Date: Wed, 18 Mar 1998 12:18:58 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: jonny@coppe.ufrj.br (Joao Carlos Mendes Luis) Cc: rhh@ct.picker.com, eivind@yes.no, hasty@rah.star-gate.com, multimedia@FreeBSD.ORG Subject: Re: What is teletext (was Re: "Windows 98" program guides) Message-ID: <199803181118.MAA00596@labinfo.iet.unipi.it> In-Reply-To: <199803181223.JAA06747@gaia.coppe.ufrj.br> from "Joao Carlos Mendes Luis" at Mar 18, 98 09:23:02 am
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> // These data are encoded with a very simple NRZ modulation (black=0, > // white=1) of the video signal, with a frequency of approx 6.75 MHz. > > This is the dot freq, right ? So it must be less on NTSC and/or PAL/M. not really sure about that, but if you browse the net looking fo "VBI" you should find out. > Do you have some soft algorith for this ? I'd like to peek at those > digital lines I see. Maybe there is a Station to Station command > to inform about commercial beginning and end. I could use it to > mute fxtv. :) the ttxt.c code from my page does the soft decoding. there is some uk site with info on teletext formats (again i forget the URL but altavista is your friend). > Do you know if Closed Caption info is sent by this way ? If so, > generic Hauppauge model 400 can also receive this, as the windows > driver seems to be able to do that (but I could not test yet). i think yes, closed caption go on these lines although perhaps with different data rates etc (i guess so since there were some projects using the PIC microcontroller to decode closed-captioning and i doubt the PIC can go so fast... so perhaps closed-captioning is only a few bits per line), since you have 50-60 fields/s and that's more than enough for one line of text, probably even at 1-2 bits/line cheers luigi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message
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