Supplemental "telephone-event" codec lost when using "allow-asymmetric-codecs" flag

[lassebm]

rtpengine version the issue has been seen with

12.5.1.47+0mr12.5.1.47 and 14.2.0.0+0mr14.2.0.0 (master)

Used distribution and its version

Debian GNU/Linux 12 (bookworm)

Linux kernel version used

No response

CPU architecture issue was seen on (see uname -m)

x86_64

Expected behaviour you didn't see

When transcoding between AMR-WB/16000 and PCMA/8000 using the allow-asymmetric-codecs flag, the supplemental telephone-event codecs for both clock rates are kept towards the caller.

Unexpected behaviour you saw

The telephone-event/16000 clock rate is removed towards the caller breaking DTMF compatibility with some providers. The allow-asymmetric-codecs flag is used for logic in abbc022. The telephone-event/16000 clock rate is kept without using the allow-asymmetric-codecs flag.

Steps to reproduce the problem

• Patch rtpengine-ng-client to support allow-asymmetric-codecs flag:

  $ sed -i '/asymmetric-codecs/a\        allow-asymmetric-codecs' rtpengine-ng-client

• Send UA offer:

  $ rtpengine-ng-client offer --call-id=foo --from-tag=foo --codec-transcode=PCMA --codec-transcode=G729 --allow-asymmetric-codecs --sdp-file=<(cat <<EOF
  v=0
  o=- 886916473740350 1145423270 IN IP4 10.10.10.10
  s=-
  c=IN IP4 10.10.10.10
  t=0 0
  m=audio 60818 RTP/AVP 96 97 8 98 99
  b=AS:80
  a=rtpmap:96 AMR-WB/16000
  a=fmtp:96 mode-change-capability=2; max-red=0
  a=rtpmap:97 AMR/8000
  a=fmtp:97 mode-change-period=2; mode-change-neighbor=1; max-red=0
  a=rtpmap:8 PCMA/8000
  a=rtpmap:98 telephone-event/8000
  a=rtpmap:99 telephone-event/16000
  a=ptime:20
  a=maxptime:20
  EOF
  )

  Received rtpengine offer:

  v=0
  o=- 886916473740350 1145423270 IN IP4 10.10.10.10
  s=-
  c=IN IP4 10.42.42.42
  t=0 0
  m=audio 34102 RTP/AVP 96 97 8 18 98 99
  b=AS:80
  a=maxptime:20
  a=rtpmap:96 AMR-WB/16000
  a=fmtp:96 mode-change-capability=2; max-red=0
  a=rtpmap:97 AMR/8000
  a=fmtp:97 mode-change-period=2; mode-change-neighbor=1; max-red=0
  a=rtpmap:8 PCMA/8000
  a=rtpmap:18 G729/8000
  a=fmtp:18 annexb=yes
  a=rtpmap:98 telephone-event/8000
  a=rtpmap:99 telephone-event/16000
  a=sendrecv
  a=rtcp:34103
  a=ptime:20
  

• Send UA answer:

  $ rtpengine-ng-client answer --call-id=foo --from-tag=foo --to-tag=bar --codec-transcode=PCMA --codec-transcode=G729 --allow-asymmetric-codecs --sdp-file=<(cat <<EOF
  v=0
  o=root 1112911144 1112911144 IN IP4 10.20.20.20
  s=-
  c=IN IP4 10.20.20.20
  t=0 0
  m=audio 43694 RTP/AVP 8 18 98
  a=rtpmap:8 PCMA/8000
  a=rtpmap:18 G729/8000
  a=fmtp:18 annexb=no
  a=rtpmap:98 telephone-event/8000
  a=fmtp:98 0-16
  a=ptime:20
  a=maxptime:150
  a=sendrecv
  EOF
  )

  Received rtpengine answer with missing telephone-event/16000 clock rate:

  v=0
  o=root 1112911144 1112911144 IN IP4 10.20.20.20
  s=-
  c=IN IP4 10.42.42.42
  t=0 0
  m=audio 34638 RTP/AVP 8 96 98
  a=maxptime:150
  a=rtpmap:8 PCMA/8000
  a=rtpmap:96 AMR-WB/16000
  a=fmtp:96 mode-change-capability=2; max-red=0
  a=rtpmap:98 telephone-event/8000
  a=sendrecv
  a=rtcp:34639
  a=ptime:20
  

Additional program output to the terminal or logs illustrating the issue

Anything else?

No response

[rfuchs]

You can test with e0bca3a if you want, but this should improve the situation