  // Build the mline.
+  sdp += 'm=' + kind + ' ';
+  sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
+  sdp += ' ' + (caps.profile || 'UDP/TLS/RTP/SAVPF') + ' ';
+  sdp += caps.codecs.map(codec => {
+    if (codec.preferredPayloadType !== undefined) {
+      return codec.preferredPayloadType;
+    }
+    return codec.payloadType;
+  }).join(' ') + '\r\n';
+
+  sdp += 'c=IN IP4 0.0.0.0\r\n';
+  sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';
+
+  // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
+  caps.codecs.forEach(codec => {
+    sdp += SDPUtils.writeRtpMap(codec);
+    sdp += SDPUtils.writeFmtp(codec);
+    sdp += SDPUtils.writeRtcpFb(codec);
+  });
+  let maxptime = 0;
+  caps.codecs.forEach(codec => {
+    if (codec.maxptime > maxptime) {
+      maxptime = codec.maxptime;
+    }
+  });
+  if (maxptime > 0) {
+    sdp += 'a=maxptime:' + maxptime + '\r\n';
+  }
+
+  if (caps.headerExtensions) {
+    caps.headerExtensions.forEach(extension => {
+      sdp += SDPUtils.writeExtmap(extension);
+    });
+  }
+  // FIXME: write fecMechanisms.
+  return sdp;
+};
+
+// Parses the SDP media section and returns an array of
+// RTCRtpEncodingParameters.
+SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
+  const encodingParameters = [];
+  const description = SDPUtils.parseRtpParameters(mediaSection);
+  const hasRed = description.fecMechanisms.indexOf('RED') !== -1;
+  const hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;
+
+  // filter a=ssrc:... cname:, ignore PlanB-msid
+  const ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+    .map(line => SDPUtils.parseSsrcMedia(line))
+    .filter(parts => parts.attribute === 'cname');
+  const primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
+  let secondarySsrc;
+
+  const flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
+    .map(line => {
+      const parts = line.substring(17).split(' ');
+      return parts.map(part => parseInt(part, 10));
+    });
+  if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
+    secondarySsrc = flows[0][1];
+  }
+
+  description.codecs.forEach(codec => {
+    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
+      let encParam = {
+        ssrc: primarySsrc,
+        codecPayloadType: parseInt(codec.parameters.apt, 10),
+      };
+      if (primarySsrc && secondarySsrc) {
+        encParam.rtx = {ssrc: secondarySsrc};
+      }
+      encodingParameters.push(encParam);
+      if (hasRed) {
+        encParam = JSON.parse(JSON.stringify(encParam));
+        encParam.fec = {
+          ssrc: primarySsrc,
+          mechanism: hasUlpfec ? 'red+ulpfec' : 'red',
+        };
+        encodingParameters.push(encParam);
+      }
+    }
+  });
+  if (encodingParameters.length === 0 && primarySsrc) {
+    encodingParameters.push({
+      ssrc: primarySsrc,
+    });
+  }
+
+  // we support both b=AS and b=TIAS but interpret AS as TIAS.
+  let bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
+  if (bandwidth.length) {
+    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
+      bandwidth = parseInt(bandwidth[0].substring(7), 10);
+    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
+      // use formula from JSEP to convert b=AS to TIAS value.
+      bandwidth = parseInt(bandwidth[0].substring(5), 10) * 1000 * 0.95
+          - (50 * 40 * 8);
+    } else {
+      bandwidth = undefined;
+    }
+    encodingParameters.forEach(params => {
+      params.maxBitrate = bandwidth;
+    });
+  }
+  return encodingParameters;
+};
+
+// parses http://draft.ortc.org/#rtcrtcpparameters*
+SDPUtils.parseRtcpParameters = function(mediaSection) {
+  const rtcpParameters = {};
+
+  // Gets the first SSRC. Note that with RTX there might be multiple
+  // SSRCs.
+  const remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+    .map(line => SDPUtils.parseSsrcMedia(line))
+    .filter(obj => obj.attribute === 'cname')[0];
+  if (remoteSsrc) {
+    rtcpParameters.cname = remoteSsrc.value;
+    rtcpParameters.ssrc = remoteSsrc.ssrc;
+  }
+
+  // Edge uses the compound attribute instead of reducedSize
+  // compound is !reducedSize
+  const rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
+  rtcpParameters.reducedSize = rsize.length > 0;
+  rtcpParameters.compound = rsize.length === 0;
+
+  // parses the rtcp-mux attrіbute.
+  // Note that Edge does not support unmuxed RTCP.
+  const mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
+  rtcpParameters.mux = mux.length > 0;
+
+  return rtcpParameters;
+};
+
+SDPUtils.writeRtcpParameters = function(rtcpParameters) {
+  let sdp = '';
+  if (rtcpParameters.reducedSize) {
+    sdp += 'a=rtcp-rsize\r\n';
+  }
+  if (rtcpParameters.mux) {
+    sdp += 'a=rtcp-mux\r\n';
+  }
+  if (rtcpParameters.ssrc !== undefined && rtcpParameters.cname) {
+    sdp += 'a=ssrc:' + rtcpParameters.ssrc +
+      ' cname:' + rtcpParameters.cname + '\r\n';
+  }
+  return sdp;
+};
+
+
+// parses either a=msid: or a=ssrc:... msid lines and returns
+// the id of the MediaStream and MediaStreamTrack.
+SDPUtils.parseMsid = function(mediaSection) {
+  let parts;
+  const spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
+  if (spec.length === 1) {
+    parts = spec[0].substring(7).split(' ');
+    return {stream: parts[0], track: parts[1]};
+  }
+  const planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+    .map(line => SDPUtils.parseSsrcMedia(line))
+    .filter(msidParts => msidParts.attribute === 'msid');
+  if (planB.length > 0) {
+    parts = planB[0].value.split(' ');
+    return {stream: parts[0], track: parts[1]};
+  }
+};
+
+// SCTP
+// parses draft-ietf-mmusic-sctp-sdp-26 first and falls back
+// to draft-ietf-mmusic-sctp-sdp-05
+SDPUtils.parseSctpDescription = function(mediaSection) {
+  const mline = SDPUtils.parseMLine(mediaSection);
+  const maxSizeLine = SDPUtils.matchPrefix(mediaSection, 'a=max-message-size:');
+  let maxMessageSize;
+  if (maxSizeLine.length > 0) {
+    maxMessageSize = parseInt(maxSizeLine[0].substring(19), 10);
+  }
+  if (isNaN(maxMessageSize)) {
+    maxMessageSize = 65536;
+  }
+  const sctpPort = SDPUtils.matchPrefix(mediaSection, 'a=sctp-port:');
+  if (sctpPort.length > 0) {
+    return {
+      port: parseInt(sctpPort[0].substring(12), 10),
+      protocol: mline.fmt,
+      maxMessageSize,
+    };
+  }
+  const sctpMapLines = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:');
+  if (sctpMapLines.length > 0) {
+    const parts = sctpMapLines[0]
+      .substring(10)
+      .split(' ');
+    return {
+      port: parseInt(parts[0], 10),
+      protocol: parts[1],
+      maxMessageSize,
+    };
+  }
+};
+
+// SCTP
+// outputs the draft-ietf-mmusic-sctp-sdp-26 version that all browsers
+// support by now receiving in this format, unless we originally parsed
+// as the draft-ietf-mmusic-sctp-sdp-05 format (indicated by the m-line
+// protocol of DTLS/SCTP -- without UDP/ or TCP/)
+SDPUtils.writeSctpDescription = function(media, sctp) {
+  let output = [];
+  if (media.protocol !== 'DTLS/SCTP') {
+    output = [
+      'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.protocol + '\r\n',
+      'c=IN IP4 0.0.0.0\r\n',
+      'a=sctp-port:' + sctp.port + '\r\n',
+    ];
+  } else {
+    output = [
+      'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.port + '\r\n',
+      'c=IN IP4 0.0.0.0\r\n',
+      'a=sctpmap:' + sctp.port + ' ' + sctp.protocol + ' 65535\r\n',
+    ];
+  }
+  if (sctp.maxMessageSize !== undefined) {
+    output.push('a=max-message-size:' + sctp.maxMessageSize + '\r\n');
+  }
+  return output.join('');
+};
+
+// Generate a session ID for SDP.
+// https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
+// recommends using a cryptographically random +ve 64-bit value
+// but right now this should be acceptable and within the right range
+SDPUtils.generateSessionId = function() {
+  return Math.random().toString().substr(2, 22);
+};
+
+// Write boiler plate for start of SDP
+// sessId argument is optional - if not supplied it will
+// be generated randomly
+// sessVersion is optional and defaults to 2
+// sessUser is optional and defaults to 'thisisadapterortc'
+SDPUtils.writeSessionBoilerplate = function(sessId, sessVer, sessUser) {
+  let sessionId;
+  const version = sessVer !== undefined ? sessVer : 2;
+  if (sessId) {
+    sessionId = sessId;
+  } else {
+    sessionId = SDPUtils.generateSessionId();
+  }
+  const user = sessUser || 'thisisadapterortc';
+  // FIXME: sess-id should be an NTP timestamp.
+  return 'v=0\r\n' +
+      'o=' + user + ' ' + sessionId + ' ' + version +
+        ' IN IP4 127.0.0.1\r\n' +
+      's=-\r\n' +
+      't=0 0\r\n';
+};
+
+// Gets the direction from the mediaSection or the sessionpart.
+SDPUtils.getDirection = function(mediaSection, sessionpart) {
+  // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
+  const lines = SDPUtils.splitLines(mediaSection);
+  for (let i = 0; i < lines.length; i++) {
+    switch (lines[i]) {
+      case 'a=sendrecv':
+      case 'a=sendonly':
+      case 'a=recvonly':
+      case 'a=inactive':
+        return lines[i].substring(2);
+      default:
+        // FIXME: What should happen here?
+    }
+  }
+  if (sessionpart) {
+    return SDPUtils.getDirection(sessionpart);
+  }
+  return 'sendrecv';
+};
+
+SDPUtils.getKind = function(mediaSection) {
+  const lines = SDPUtils.splitLines(mediaSection);
+  const mline = lines[0].split(' ');
+  return mline[0].substring(2);
+};
+
+SDPUtils.isRejected = function(mediaSection) {
+  return mediaSection.split(' ', 2)[1] === '0';
+};
+
+SDPUtils.parseMLine = function(mediaSection) {
+  const lines = SDPUtils.splitLines(mediaSection);
+  const parts = lines[0].substring(2).split(' ');
+  return {
+    kind: parts[0],
+    port: parseInt(parts[1], 10),
+    protocol: parts[2],
+    fmt: parts.slice(3).join(' '),
+  };
+};
+
+SDPUtils.parseOLine = function(mediaSection) {
+  const line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
+  const parts = line.substring(2).split(' ');
+  return {
+    username: parts[0],
+    sessionId: parts[1],
+    sessionVersion: parseInt(parts[2], 10),
+    netType: parts[3],
+    addressType: parts[4],
+    address: parts[5],
+  };
+};
+
+// a very naive interpretation of a valid SDP.
+SDPUtils.isValidSDP = function(blob) {
+  if (typeof blob !== 'string' || blob.length === 0) {
+    return false;
+  }
+  const lines = SDPUtils.splitLines(blob);
+  for (let i = 0; i < lines.length; i++) {
+    if (lines[i].length < 2 || lines[i].charAt(1) !== '=') {
+      return false;
+    }
+    // TODO: check the modifier a bit more.
+  }
+  return true;
+};
+
+// Expose public methods.
+if (typeof module === 'object') {
+  module.exports = SDPUtils;
+}