From 27d6d323590197bd0bc93d028afd076dee19cff6 Mon Sep 17 00:00:00 2001
From: Dave Horton <daveh@beachdognet.com>
Date: Wed, 26 Jan 2022 07:37:09 -0500
Subject: [PATCH] bugfix: rtpengine needs to transcode when different codecs
 are used on A and B legs

---
 lib/tasks/dial.js                   |  3 +--
 lib/utils/place-outdial.js          |  6 ++++--
 lib/utils/strip-ancillary-codecs.js | 30 +++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 4 deletions(-)
 create mode 100644 lib/utils/strip-ancillary-codecs.js

diff --git a/lib/tasks/dial.js b/lib/tasks/dial.js
index 514824ee..e89810fc 100644
--- a/lib/tasks/dial.js
+++ b/lib/tasks/dial.js
@@ -554,8 +554,7 @@ class TaskDial extends Task {
     try {
       const aLegSdp = cs.ep.remote.sdp;
       const bLegSdp = sd.dlg.remote.sdp;
-      this.logger.debug({aLegSdp, bLegSdp}, 'Dial:_releaseMedia - releasing media from freewitch');
-      await Promise.all[sd.releaseMediaToSBC(aLegSdp), cs.releaseMediaToSBC(bLegSdp)];
+      await Promise.all[sd.releaseMediaToSBC(aLegSdp, cs.ep.local.sdp), cs.releaseMediaToSBC(bLegSdp)];
       this.epOther = null;
       this.logger.info('Dial:_releaseMedia - successfully released media from freewitch');
     } catch (err) {
diff --git a/lib/utils/place-outdial.js b/lib/utils/place-outdial.js
index 7fd1be70..7f415f58 100644
--- a/lib/utils/place-outdial.js
+++ b/lib/utils/place-outdial.js
@@ -8,6 +8,7 @@ const ConfirmCallSession = require('../session/confirm-call-session');
 const AdultingCallSession = require('../session/adulting-call-session');
 const deepcopy = require('deepcopy');
 const moment = require('moment');
+const stripCodecs = require('./strip-ancillary-codecs');
 const { v4: uuidv4 } = require('uuid');
 
 class SingleDialer extends Emitter {
@@ -316,9 +317,10 @@ class SingleDialer extends Emitter {
     return cs;
   }
 
-  async releaseMediaToSBC(remoteSdp) {
+  async releaseMediaToSBC(remoteSdp, localSdp) {
     assert(this.dlg && this.dlg.connected && this.ep && typeof remoteSdp === 'string');
-    await this.dlg.modify(remoteSdp, {
+    const sdp = stripCodecs(this.logger, remoteSdp, localSdp) || remoteSdp;
+    await this.dlg.modify(sdp, {
       headers: {
         'X-Reason': 'release-media'
       }
diff --git a/lib/utils/strip-ancillary-codecs.js b/lib/utils/strip-ancillary-codecs.js
new file mode 100644
index 00000000..5442b873
--- /dev/null
+++ b/lib/utils/strip-ancillary-codecs.js
@@ -0,0 +1,30 @@
+const sdpTransform = require('sdp-transform');
+
+const stripCodecs = (logger, remoteSdp, localSdp) => {
+  try {
+    const sdp = sdpTransform.parse(remoteSdp);
+    const local = sdpTransform.parse(localSdp);
+    const m = local.media
+      .find((m) => 'audio' === m.type);
+    const pt = m.rtp[0].payload;
+
+    /* manipulate on the audio section */
+    const audio = sdp.media.find((m) => 'audio' === m.type);
+
+    /* discard all of the codecs except the first in our 200 OK, and telephony-events */
+    const ptSaves = audio.rtp
+      .filter((r) => r.codec === 'telephone-event' || r.payload === pt)
+      .map((r) => r.payload);
+    const rtp = audio.rtp.filter((r) => ptSaves.includes(r.payload));
+
+    /* reattach the new rtp sections and  stripped payload list */
+    audio.rtp = rtp;
+    audio.payloads = rtp.map((r) => r.payload).join(' ');
+    return sdpTransform.write(sdp);
+  } catch (err) {
+    logger.error({err, remoteSdp, localSdp}, 'strip-ancillary-codecs error');
+  }
+};
+
+module.exports = stripCodecs;
+