How to control bandwidth in WebRTC video call?

Question

I am trying to develop a Video Calling/Conferencing application using WebRTC and node.js. Right now there is no facility to control bandwidth during during video call. Is there any way to control/reduce bandwidth. (like I want make whole my web application to work on 150 kbps while video conferencing).

Any suggestions are highly appreciated. Thanks in advance.

Answer 1

Try this demo. You can inject bandwidth attributes (b=AS) in the session descriptions:

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); 

b=AS is already present in sdp for data m-line; its default value is 50.

Updated at Sept 23, 2015

Here is a library that provides full control over both audio/video tracks' bitrates:

// 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); 

Here is the library code. Its quite big but it works!

// 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);         }     }; })(); 

Here is how to set advance opus bitrate parameters:

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 }); 

Answer 2

A more up-to-date answer

const videobitrate = 20000; var offer = pc.localDescription; // Set bandwidth for video offer.sdp = offer.sdp.replace(/(m=video.*\r\n)/g, `$1b=AS:${videobitrate}\r\n`); pc.setLocalDescription(offer); 

Explanation: a=mid:video is not a guaranteed tag. For receive only video, you might not see it or see a=mid:0. Generally it's a better bet to look for the m=video xxxx xxxx (or similar audio) tag and append the bandwidth parameters underneath