[Freeswitch-users] T38 Fax Fallback

[Mirko Brankovic]

I had a same question:
http://thread.gmane.org/gmane.comp.telephony.freeswitch.user/86263
Sorry google lead me only to this link...

On Dec 7, 2017 18:06, "Callum Guy" <callum.guy at x-on.co.uk> wrote:

> Hi All,
>
> I'll try and keep this simple.
>
> We are experiencing difficulty transmitting fax with a certain UK provider
> (BT) who have suggested the fix for the fault is that we "*should fall
> back to using G711 pass through in order to negotiate/ send fax*"
>
> The call initially connects with G711 (and the media is proxied).
> Fax is detected by the originator which issues a RE-INVITE request to use
> T38.
> This is rejected by the gateway with a 488 at which point we would expect
> the call to fall back to G711 however FreeSWITCH is reporting that this is
> not possible due to a media bug:
>
> "*Session is connected to a media bug. Re-Negotiation implicitly
> disabled.*"
>
> My understanding was that a media bug would be required for the initial
> fax tone detection which subsequently triggers the T38 session start?
> Could anyone confirm whether we need to be looking into closing off the
> media bug manually or if there is an alternative route to resolving this
> issue?
>
> We are running FreeSWITCH (Version 1.4.26  64bit).
> Calls are dispatched with setting "t38_passthru=true".
>
> Any help would be very much welcomed.
>
> Best Regards,
>
> Callum
> --
> Callum Guy
> Head of Information Security
> X-on
>
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