code: function getMLinePayloadTypes (mediaLine, mediaType) {
        var mLineSelector = new RegExp('^m=' + mediaType +
                              ' \\d+(/\\d+)? [a-zA-Z0-9/]+(( [a-zA-Z0-9/]+)+)$', 'i');
  
        // Get all payload types that the line supports
        var payloadTypes = mediaLine.match(mLineSelector);
        if (!payloadTypes || payloadTypes.length < 2) {
          // Error, invalid M line?
          return [];
        }
  
        return OT.$.trim(payloadTypes[2]).split(' ');
      }
docs: Extract the payload types for a give Media Line.