[Freeswitch-users] zRTP + OPUS one-way audio issue

[Andrea Mazzeo]

Hi,

I'm facing an one-way audio issue with zRTP while using OPUS. zRTP is set
in passthru mode.
Called party can hear Calling party but not vice versa.

Full log:
https://pastebin.freeswitch.org/view/639adfe9

This issue is happening *only* with dynamic payloads codecs.
Everything is working fine if I use G722 or G729.

Scenario Leg-A (207) -> FS -> Leg-B (213)

Checking FS logs, I see

Leg-A's SDP:
a=rtpmap:103 opus/48000/2

Leg-B's SDP:
a=rtpmap:102 opus/48000/2

Actually having different payloads should not be an issue.
I opened a case to Acrobits, they said the issue is in the actual RTP
traffic sent to Leg-A from FS:

>From the client log Leg-A
Sending RTP packet #200 192.168.128.158:59176 > 31.102.111.134:28560,
len=116, really=116,
data=80679E55DF67E34A291167D899830CC03C124F353DA3C069574410EC0333125F
This is using 103, correct as agreed on this side of the call

Received RTP packet #200 31.102.111.134:28560 > 192.168.128.158:59176,
len=90,
data=80663D3B22CC8CB414490864A230F49B6EFF42E7BCA9EB64B864374B1377965C
This is using 102, which is wrong for this side of the call.

Seems that after negotiated payload 102 with Leg-B, FS is trying to use it
on Leg-A, where it should be used 102 instead.

Any idea?

FreeSWITCH Version 1.8.1-2-4f54cff~64bit (-2-4f54cff 64bit)
OS.: Debian 8.11
Linux pbx-186 3.16.0-4-amd64 #1 SMP Debian 3.16.51-3 (2017-12-13) x86_64
GNU/Linux

Thank you,
Andrea Mazzeo
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