include codec-accept on answer to rtpengine during reinvites (#209)

* include codec-accept on answer to rtpengine during reinvites

* attempt to simplify

* fixes from testing

lib/call-session.js

@@ -1,5 +1,4 @@
 const Emitter = require('events');
-const sdpTransform = require('sdp-transform');
 const SrsClient = require('@jambonz/siprec-client-utils');
 const {
   makeRtpEngineOpts,
@@ -10,7 +9,6 @@ const {
   makePartnerFullMediaReleaseKey,
   isValidDomainOrIP,
   removeVideoSdp,
-  determineAnswerCodec
 } = require('./utils');
 const { MediaPath } = require('./constants.json');
 const {forwardInDialogRequests} = require('drachtio-fn-b2b-sugar');
@@ -96,19 +94,6 @@ const initCdr = (req, invite) => {
   };
 };
 
-const updateRtpEngineFlags = (sdp, opts) => {
-  try {
-    const parsed = sdpTransform.parse(sdp);
-    const codec = parsed.media[0].rtp[0].codec;
-    // Only add telephone-event support, don't restrict to specific G.711 codec yet
-    // This allows far end to choose between PCMU/PCMA freely
-    if (['PCMU', 'PCMA'].includes(codec)) {
-      opts.flags.push('codec-accept-telephone-event');
-    }
-  } catch {}
-  return opts;
-};
-
 class CallSession extends Emitter {
   constructor(logger, req, res) {
     super();
@@ -398,13 +383,13 @@ class CallSession extends Emitter {
       const toPublic = uris.some((u) => u.private_network === false);
       let isOfferUpdatedToPrivate = toPrivate && !toPublic;
 
-      const opts = updateRtpEngineFlags(this.req.body, {
+      const opts = {
         ...this.rtpEngineOpts.common,
         ...this.rtpEngineOpts.uac.mediaOpts,
         'from-tag': this.rtpEngineOpts.uas.tag,
         direction:  ['private', toPublic ? 'public' : 'private'],
         sdp: this.req.body
-      });
+      };
       let response = await this.offer(opts);
       this.logger.debug({offer: opts, response}, 'initial offer to rtpengine');
       if ('ok' !== response.result) {
@@ -516,7 +501,7 @@ class CallSession extends Emitter {
             })
           };
           const p = proxy ? ` via ${proxy}` : '';
-          this.logger.info({uri, p}, `sending INVITE to ${uri}${p}`);
+          this.logger.info({uri, p}, `sending INVITE${p}`);
         }
 
         /* now launch an outbound call attempt */
@@ -557,15 +542,16 @@ class CallSession extends Emitter {
             localSdpA: async(sdp, res) => {
               this.rtpEngineOpts.uac.tag = res.getParsedHeader('To').params.tag;
 
-              // Determine which codec to use based on far end negotiation
-              const {codec} = determineAnswerCodec(sdp, this.req.body, this.logger);
-
               const opts = {
                 ...this.rtpEngineOpts.common,
                 ...this.rtpEngineOpts.uas.mediaOpts,
                 'from-tag': this.rtpEngineOpts.uas.tag,
                 'to-tag': this.rtpEngineOpts.uac.tag,
-                flags: ['single codec', 'inject DTMF', `codec-accept-${codec}`, 'codec-accept-telephone-event'],
+                flags: [
+                  'single codec',
+                  'inject DTMF',
+                  'reuse codecs',
+                ],
                 sdp
               };
               const response = await this.answer(opts);

lib/utils.js

@@ -16,8 +16,8 @@ function makeRtpEngineOpts(req, srcIsUsingSrtp, dstIsUsingSrtp, padCrypto, teams
   }
 
   const srtpOpts = teams ? srtpCopy['teams'] : srtpCopy['default'];
-  const dstOpts = dstIsUsingSrtp ? srtpOpts : rtpCopy;
+  const dstOpts = JSON.parse(JSON.stringify(dstIsUsingSrtp ? srtpOpts : rtpCopy));
-  const srcOpts = srcIsUsingSrtp ? srtpOpts : rtpCopy;
+  const srcOpts = JSON.parse(JSON.stringify(srcIsUsingSrtp ? srtpOpts : rtpCopy));
 
   /** Allow feature server to send DTMF to the call excepts call from/to teams */
   if (!teams) {
@@ -41,6 +41,16 @@ function makeRtpEngineOpts(req, srcIsUsingSrtp, dstIsUsingSrtp, padCrypto, teams
     'replace': ['origin', 'session-connection'],
     'record call': process.env.JAMBONES_RECORD_ALL_CALLS ? 'yes' : 'no'
   };
+
+  const codec = {
+    accept: ['PCMU', 'PCMA', 'telephone-event'],
+    ...(process.env.JAMBONES_CODEC_OFFER_WITH_ORDER &&
+      {
+        offer: process.env.JAMBONES_CODEC_OFFER_WITH_ORDER.split(','),
+        strip: 'all'
+      }),
+  };
+
   return {
     common,
     uas: {
@@ -51,8 +61,7 @@ function makeRtpEngineOpts(req, srcIsUsingSrtp, dstIsUsingSrtp, padCrypto, teams
       tag: null,
       mediaOpts: {
         ...dstOpts,
-        ...(process.env.JAMBONES_CODEC_OFFER_WITH_ORDER &&
+        codec,
-          { codec: { offer: process.env.JAMBONES_CODEC_OFFER_WITH_ORDER.split(','), strip: 'all' } }),
       }
     }
   };
@@ -350,54 +359,6 @@ const removeVideoSdp = (sdp) => {
   return sdpTransform.write(parsedSdp);
 };
 
-const determineAnswerCodec = (farEndSdp, featureServerSdp, logger) => {
-  try {
-    // Parse both SDPs
-    const farEndParsed = sdpTransform.parse(farEndSdp);
-    const fsParsed = sdpTransform.parse(featureServerSdp);
-
-    // Get negotiated codec from far end (first codec in answer)
-    const negotiatedCodec = farEndParsed.media[0].rtp[0].codec;
-
-    // Get all codecs offered by feature server
-    const fsCodecs = fsParsed.media[0].rtp.map((r) => r.codec);
-
-    logger.debug({negotiatedCodec, fsCodecs}, 'determineAnswerCodec: analyzing codec negotiation');
-
-    // If far end negotiated G.711 (PCMU/PCMA) AND it was in the FS offer, pass it through
-    if (['PCMU', 'PCMA'].includes(negotiatedCodec) && fsCodecs.includes(negotiatedCodec)) {
-      logger.info({negotiatedCodec}, 'G.711 codec passthrough - no transcoding needed');
-      return {
-        codec: negotiatedCodec,
-        needsTranscoding: false
-      };
-    }
-
-    // Otherwise, we need to transcode to first G.711 codec in FS offer
-    const firstG711 = fsCodecs.find((c) => ['PCMU', 'PCMA'].includes(c));
-    if (firstG711) {
-      logger.info({negotiatedCodec, transcodeTarget: firstG711}, 'Transcoding required to G.711');
-      return {
-        codec: firstG711,
-        needsTranscoding: true
-      };
-    }
-
-    // Fallback: use PCMU
-    logger.info({negotiatedCodec}, 'No G.711 in FS offer, defaulting to PCMU');
-    return {
-      codec: 'PCMU',
-      needsTranscoding: true
-    };
-  } catch (err) {
-    logger.error({err}, 'Error determining answer codec, defaulting to PCMU');
-    return {
-      codec: 'PCMU',
-      needsTranscoding: true
-    };
-  }
-};
-
 module.exports = {
   makeRtpEngineOpts,
   selectHostPort,
@@ -414,5 +375,4 @@ module.exports = {
   makePartnerFullMediaReleaseKey,
   isValidDomainOrIP,
   removeVideoSdp,
-  determineAnswerCodec
 };