[Asterisk-Dev] Coefficient values in fskmodem.c

[Tony Hoyle]

Hi,

I need to add a couple of extra frequencies to fskmodem.c.  It currently 
supports 1200/2200hz keying for Bell102, and I want to add V23 support 
(1300/2100hz).

There are some comments in spanish(?) about how the coefficient values 
are generated, but my knowledge of bandpass filters (and spanish) is 
almost zero so there isn't enough to help:

/* Coeficientes para filtros de entrada                                 */
/* Tabla de coeficientes, generada a partir del programa "mkfilter"     */

:(

I have a copy of mkfilter but it's not as simple as saying 'I want to 
filter 2100hz'.. there are lots of options and different types of 
filters... the website version comes close but feeding in (or example) 
1400hz to see if I get the same back that's already defined, gives 
totally different results.

At the moment I'm just hoping I'll get away with the 100hz difference - 
there's less than a second of data - but it's definately better to do it 
right.

Is there anyone on-list with enough of a maths background to make some 
sense of this part for me?

Tony

-- 
All your code belongs to Santa

Tony Hoyle <tmh at nodomain.org>  Key ID: 104D/4F4B6917 2003-09-13
Fingerprint: 063C AFB4 3026 F724 0AA2  02B8 E547 470E 4F4B 6917
Phone(FWD): (0845 004 5566) 413300