synapse/contrib/jitsimeetbridge/unjingle/strophe.jingle.sdp.js

/* jshint -W117 */
// SDP STUFF
function SDP(sdp) {
    this.media = sdp.split('\r\nm=');
    for (var i = 1; i < this.media.length; i++) {
        this.media[i] = 'm=' + this.media[i];
        if (i != this.media.length - 1) {
            this.media[i] += '\r\n';
        }
    }
    this.session = this.media.shift() + '\r\n';
    this.raw = this.session + this.media.join('');
}

exports.SDP = SDP;

var jsdom          = require("jsdom");
var window = jsdom.jsdom().parentWindow;
var $ = require('jquery')(window);

var SDPUtil = require('./strophe.jingle.sdp.util.js').SDPUtil;

/**
 * Returns map of MediaChannel mapped per channel idx.
 */
SDP.prototype.getMediaSsrcMap = function() {
    var self = this;
    var media_ssrcs = {};
    for (channelNum = 0; channelNum < self.media.length; channelNum++) {
        modified = true;
        tmp = SDPUtil.find_lines(self.media[channelNum], 'a=ssrc:');
        var type = SDPUtil.parse_mid(SDPUtil.find_line(self.media[channelNum], 'a=mid:'));
        var channel = new MediaChannel(channelNum, type);
        media_ssrcs[channelNum] = channel;
        tmp.forEach(function (line) {
            var linessrc = line.substring(7).split(' ')[0];
            // allocate new ChannelSsrc
            if(!channel.ssrcs[linessrc]) {
                channel.ssrcs[linessrc] = new ChannelSsrc(linessrc, type);
            }
            channel.ssrcs[linessrc].lines.push(line);
        });
        tmp = SDPUtil.find_lines(self.media[channelNum], 'a=ssrc-group:');
        tmp.forEach(function(line){
            var semantics = line.substr(0, idx).substr(13);
            var ssrcs = line.substr(14 + semantics.length).split(' ');
            if (ssrcs.length != 0) {
                var ssrcGroup = new ChannelSsrcGroup(semantics, ssrcs);
                channel.ssrcGroups.push(ssrcGroup);
            }
        });
    }
    return media_ssrcs;
};
/**
 * Returns <tt>true</tt> if this SDP contains given SSRC.
 * @param ssrc the ssrc to check.
 * @returns {boolean} <tt>true</tt> if this SDP contains given SSRC.
 */
SDP.prototype.containsSSRC = function(ssrc) {
    var channels = this.getMediaSsrcMap();
    var contains = false;
    Object.keys(channels).forEach(function(chNumber){
        var channel = channels[chNumber];
        //console.log("Check", channel, ssrc);
        if(Object.keys(channel.ssrcs).indexOf(ssrc) != -1){
            contains = true;
        }
    });
    return contains;
};

/**
 * Returns map of MediaChannel that contains only media not contained in <tt>otherSdp</tt>. Mapped by channel idx.
 * @param otherSdp the other SDP to check ssrc with.
 */
SDP.prototype.getNewMedia = function(otherSdp) {

    // this could be useful in Array.prototype.
    function arrayEquals(array) {
        // if the other array is a falsy value, return
        if (!array)
            return false;

        // compare lengths - can save a lot of time
        if (this.length != array.length)
            return false;

        for (var i = 0, l=this.length; i < l; i++) {
            // Check if we have nested arrays
            if (this[i] instanceof Array && array[i] instanceof Array) {
                // recurse into the nested arrays
                if (!this[i].equals(array[i]))
                    return false;
            }
            else if (this[i] != array[i]) {
                // Warning - two different object instances will never be equal: {x:20} != {x:20}
                return false;
            }
        }
        return true;
    }

    var myMedia = this.getMediaSsrcMap();
    var othersMedia = otherSdp.getMediaSsrcMap();
    var newMedia = {};
    Object.keys(othersMedia).forEach(function(channelNum) {
        var myChannel = myMedia[channelNum];
        var othersChannel = othersMedia[channelNum];
        if(!myChannel && othersChannel) {
            // Add whole channel
            newMedia[channelNum] = othersChannel;
            return;
        }
        // Look for new ssrcs accross the channel
        Object.keys(othersChannel.ssrcs).forEach(function(ssrc) {
            if(Object.keys(myChannel.ssrcs).indexOf(ssrc) === -1) {
                // Allocate channel if we've found ssrc that doesn't exist in our channel
                if(!newMedia[channelNum]){
                    newMedia[channelNum] = new MediaChannel(othersChannel.chNumber, othersChannel.mediaType);
                }
                newMedia[channelNum].ssrcs[ssrc] = othersChannel.ssrcs[ssrc];
            }
        });

        // Look for new ssrc groups across the channels
        othersChannel.ssrcGroups.forEach(function(otherSsrcGroup){

            // try to match the other ssrc-group with an ssrc-group of ours
            var matched = false;
            for (var i = 0; i < myChannel.ssrcGroups.length; i++) {
                var mySsrcGroup = myChannel.ssrcGroups[i];
                if (otherSsrcGroup.semantics == mySsrcGroup.semantics
                    && arrayEquals.apply(otherSsrcGroup.ssrcs, [mySsrcGroup.ssrcs])) {

                    matched = true;
                    break;
                }
            }

            if (!matched) {
                // Allocate channel if we've found an ssrc-group that doesn't
                // exist in our channel

                if(!newMedia[channelNum]){
                    newMedia[channelNum] = new MediaChannel(othersChannel.chNumber, othersChannel.mediaType);
                }
                newMedia[channelNum].ssrcGroups.push(otherSsrcGroup);
            }
        });
    });
    return newMedia;
};

// remove iSAC and CN from SDP
SDP.prototype.mangle = function () {
    var i, j, mline, lines, rtpmap, newdesc;
    for (i = 0; i < this.media.length; i++) {
        lines = this.media[i].split('\r\n');
        lines.pop(); // remove empty last element
        mline = SDPUtil.parse_mline(lines.shift());
        if (mline.media != 'audio')
            continue;
        newdesc = '';
        mline.fmt.length = 0;
        for (j = 0; j < lines.length; j++) {
            if (lines[j].substr(0, 9) == 'a=rtpmap:') {
                rtpmap = SDPUtil.parse_rtpmap(lines[j]);
                if (rtpmap.name == 'CN' || rtpmap.name == 'ISAC')
                    continue;
                mline.fmt.push(rtpmap.id);
                newdesc += lines[j] + '\r\n';
            } else {
                newdesc += lines[j] + '\r\n';
            }
        }
        this.media[i] = SDPUtil.build_mline(mline) + '\r\n';
        this.media[i] += newdesc;
    }
    this.raw = this.session + this.media.join('');
};

// remove lines matching prefix from session section
SDP.prototype.removeSessionLines = function(prefix) {
    var self = this;
    var lines = SDPUtil.find_lines(this.session, prefix);
    lines.forEach(function(line) {
        self.session = self.session.replace(line + '\r\n', '');
    });
    this.raw = this.session + this.media.join('');
    return lines;
}
// remove lines matching prefix from a media section specified by mediaindex
// TODO: non-numeric mediaindex could match mid
SDP.prototype.removeMediaLines = function(mediaindex, prefix) {
    var self = this;
    var lines = SDPUtil.find_lines(this.media[mediaindex], prefix);
    lines.forEach(function(line) {
        self.media[mediaindex] = self.media[mediaindex].replace(line + '\r\n', '');
    });
    this.raw = this.session + this.media.join('');
    return lines;
}

// add content's to a jingle element
SDP.prototype.toJingle = function (elem, thecreator) {
    var i, j, k, mline, ssrc, rtpmap, tmp, line, lines;
    var self = this;
    // new bundle plan
    if (SDPUtil.find_line(this.session, 'a=group:')) {
        lines = SDPUtil.find_lines(this.session, 'a=group:');
        for (i = 0; i < lines.length; i++) {
            tmp = lines[i].split(' ');
            var semantics = tmp.shift().substr(8);
            elem.c('group', {xmlns: 'urn:xmpp:jingle:apps:grouping:0', semantics:semantics});
            for (j = 0; j < tmp.length; j++) {
                elem.c('content', {name: tmp[j]}).up();
            }
            elem.up();
        }
    }
    // old bundle plan, to be removed
    var bundle = [];
    if (SDPUtil.find_line(this.session, 'a=group:BUNDLE')) {
        bundle = SDPUtil.find_line(this.session, 'a=group:BUNDLE ').split(' ');
        bundle.shift();
    }
    for (i = 0; i < this.media.length; i++) {
        mline = SDPUtil.parse_mline(this.media[i].split('\r\n')[0]);
        if (!(mline.media === 'audio' ||
              mline.media === 'video' ||
              mline.media === 'application'))
        {
            continue;
        }
        if (SDPUtil.find_line(this.media[i], 'a=ssrc:')) {
            ssrc = SDPUtil.find_line(this.media[i], 'a=ssrc:').substring(7).split(' ')[0]; // take the first
        } else {
            ssrc = false;
        }

        elem.c('content', {creator: thecreator, name: mline.media});
        if (SDPUtil.find_line(this.media[i], 'a=mid:')) {
            // prefer identifier from a=mid if present
            var mid = SDPUtil.parse_mid(SDPUtil.find_line(this.media[i], 'a=mid:'));
            elem.attrs({ name: mid });

            // old BUNDLE plan, to be removed
            if (bundle.indexOf(mid) !== -1) {
                elem.c('bundle', {xmlns: 'http://estos.de/ns/bundle'}).up();
                bundle.splice(bundle.indexOf(mid), 1);
            }
        }

        if (SDPUtil.find_line(this.media[i], 'a=rtpmap:').length)
        {
            elem.c('description',
                {xmlns: 'urn:xmpp:jingle:apps:rtp:1',
                    media: mline.media });
            if (ssrc) {
                elem.attrs({ssrc: ssrc});
            }
            for (j = 0; j < mline.fmt.length; j++) {
                rtpmap = SDPUtil.find_line(this.media[i], 'a=rtpmap:' + mline.fmt[j]);
                elem.c('payload-type', SDPUtil.parse_rtpmap(rtpmap));
                // put any 'a=fmtp:' + mline.fmt[j] lines into <param name=foo value=bar/>
                if (SDPUtil.find_line(this.media[i], 'a=fmtp:' + mline.fmt[j])) {
                    tmp = SDPUtil.parse_fmtp(SDPUtil.find_line(this.media[i], 'a=fmtp:' + mline.fmt[j]));
                    for (k = 0; k < tmp.length; k++) {
                        elem.c('parameter', tmp[k]).up();
                    }
                }
                this.RtcpFbToJingle(i, elem, mline.fmt[j]); // XEP-0293 -- map a=rtcp-fb

                elem.up();
            }
            if (SDPUtil.find_line(this.media[i], 'a=crypto:', this.session)) {
                elem.c('encryption', {required: 1});
                var crypto = SDPUtil.find_lines(this.media[i], 'a=crypto:', this.session);
                crypto.forEach(function(line) {
                    elem.c('crypto', SDPUtil.parse_crypto(line)).up();
                });
                elem.up(); // end of encryption
            }

            if (ssrc) {
                // new style mapping
                elem.c('source', { ssrc: ssrc, xmlns: 'urn:xmpp:jingle:apps:rtp:ssma:0' });
                // FIXME: group by ssrc and support multiple different ssrcs
                var ssrclines = SDPUtil.find_lines(this.media[i], 'a=ssrc:');
                ssrclines.forEach(function(line) {
                    idx = line.indexOf(' ');
                    var linessrc = line.substr(0, idx).substr(7);
                    if (linessrc != ssrc) {
                        elem.up();
                        ssrc = linessrc;
                        elem.c('source', { ssrc: ssrc, xmlns: 'urn:xmpp:jingle:apps:rtp:ssma:0' });
                    }
                    var kv = line.substr(idx + 1);
                    elem.c('parameter');
                    if (kv.indexOf(':') == -1) {
                        elem.attrs({ name: kv });
                    } else {
                        elem.attrs({ name: kv.split(':', 2)[0] });
                        elem.attrs({ value: kv.split(':', 2)[1] });
                    }
                    elem.up();
                });
                elem.up();

                // old proprietary mapping, to be removed at some point
                tmp = SDPUtil.parse_ssrc(this.media[i]);
                tmp.xmlns = 'http://estos.de/ns/ssrc';
                tmp.ssrc = ssrc;
                elem.c('ssrc', tmp).up(); // ssrc is part of description

                // XEP-0339 handle ssrc-group attributes
                var ssrc_group_lines = SDPUtil.find_lines(this.media[i], 'a=ssrc-group:');
                ssrc_group_lines.forEach(function(line) {
                    idx = line.indexOf(' ');
                    var semantics = line.substr(0, idx).substr(13);
                    var ssrcs = line.substr(14 + semantics.length).split(' ');
                    if (ssrcs.length != 0) {
                        elem.c('ssrc-group', { semantics: semantics, xmlns: 'urn:xmpp:jingle:apps:rtp:ssma:0' });
                        ssrcs.forEach(function(ssrc) {
                            elem.c('source', { ssrc: ssrc })
                                .up();
                        });
                        elem.up();
                    }
                });
            }

            if (SDPUtil.find_line(this.media[i], 'a=rtcp-mux')) {
                elem.c('rtcp-mux').up();
            }

            // XEP-0293 -- map a=rtcp-fb:*
            this.RtcpFbToJingle(i, elem, '*');

            // XEP-0294
            if (SDPUtil.find_line(this.media[i], 'a=extmap:')) {
                lines = SDPUtil.find_lines(this.media[i], 'a=extmap:');
                for (j = 0; j < lines.length; j++) {
                    tmp = SDPUtil.parse_extmap(lines[j]);
                    elem.c('rtp-hdrext', { xmlns: 'urn:xmpp:jingle:apps:rtp:rtp-hdrext:0',
                        uri: tmp.uri,
                        id: tmp.value });
                    if (tmp.hasOwnProperty('direction')) {
                        switch (tmp.direction) {
                            case 'sendonly':
                                elem.attrs({senders: 'responder'});
                                break;
                            case 'recvonly':
                                elem.attrs({senders: 'initiator'});
                                break;
                            case 'sendrecv':
                                elem.attrs({senders: 'both'});
                                break;
                            case 'inactive':
                                elem.attrs({senders: 'none'});
                                break;
                        }
                    }
                    // TODO: handle params
                    elem.up();
                }
            }
            elem.up(); // end of description
        }

        // map ice-ufrag/pwd, dtls fingerprint, candidates
        this.TransportToJingle(i, elem);

        if (SDPUtil.find_line(this.media[i], 'a=sendrecv', this.session)) {
            elem.attrs({senders: 'both'});
        } else if (SDPUtil.find_line(this.media[i], 'a=sendonly', this.session)) {
            elem.attrs({senders: 'initiator'});
        } else if (SDPUtil.find_line(this.media[i], 'a=recvonly', this.session)) {
            elem.attrs({senders: 'responder'});
        } else if (SDPUtil.find_line(this.media[i], 'a=inactive', this.session)) {
            elem.attrs({senders: 'none'});
        }
        if (mline.port == '0') {
            // estos hack to reject an m-line
            elem.attrs({senders: 'rejected'});
        }
        elem.up(); // end of content
    }
    elem.up();
    return elem;
};

SDP.prototype.TransportToJingle = function (mediaindex, elem) {
    var i = mediaindex;
    var tmp;
    var self = this;
    elem.c('transport');

    // XEP-0343 DTLS/SCTP
    if (SDPUtil.find_line(this.media[mediaindex], 'a=sctpmap:').length)
    {
        var sctpmap = SDPUtil.find_line(
            this.media[i], 'a=sctpmap:', self.session);
        if (sctpmap)
        {
            var sctpAttrs = SDPUtil.parse_sctpmap(sctpmap);
            elem.c('sctpmap',
                {
                    xmlns: 'urn:xmpp:jingle:transports:dtls-sctp:1',
                    number: sctpAttrs[0], /* SCTP port */
                    protocol: sctpAttrs[1], /* protocol */
                });
            // Optional stream count attribute
            if (sctpAttrs.length > 2)
                elem.attrs({ streams: sctpAttrs[2]});
            elem.up();
        }
    }
    // XEP-0320
    var fingerprints = SDPUtil.find_lines(this.media[mediaindex], 'a=fingerprint:', this.session);
    fingerprints.forEach(function(line) {
        tmp = SDPUtil.parse_fingerprint(line);
        tmp.xmlns = 'urn:xmpp:jingle:apps:dtls:0';
        elem.c('fingerprint').t(tmp.fingerprint);
        delete tmp.fingerprint;
        line = SDPUtil.find_line(self.media[mediaindex], 'a=setup:', self.session);
        if (line) {
            tmp.setup = line.substr(8);
        }
        elem.attrs(tmp);
        elem.up(); // end of fingerprint
    });
    tmp = SDPUtil.iceparams(this.media[mediaindex], this.session);
    if (tmp) {
        tmp.xmlns = 'urn:xmpp:jingle:transports:ice-udp:1';
        elem.attrs(tmp);
        // XEP-0176
        if (SDPUtil.find_line(this.media[mediaindex], 'a=candidate:', this.session)) { // add any a=candidate lines
            var lines = SDPUtil.find_lines(this.media[mediaindex], 'a=candidate:', this.session);
            lines.forEach(function (line) {
                elem.c('candidate', SDPUtil.candidateToJingle(line)).up();
            });
        }
    }
    elem.up(); // end of transport
}

SDP.prototype.RtcpFbToJingle = function (mediaindex, elem, payloadtype) { // XEP-0293
    var lines = SDPUtil.find_lines(this.media[mediaindex], 'a=rtcp-fb:' + payloadtype);
    lines.forEach(function (line) {
        var tmp = SDPUtil.parse_rtcpfb(line);
        if (tmp.type == 'trr-int') {
            elem.c('rtcp-fb-trr-int', {xmlns: 'urn:xmpp:jingle:apps:rtp:rtcp-fb:0', value: tmp.params[0]});
            elem.up();
        } else {
            elem.c('rtcp-fb', {xmlns: 'urn:xmpp:jingle:apps:rtp:rtcp-fb:0', type: tmp.type});
            if (tmp.params.length > 0) {
                elem.attrs({'subtype': tmp.params[0]});
            }
            elem.up();
        }
    });
};

SDP.prototype.RtcpFbFromJingle = function (elem, payloadtype) { // XEP-0293
    var media = '';
    var tmp = elem.find('>rtcp-fb-trr-int[xmlns="urn:xmpp:jingle:apps:rtp:rtcp-fb:0"]');
    if (tmp.length) {
        media += 'a=rtcp-fb:' + '*' + ' ' + 'trr-int' + ' ';
        if (tmp.attr('value')) {
            media += tmp.attr('value');
        } else {
            media += '0';
        }
        media += '\r\n';
    }
    tmp = elem.find('>rtcp-fb[xmlns="urn:xmpp:jingle:apps:rtp:rtcp-fb:0"]');
    tmp.each(function () {
        media += 'a=rtcp-fb:' + payloadtype + ' ' + $(this).attr('type');
        if ($(this).attr('subtype')) {
            media += ' ' + $(this).attr('subtype');
        }
        media += '\r\n';
    });
    return media;
};

// construct an SDP from a jingle stanza
SDP.prototype.fromJingle = function (jingle) {
    var self = this;
    this.raw = 'v=0\r\n' +
        'o=- ' + '1923518516' + ' 2 IN IP4 0.0.0.0\r\n' +// FIXME
        's=-\r\n' +
        't=0 0\r\n';
    // http://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-04#section-8
    if ($(jingle).find('>group[xmlns="urn:xmpp:jingle:apps:grouping:0"]').length) {
        $(jingle).find('>group[xmlns="urn:xmpp:jingle:apps:grouping:0"]').each(function (idx, group) {
            var contents = $(group).find('>content').map(function (idx, content) {
                return content.getAttribute('name');
            }).get();
            if (contents.length > 0) {
                self.raw += 'a=group:' + (group.getAttribute('semantics') || group.getAttribute('type')) + ' ' + contents.join(' ') + '\r\n';
            }
        });
    } else if ($(jingle).find('>group[xmlns="urn:ietf:rfc:5888"]').length) {
        // temporary namespace, not to be used. to be removed soon.
        $(jingle).find('>group[xmlns="urn:ietf:rfc:5888"]').each(function (idx, group) {
            var contents = $(group).find('>content').map(function (idx, content) {
                return content.getAttribute('name');
            }).get();
            if (group.getAttribute('type') !== null && contents.length > 0) {
                self.raw += 'a=group:' + group.getAttribute('type') + ' ' + contents.join(' ') + '\r\n';
            }
        });
    } else {
        // for backward compability, to be removed soon
        // assume all contents are in the same bundle group, can be improved upon later
        var bundle = $(jingle).find('>content').filter(function (idx, content) {
            //elem.c('bundle', {xmlns:'http://estos.de/ns/bundle'});
            return $(content).find('>bundle').length > 0;
        }).map(function (idx, content) {
                return content.getAttribute('name');
            }).get();
        if (bundle.length) {
            this.raw += 'a=group:BUNDLE ' + bundle.join(' ') + '\r\n';
        }
    }

    this.session = this.raw;
    jingle.find('>content').each(function () {
        var m = self.jingle2media($(this));
        self.media.push(m);
    });

    // reconstruct msid-semantic -- apparently not necessary
    /*
     var msid = SDPUtil.parse_ssrc(this.raw);
     if (msid.hasOwnProperty('mslabel')) {
     this.session += "a=msid-semantic: WMS " + msid.mslabel + "\r\n";
     }
     */

    this.raw = this.session + this.media.join('');
};

// translate a jingle content element into an an SDP media part
SDP.prototype.jingle2media = function (content) {
    var media = '',
        desc = content.find('description'),
        ssrc = desc.attr('ssrc'),
        self = this,
        tmp;
    var sctp = content.find(
        '>transport>sctpmap[xmlns="urn:xmpp:jingle:transports:dtls-sctp:1"]');

    tmp = { media: desc.attr('media') };
    tmp.port = '1';
    if (content.attr('senders') == 'rejected') {
        // estos hack to reject an m-line.
        tmp.port = '0';
    }
    if (content.find('>transport>fingerprint').length || desc.find('encryption').length) {
        if (sctp.length)
            tmp.proto = 'DTLS/SCTP';
        else
            tmp.proto = 'RTP/SAVPF';
    } else {
        tmp.proto = 'RTP/AVPF';
    }
    if (!sctp.length)
    {
        tmp.fmt = desc.find('payload-type').map(
            function () { return this.getAttribute('id'); }).get();
        media += SDPUtil.build_mline(tmp) + '\r\n';
    }
    else
    {
        media += 'm=application 1 DTLS/SCTP ' + sctp.attr('number') + '\r\n';
        media += 'a=sctpmap:' + sctp.attr('number') +
            ' ' + sctp.attr('protocol');

        var streamCount = sctp.attr('streams');
        if (streamCount)
            media += ' ' + streamCount + '\r\n';
        else
            media += '\r\n';
    }

    media += 'c=IN IP4 0.0.0.0\r\n';
    if (!sctp.length)
        media += 'a=rtcp:1 IN IP4 0.0.0.0\r\n';
    //tmp = content.find('>transport[xmlns="urn:xmpp:jingle:transports:ice-udp:1"]');
    tmp = content.find('>bundle>transport[xmlns="urn:xmpp:jingle:transports:ice-udp:1"]');
    //console.log('transports: '+content.find('>transport[xmlns="urn:xmpp:jingle:transports:ice-udp:1"]').length);
    //console.log('bundle.transports: '+content.find('>bundle>transport[xmlns="urn:xmpp:jingle:transports:ice-udp:1"]').length);
    //console.log("tmp fingerprint: "+tmp.find('>fingerprint').innerHTML);
    if (tmp.length) {
        if (tmp.attr('ufrag')) {
            media += SDPUtil.build_iceufrag(tmp.attr('ufrag')) + '\r\n';
        }
        if (tmp.attr('pwd')) {
            media += SDPUtil.build_icepwd(tmp.attr('pwd')) + '\r\n';
        }
        tmp.find('>fingerprint').each(function () {
            // FIXME: check namespace at some point
            media += 'a=fingerprint:' + this.getAttribute('hash');
            media += ' ' + $(this).text();
            media += '\r\n';
            //console.log("mline "+media);
            if (this.getAttribute('setup')) {
                media += 'a=setup:' + this.getAttribute('setup') + '\r\n';
            }
        });
    }
    switch (content.attr('senders')) {
        case 'initiator':
            media += 'a=sendonly\r\n';
            break;
        case 'responder':
            media += 'a=recvonly\r\n';
            break;
        case 'none':
            media += 'a=inactive\r\n';
            break;
        case 'both':
            media += 'a=sendrecv\r\n';
            break;
    }
    media += 'a=mid:' + content.attr('name') + '\r\n';
    /*if (content.attr('name') == 'video') {
        media += 'a=x-google-flag:conference' + '\r\n';
    }*/

    // <description><rtcp-mux/></description>
    // see http://code.google.com/p/libjingle/issues/detail?id=309 -- no spec though
    // and http://mail.jabber.org/pipermail/jingle/2011-December/001761.html
    if (desc.find('rtcp-mux').length) {
        media += 'a=rtcp-mux\r\n';
    }

    if (desc.find('encryption').length) {
        desc.find('encryption>crypto').each(function () {
            media += 'a=crypto:' + this.getAttribute('tag');
            media += ' ' + this.getAttribute('crypto-suite');
            media += ' ' + this.getAttribute('key-params');
            if (this.getAttribute('session-params')) {
                media += ' ' + this.getAttribute('session-params');
            }
            media += '\r\n';
        });
    }
    desc.find('payload-type').each(function () {
        media += SDPUtil.build_rtpmap(this) + '\r\n';
        if ($(this).find('>parameter').length) {
            media += 'a=fmtp:' + this.getAttribute('id') + ' ';
            media += $(this).find('parameter').map(function () { return (this.getAttribute('name') ? (this.getAttribute('name') + '=') : '') + this.getAttribute('value'); }).get().join('; ');
            media += '\r\n';
        }
        // xep-0293
        media += self.RtcpFbFromJingle($(this), this.getAttribute('id'));
    });

    // xep-0293
    media += self.RtcpFbFromJingle(desc, '*');

    // xep-0294
    tmp = desc.find('>rtp-hdrext[xmlns="urn:xmpp:jingle:apps:rtp:rtp-hdrext:0"]');
    tmp.each(function () {
        media += 'a=extmap:' + this.getAttribute('id') + ' ' + this.getAttribute('uri') + '\r\n';
    });

    content.find('>bundle>transport[xmlns="urn:xmpp:jingle:transports:ice-udp:1"]>candidate').each(function () {
        media += SDPUtil.candidateFromJingle(this);
    });

    // XEP-0339 handle ssrc-group attributes
    tmp = content.find('description>ssrc-group[xmlns="urn:xmpp:jingle:apps:rtp:ssma:0"]').each(function() {
        var semantics = this.getAttribute('semantics');
        var ssrcs = $(this).find('>source').map(function() {
            return this.getAttribute('ssrc');
        }).get();

        if (ssrcs.length != 0) {
            media += 'a=ssrc-group:' + semantics + ' ' + ssrcs.join(' ') + '\r\n';
        }
    });

    tmp = content.find('description>source[xmlns="urn:xmpp:jingle:apps:rtp:ssma:0"]');
    tmp.each(function () {
        var ssrc = this.getAttribute('ssrc');
        $(this).find('>parameter').each(function () {
            media += 'a=ssrc:' + ssrc + ' ' + this.getAttribute('name');
            if (this.getAttribute('value') && this.getAttribute('value').length)
                media += ':' + this.getAttribute('value');
            media += '\r\n';
        });
    });

    if (tmp.length === 0) {
        // fallback to proprietary mapping of a=ssrc lines
        tmp = content.find('description>ssrc[xmlns="http://estos.de/ns/ssrc"]');
        if (tmp.length) {
            media += 'a=ssrc:' + ssrc + ' cname:' + tmp.attr('cname') + '\r\n';
            media += 'a=ssrc:' + ssrc + ' msid:' + tmp.attr('msid') + '\r\n';
            media += 'a=ssrc:' + ssrc + ' mslabel:' + tmp.attr('mslabel') + '\r\n';
            media += 'a=ssrc:' + ssrc + ' label:' + tmp.attr('label') + '\r\n';
        }
    }
    return media;
};