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copied!<p>Try <a href="https://webrtc-experiment.appspot.com/RTCMultiConnection/bandwidth/">this demo</a>. You can inject bandwidth attributes (<code>b=AS</code>) in the session descriptions:</p> <pre><code>audioBandwidth = 50; videoBandwidth = 256; function setBandwidth(sdp) { sdp = sdp.replace(/a=mid:audio\r\n/g, 'a=mid:audio\r\nb=AS:' + audioBandwidth + '\r\n'); sdp = sdp.replace(/a=mid:video\r\n/g, 'a=mid:video\r\nb=AS:' + videoBandwidth + '\r\n'); return sdp; } // ---------------------------------------------------------- peer.createOffer(function (sessionDescription) { sessionDescription.sdp = setBandwidth(sessionDescription.sdp); peer.setLocalDescription(sessionDescription); }, null, constraints); peer.createAnswer(function (sessionDescription) { sessionDescription.sdp = setBandwidth(sessionDescription.sdp); peer.setLocalDescription(sessionDescription); }, null, constraints); </code></pre> <p><code>b=AS</code> is already present in sdp for <code>data m-line</code>; its default value is <code>50</code>.</p> <h2>Updated at Sept 23, 2015</h2> <p><strong>Here is a library that provides full control over both audio/video tracks' bitrates:</strong></p> <pre><code>// here is how to use it var bandwidth = { screen: 300, // 300kbits minimum audio: 50, // 50kbits minimum video: 256 // 256kbits (both min-max) }; var isScreenSharing = false; sdp = BandwidthHandler.setApplicationSpecificBandwidth(sdp, bandwidth, isScreenSharing); sdp = BandwidthHandler.setVideoBitrates(sdp, { min: bandwidth.video, max: bandwidth.video }); sdp = BandwidthHandler.setOpusAttributes(sdp); </code></pre> <p><strong>Here is the library code. Its quite big but it works!</strong></p> <pre><code>// BandwidthHandler.js var BandwidthHandler = (function() { function setBAS(sdp, bandwidth, isScreen) { if (!!navigator.mozGetUserMedia || !bandwidth) { return sdp; } if (isScreen) { if (!bandwidth.screen) { console.warn('It seems that you are not using bandwidth for screen. Screen sharing is expected to fail.'); } else if (bandwidth.screen < 300) { console.warn('It seems that you are using wrong bandwidth value for screen. Screen sharing is expected to fail.'); } } // if screen; must use at least 300kbs if (bandwidth.screen && isScreen) { sdp = sdp.replace(/b=AS([^\r\n]+\r\n)/g, ''); sdp = sdp.replace(/a=mid:video\r\n/g, 'a=mid:video\r\nb=AS:' + bandwidth.screen + '\r\n'); } // remove existing bandwidth lines if (bandwidth.audio || bandwidth.video || bandwidth.data) { sdp = sdp.replace(/b=AS([^\r\n]+\r\n)/g, ''); } if (bandwidth.audio) { sdp = sdp.replace(/a=mid:audio\r\n/g, 'a=mid:audio\r\nb=AS:' + bandwidth.audio + '\r\n'); } if (bandwidth.video) { sdp = sdp.replace(/a=mid:video\r\n/g, 'a=mid:video\r\nb=AS:' + (isScreen ? bandwidth.screen : bandwidth.video) + '\r\n'); } return sdp; } // Find the line in sdpLines that starts with |prefix|, and, if specified, // contains |substr| (case-insensitive search). function findLine(sdpLines, prefix, substr) { return findLineInRange(sdpLines, 0, -1, prefix, substr); } // Find the line in sdpLines[startLine...endLine - 1] that starts with |prefix| // and, if specified, contains |substr| (case-insensitive search). function findLineInRange(sdpLines, startLine, endLine, prefix, substr) { var realEndLine = endLine !== -1 ? endLine : sdpLines.length; for (var i = startLine; i < realEndLine; ++i) { if (sdpLines[i].indexOf(prefix) === 0) { if (!substr || sdpLines[i].toLowerCase().indexOf(substr.toLowerCase()) !== -1) { return i; } } } return null; } // Gets the codec payload type from an a=rtpmap:X line. function getCodecPayloadType(sdpLine) { var pattern = new RegExp('a=rtpmap:(\\d+) \\w+\\/\\d+'); var result = sdpLine.match(pattern); return (result && result.length === 2) ? result[1] : null; } function setVideoBitrates(sdp, params) { params = params || {}; var xgoogle_min_bitrate = params.min; var xgoogle_max_bitrate = params.max; var sdpLines = sdp.split('\r\n'); // VP8 var vp8Index = findLine(sdpLines, 'a=rtpmap', 'VP8/90000'); var vp8Payload; if (vp8Index) { vp8Payload = getCodecPayloadType(sdpLines[vp8Index]); } if (!vp8Payload) { return sdp; } var rtxIndex = findLine(sdpLines, 'a=rtpmap', 'rtx/90000'); var rtxPayload; if (rtxIndex) { rtxPayload = getCodecPayloadType(sdpLines[rtxIndex]); } if (!rtxIndex) { return sdp; } var rtxFmtpLineIndex = findLine(sdpLines, 'a=fmtp:' + rtxPayload.toString()); if (rtxFmtpLineIndex !== null) { var appendrtxNext = '\r\n'; appendrtxNext += 'a=fmtp:' + vp8Payload + ' x-google-min-bitrate=' + (xgoogle_min_bitrate || '228') + '; x-google-max-bitrate=' + (xgoogle_max_bitrate || '228'); sdpLines[rtxFmtpLineIndex] = sdpLines[rtxFmtpLineIndex].concat(appendrtxNext); sdp = sdpLines.join('\r\n'); } return sdp; } function setOpusAttributes(sdp, params) { params = params || {}; var sdpLines = sdp.split('\r\n'); // Opus var opusIndex = findLine(sdpLines, 'a=rtpmap', 'opus/48000'); var opusPayload; if (opusIndex) { opusPayload = getCodecPayloadType(sdpLines[opusIndex]); } if (!opusPayload) { return sdp; } var opusFmtpLineIndex = findLine(sdpLines, 'a=fmtp:' + opusPayload.toString()); if (opusFmtpLineIndex === null) { return sdp; } var appendOpusNext = ''; appendOpusNext += '; stereo=' + (typeof params.stereo != 'undefined' ? params.stereo : '1'); appendOpusNext += '; sprop-stereo=' + (typeof params['sprop-stereo'] != 'undefined' ? params['sprop-stereo'] : '1'); if (typeof params.maxaveragebitrate != 'undefined') { appendOpusNext += '; maxaveragebitrate=' + (params.maxaveragebitrate || 128 * 1024 * 8); } if (typeof params.maxplaybackrate != 'undefined') { appendOpusNext += '; maxplaybackrate=' + (params.maxplaybackrate || 128 * 1024 * 8); } if (typeof params.cbr != 'undefined') { appendOpusNext += '; cbr=' + (typeof params.cbr != 'undefined' ? params.cbr : '1'); } if (typeof params.useinbandfec != 'undefined') { appendOpusNext += '; useinbandfec=' + params.useinbandfec; } if (typeof params.usedtx != 'undefined') { appendOpusNext += '; usedtx=' + params.usedtx; } if (typeof params.maxptime != 'undefined') { appendOpusNext += '\r\na=maxptime:' + params.maxptime; } sdpLines[opusFmtpLineIndex] = sdpLines[opusFmtpLineIndex].concat(appendOpusNext); sdp = sdpLines.join('\r\n'); return sdp; } return { setApplicationSpecificBandwidth: function(sdp, bandwidth, isScreen) { return setBAS(sdp, bandwidth, isScreen); }, setVideoBitrates: function(sdp, params) { return setVideoBitrates(sdp, params); }, setOpusAttributes: function(sdp, params) { return setOpusAttributes(sdp, params); } }; })(); </code></pre> <p><strong>Here is how to set advance opus bitrate parameters:</strong></p> <pre><code>sdp = BandwidthHandler.setOpusAttributes(sdp, { 'stereo': 0, // to disable stereo (to force mono audio) 'sprop-stereo': 1, 'maxaveragebitrate': 500 * 1024 * 8, // 500 kbits 'maxplaybackrate': 500 * 1024 * 8, // 500 kbits 'cbr': 0, // disable cbr 'useinbandfec': 1, // use inband fec 'usedtx': 1, // use dtx 'maxptime': 3 }); </code></pre>

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