[Spce-user] T.38 <-> G.711 Transcoding

[Gabriel Kuri]

Hi Richard,

Thanks for the info, I tried those settings and it seems to transcode.
However, sometimes the carrier does a T.38 Re-INVITE before the ATA does
the T.38 Re-INVITE, and C5 passes the T.38 Re-INVITE through to the ATA
rather than rejecting it and staying on G.711 on the carrier side. Is it
possible to reject the T.38 from the carrier side and stay G.711 so that
only the ATA side of the call does T.38 and the call is transcoded?

Gabe

On Tue, Sep 1, 2020 at 4:45 AM Richard Fuchs <rfuchs at sipwise.com> wrote:

> On 31/08/2020 12.56, Gabriel Kuri wrote:
> > Is it possible for C5 CE (using rtpengine) to transcode between T.38
> > (a-leg) and G.711 (b-leg) ?
> >
> > I've tried setting it up, but I can't figure out how to set the media
> > settings facing each leg (t38_force, t38_decode. etc.).
> >
> > Here's the scenario ...
> >
> > A-leg (T.38): Analog Telephone Adapter
> > B-leg (G.711): Carrier SIP Trunk
> >
> > On the A-leg, it would be good if we could force C5 CE to Re-INVITE
> > T.38 to the ATA immediately at the start of the call. But not sure if
> > C5 CE can do the Re-INVITE or if it must come from the ATA?
> >
> > On the B-leg, it would be good if we could stay on G.711 and refuse
> > any T.38 Re-INVITES that may come in from the carrier?
>
> Hi,
>
> So for the re-invite, that needs to be triggered from the ATA. The C5
> doesn't have the capability to trigger re-invites by itself right now.
>
> If you have a T.38 (re) invite coming from the T.38 ATA and you want to
> "break" it into a PCM invite going towards the carrier, you need to set
> the "T.38 decode" preference on the carrier side.
>
> If you have a PCM invite coming from the carrier and want to force it to
> be translated into a T.38 invite going to the ATA, you need to set the
> "T.38 force" preference on the ATA's side. But note that this would
> apply to all invites, not just those carrying fax PCM.
>
> Cheers
>
>
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>
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