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Author Topic: Analog Video Scrambling help (circuit or design)  (Read 3003 times)
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spyguy
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« on: September 21, 2011, 02:32:34 14:32 »

Hi

I have a need for a circuit or design for a video scrambling system. I need to scramble analog cameras between a 750 foot cable runs. I prefer a design or real schematic so I can also see how its done and build it myself. Preferred is cut and rotate type I would consider costs for IP core required for a DSP design. but anything good would be useful.
Any help appreciated

Thanks in advance

Mitch
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notes5
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« Reply #1 on: September 21, 2011, 06:03:11 18:03 »

Dear spyguy, an analog scrambler isn't simple to made... First the technology of an analog scrambler is old and is cheap to use a digital link. like a wi-fi camera.

Because is necessary to convert, synchronize and transmit into the cable a signal for 750 foot!!!

I researched some schematic, but nothing...

If you want to buy a video analog scrambler see this link, and remember that the couple will be required.

- http://rcdistributing.com/video_scrambler.php

73..

(note for moderator, if isn't possible to report a commercial site, please delete the link...)
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Notes5 isn't the original uploader, only a seeker...like a spider.
spyguy
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« Reply #2 on: September 21, 2011, 08:06:57 20:06 »

Thank you for the reply.
I know it is not a simple project. The manufacturer you list and some others like Ovation (sorry for commercial name) make the type of device I am looking for but want many hundreds of dollars per half system (yes you need 2 ) I also searched for such a system and found many references to 2 types of scrambling systems (Cut and rotate, and SSAVI (sync suppression and video inversion) these both apply to analog video and are currently in wide use even today. Cut and rotate is far better and is easier to make in a DSP. The line cut and rotate is not as difficult as it appears. It is based on counting lines, reading the video state of information (sync pulses, etc), cutting it in the right place based on timing and rotating. The lines that get cut and rotated and their sequence make up the encryption "key". A DSP can do it with easily but the coding and circuit are out of my capability. I was looking for a solution. Someone with the right skills could create this item. I saw a circuit for this some years ago but paid little attention because I did not need anything like this then.

Any comments or ideas are welcome

Thanks

Mitch
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« Reply #3 on: September 24, 2011, 02:24:28 14:24 »

If your library has issues of Radio-Electronics magazine or has them on microfilm, in the 80's and 90's they ran dozens if not hundreds of articles on sat TV, scrambling systems and such. I can't give you any specifics, but I remember they went into great detail explaining how the systems worked.
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fpgaguy
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« Reply #4 on: September 26, 2011, 08:16:06 20:16 »

probably easier to convert to digital on sending end and then pass through some core you can pick up from opencores

just depends on how secure you want really


The analog method of scrambling has been pretty much abandoned for security / reliability reasons


However if you still want to look at analog scrambling methods most of them involve hiding the horizontal or vertical sync and transmitting that data on some other band

Not directly applicable to what your doing




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mitsos
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« Reply #5 on: October 08, 2011, 05:34:58 17:34 »

hi

I think this article, gives you some ideas

http://ifile.it/hpqs4o3/unscrambling.pdf

regards
mitsos
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