Date: Thu, 26 Mar 1998 09:26:51 +0100 (MET) From: Martin Husemann <martin@rumolt.teuto.de> To: etonumo@eto.ericsson.se (Ulltveit-Moe Nils) Cc: simons@rhein.de, freebsd-isdn@FreeBSD.ORG Subject: Re: Fax Message-ID: <199803260826.JAA05450@rumolt.teuto.de> In-Reply-To: <9803251001.AA18606@dinosaur> from "Ulltveit-Moe Nils" at Mar 25, 98 11:01:24 am
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> This is probably not implemented. No, it is not implemented. > Implementing G3 fax in ISDN would mean simulating an analog modem > on the digital link. This means having to generate the right waveforms > for the modulated data, and receive analog data from the other end > which you had to run FFT analysis on and then interpret. Probably not an FFT, a simple IIR filter might do (but I'm not good enough in signal proccessing to be sure) > In addition you have to do this in realtime, to be able to deal with > the timing involved in the fax protocol, something neither > FreeBSD or Linux is good at in their native form.. Not that hard real time. You know, you can do this on a 486/33 running Windows 3.1 - so you realy should be able to do this on any BSD with a 486 or better. I once looked at doing this (and might reconsider doing it just for fun if I get hold of all the neccessary standards for less than a few thousand dollars). I use an active card (with very limited on-board resources) and would try to handle at least parts of the d/a and a/d, if not all of the G3 protocol, on the card itself. But since you can't easily debug there, I would first implement a pure kernel based version. Anyway, your real point "use dedicated hardware" is correct. That's why I have a paper fax now. Martin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isdn" in the body of the message
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