make rtpengine transcode if non-preferred codec is selected by far end

lib/call-session.js

@@ -1,4 +1,5 @@
 const Emitter = require('events');
+const sdpTransform = require('sdp-transform');
 const SrsClient = require('@jambonz/siprec-client-utils');
 const {makeRtpEngineOpts, makeCallCountKey} = require('./utils');
 const {forwardInDialogRequests} = require('drachtio-fn-b2b-sugar');
@@ -49,6 +50,15 @@ const initCdr = (srf, req) => {
   };
 };
 
+const updateRtpEngineFlags = (sdp, opts) => {
+  try {
+    const parsed = sdpTransform.parse(sdp);
+    const codec = parsed.media[0].rtp[0].codec;
+    if (['PCMU', 'PCMA'].includes(codec)) opts.flags.push(`codec-accept-${codec}`);
+  } catch (err) {}
+  return opts;
+};
+
 class CallSession extends Emitter {
   constructor(logger, req, res) {
     super();
@@ -236,16 +246,16 @@ class CallSession extends Emitter {
       }
 
       // rtpengine 'offer'
-      const opts = {
+      const opts = updateRtpEngineFlags(this.req.body, {
         ...this.rtpEngineOpts.common,
         ...this.rtpEngineOpts.uac.mediaOpts,
         'from-tag': this.rtpEngineOpts.uas.tag,
         direction:  ['private', 'public'],
         sdp: this.req.body
-      };
+      });
       const response = await this.offer(opts);
       debug(`response from rtpengine to offer ${JSON.stringify(response)}`);
-      this.logger.debug({offer: opts, response}, 'initial offer to rtpengine');
+      this.logger.info({offer: opts, response}, 'initial offer to rtpengine');
       if ('ok' !== response.result) {
         this.logger.error(`rtpengine offer failed with ${JSON.stringify(response)}`);
         throw new Error('rtpengine failed: answer');

package-lock.json

@@ -22,7 +22,8 @@
         "drachtio-fn-b2b-sugar": "^0.0.12",
         "drachtio-srf": "^4.5.1",
         "express": "^4.18.1",
-        "pino": "^7.11.0"
+        "pino": "^7.11.0",
+        "sdp-transform": "^2.14.1"
       },
       "devDependencies": {
         "bent": "^7.3.12",

package.json

@@ -40,7 +40,8 @@
     "drachtio-fn-b2b-sugar": "^0.0.12",
     "drachtio-srf": "^4.5.1",
     "express": "^4.18.1",
-    "pino": "^7.11.0"
+    "pino": "^7.11.0",
+    "sdp-transform": "^2.14.1"
   },
   "devDependencies": {
     "bent": "^7.3.12",