[Freeswitch-dev] Possible bug in FreeSWITCH regarding RTP retagging of video (FS-6640)

Jean-Paul Iribarren jeanpaul.iribarren at free.fr
Tue Jul 1 16:54:12 MSD 2014

Hi FreeSWITCHers,

I think I may have found a bug in FreeSWITCH regarding video forwarding
in a call center configuration.

Basically, when an extension calls a call center number (setup with
mod_callcenter), and a call center member replies to the call,
FreeSWITCH may end up forwarding video with a wrong RTP type once it has
connected both legs of the call. This error is dependent on the codec
configuration of each part.

This happens e.g. when caller has H.264, when callee has H.263 and
H.264, and when FreeSWITCH is configured with H.263 and H.264 (in this
order). In such a case, FreeSWITCH initially negotiates H.263 with the
callee, and ultimately, it ends up forwarding H.263 data from the callee
to the caller, but it erroneously re-tags it as H.264 at RTP level.

Since in this case, H.264 is the common capability of all participants,
perhaps a H.264 renegotiation should have been initiated by FreeSWITCH
before beginning to forward data?

I have created FS-6640 on Jira to describe this issue, including an
attached Wireshark trace. Please refer to this bugnote for details.

Many thanks in advance for having a look.

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