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Date Posted: 06:45:46 06/11/02 Tue
Author: Potter
Subject: Re: Help needed
In reply to: Stoyo 's message, "Help needed" on 01:00:23 06/11/02 Tue

You'll need to work with the cable signal in real time and use the cro to identify the scrambling. Work on the sync pulses first to see if they are present then check for suppression and inversion. If the sync pulses are not evident, the 3 chip design will not be be able to lock on to the signal and you'll need a different answer but in this case try to work out how the decoder gets its sync pulses (fixed data channel and audio sub-carrier are possibilities).
Be sure to check the VBI and non-visible lines as well as the visible ones. Very handy to have a cro with 'TV sync' triggering for this.
And - study the 3chip code very carefully to see if it does what's required from your cro observations and make changes as required.
Short cut - find a local who has already worked it out in part at least.

Good luck



>Dear Sirs, I need some help for descrambling local
>channel in my town.
>I don't know exactly what system is used and probably
>it is some variant of standarts. There is stable
>picture with video inversion like
>http://free.prohosting.com/~elin/cable12.html - video
>inversion (second picture)
>but with very high brightness and lines are shifted
>left and right more then on picture above.
>(it looks like RAIUNO, when scrambled, but there is no
>video inversion)
>System is PAL B/G
>I build 3Chip Rev3 board with PIC16F84A-20I. Have a
>try with f84palb, giln18 without any success - no
>lock. Have a try with 16F84A.asm from Dan with
>particular success - sometimes have lock, but it is
>unstable and picture is no descrambled - still video
>inversion, entire picture shifted to left. Standard
>quartz rezonator was used - no VCXO at this time.
>My questions are:
>Did any one can help me to identify scrambling system?
>I have 10MHz analog oscilloscope and at this time
>search for solution how to select which line to see on
>display, to see where are data packets to be able to
>modify the firmware.
>Did any one have experience with RAIUNO descrambling
>and can take me an advice.
>If I take source from recorded on VCR signal, did I
>can get descrambled picture or I must use directly
>signal, received from cable in real time.
>Please, excuse me for bad English.
>Best regards, Stoyo

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