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Date Posted: 05:51:49 08/26/01 Sun
Author: tvsync
Subject: 3chip PAL system with random CB inversion

Hi ALL,

(I've been away from all of this world because i have for several time (almost two years) a working system and my job takes away much time...)

But, as some of you know i, based on many hints from Dave2 site and the old Magicboxes site, devised a SX@50MHz box which can decode a cablecrypt system using only software (No VCXO!!! - In a PAL system it's very difficult to implement...).

For the ones which never came across a Cablecrypt system here are a few details: uses shifting HS & VS in a random way. The VS is totally distorted and those lines are used for the data transmission. Has random video inversion. And, last but not least, uses CB random inversion.

So I devised a method of clamping which does the clamping in the CB area since my HSync areas are random and a method of sampling the CB for seeing if it's inverted or not. And another simpler one for seeing if the video is...

The code is somewhat based on the initial code (the first versions which were vey modular, SIMPLY GREAT STUFF) of Jim from Magicboxes.. I upgraded it to 50MHz+PAL... and produced a Makeline procedure of my own which can mantain lock with a random HS..

I've talked with many persons in the past here in the board about the approach. I think what I done is nothing more than add many of the ideas presented here but in my own way.

As far as I know, my system is the only true 3chip project which decodes cablecrypt. I know some others but they use external sync chips to get locked...

I sent Sakman my CB amplifier circuit and my detectors circuit (they are level detectors!! Not edge detectors like the original 3chip!! - don't have that problem. Since i have a random HS zone it would be somewhat more difficult to manage the code to lock with edge detectors! But if it was necessary i would have done it...)

Hope this help someone.

I will answer any question but i may take awhile... too much work!!!

Bye to ALL

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