spreed-webrtc/static/js/mediastream/utils.js

/*
 * Spreed WebRTC.
 * Copyright (C) 2013-2014 struktur AG
 *
 * This file is part of Spreed WebRTC.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
define([], function() {

	var Utils = function() {}

	Utils.prototype.mergeConstraints = function(cons1, cons2) {
		var merged = cons1;
		var name;
		for (name in cons2.mandatory) {
			if (cons2.mandatory.hasOwnProperty(name)) {
				merged.mandatory[name] = cons2.mandatory[name];
			}
		}
		merged.optional.concat(cons2.optional);
		return merged;
	};

	Utils.prototype.extractSdp = function(sdpLine, pattern) {
		var result = sdpLine.match(pattern);
		return (result && result.length == 2) ? result[1] : null;
	};

	Utils.prototype.addStereo = function(sdp) {
		// Set Opus in Stereo.

		var sdpLines = sdp.split('\r\n');
		var opusPayload = "";
		var fmtpLineIndex = null;
		var i;

		// Find opus payload.
		for (i = 0; i < sdpLines.length; i++) {
			if (sdpLines[i].search('opus/48000') !== -1) {
				opusPayload = this.extractSdp(sdpLines[i], /:(\d+) opus\/48000/i);
				break;
			}
		}

		// Find the payload in fmtp line.
		for (i = 0; i < sdpLines.length; i++) {
			if (sdpLines[i].search('a=fmtp') !== -1) {
				var payload = this.extractSdp(sdpLines[i], /a=fmtp:(\d+)/);
				if (payload === opusPayload) {
					fmtpLineIndex = i;
					break;
				}
			}
		}
		// No fmtp line found.
		if (fmtpLineIndex === null) {
			console.log("Unable to add stereo (no fmtp line for opus payload)", opusPayload);
			return sdp;
		}

		// Append stereo=1 to fmtp line.
		sdpLines[fmtpLineIndex] = sdpLines[fmtpLineIndex].concat(' stereo=1');

		sdp = sdpLines.join('\r\n');
		console.log("Enabled opus stereo.");
		return sdp;

	};

	Utils.prototype.preferOpus = function(sdp) {
		// Set Opus as the preferred codec in SDP if Opus is present.

		var sdpLines = sdp.split('\r\n');
		var mLineIndex = null;
		var i;

		// Search for m line.
		for (i = 0; i < sdpLines.length; i++) {
			if (sdpLines[i].search('m=audio') !== -1) {
				mLineIndex = i;
				break;
			}
		}
		if (mLineIndex === null) {
			return sdp;
		}

		// If Opus is available, set it as the default in m line.
		for (i = 0; i < sdpLines.length; i++) {
			if (sdpLines[i].search('opus/48000') !== -1) {
				var opusPayload = this.extractSdp(sdpLines[i], /:(\d+) opus\/48000/i);
				if (opusPayload) {
					sdpLines[mLineIndex] = this.setDefaultCodec(sdpLines[mLineIndex], opusPayload);
				}
				break;
			}
		}

		// Remove CN in m line and sdp.
		sdpLines = this.removeCN(sdpLines, mLineIndex);

		sdp = sdpLines.join('\r\n');
		return sdp;

	};

	Utils.prototype.setDefaultCodec = function(mLine, payload) {
		// Set the selected codec to the first in m line.
		var elements = mLine.split(' ');
		var newLine = [];
		var index = 0;
		for (var i = 0; i < elements.length; i++) {
			// Format of media starts from the fourth.
			if (index === 3) {
				newLine[index++] = payload; // Put target payload to the first.
			}
			if (elements[i] !== payload) {
				newLine[index++] = elements[i];
			}
		}
		return newLine.join(' ');
	};

	Utils.prototype.removeCN = function(sdpLines, mLineIndex) {
		// Strip CN from sdp before CN constraints is ready.
		var mLineElements = sdpLines[mLineIndex].split(' ');
		// Scan from end for the convenience of removing an item.
		for (var i = sdpLines.length - 1; i >= 0; i--) {
			var payload = this.extractSdp(sdpLines[i], /a=rtpmap:(\d+) CN\/\d+/i);
			if (payload) {
				var cnPos = mLineElements.indexOf(payload);
				if (cnPos !== -1) {
					// Remove CN payload from m line.
					mLineElements.splice(cnPos, 1);
				}
				// Remove CN line in sdp
				sdpLines.splice(i, 1);
			}
		}
		sdpLines[mLineIndex] = mLineElements.join(' ');
		return sdpLines;
	};

	var utils = new Utils();
	return utils;

});