[bbs-revival] VoIP Modem and Wardialer for the 2020

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Fabio Pietrosanti (naif) lists at infosecurity.ch
Fri Jan 3 08:06:58 UTC 2020


On 02/01/2020 22:56, Harald Welte wrote:
> This is pretty much what I had in mind, too - although not specifically for
> wardialing, but simply for any use case.

Yes, we also realized that focusing our current and past effort on 
trying to get a working "voip-modem" is much helpful than making a "voip 
wardialer" (because, for example, beave's iWas could work fine exposing 
a pty with basic AT emulation).


>> The design is a bit "creative" but it's done a way to make the "Software
>> DSP" issue pluggable and remote (now Asterisk-Softmodem connected to a local
>> asterisk).
> As you can see at http://osmocom.org/projects/linmodem/issues I had the plan
> to do this based on the linmodem code from Fabrice Bellard (who needs no
> introduction).  The code implements more different modems/standards than
> the asterisk code, and it's not really tied to the winmodem hardware - it simply
> consumes and produces 16bit samples, so all that's needed to attach it to RTP
> is to do the aLaw/uLaw table lookup.

I think that yours is "the right approach" from a technical standpoint 
of view.

What we tried to achieve is "something working" by gluing together all 
of the pieces, leaving for another pizza-hackaton improvements and 
stabilization.

It's *likely* that Asterisk-Softmodem doesn't provide the performance 
and stability we want (sometime is connect, sometime it does not 
connect, sometime it gives your garbage, anyhow still missing CONNECT 
and reporting of negotiated carrier speed).

So the world still miss the missing piece of a features voip-modem that 
also provide a pty.

I added osmcom linmodem to the "Software Modem" section 
https://github.com/x25today/voipwardialer#software-modem .

>
> But hey, my approach is still vapourware and yours is implemented, so who
> am I to make suggestions.

We're working to try to make this working with a commandline and 
extendit piece by piace, but really without the real 
telecommunication-grade effort-and-skills to fix the DSP problem 
properly, assuming that someone with that knowledge will help in hooking 
one of the cool and complete softmodem.

Linmodem is surely a way to go, we also spotted this nice soft-modem 
that by reading the specs seems very very interesting for it's 
integration opportunity (connecting pty and audio i/o) and the careful 
timing consideration https://github.com/randyrossi/fisher-modem .

Did you ever saw / considered this?

-naif



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