49 lines
1.7 KiB
Plaintext
49 lines
1.7 KiB
Plaintext
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Quick'n dirty Nagra/Syster descrambler.
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This set of files descrambles a 512x512 .PGM file containing a scrambled
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Nagravision/Syster image. The algorithm is easy and rather straightforward.
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It's not based on 'heavy' mathematical correlation techniques. The result
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however is not bad, and I'm convinced it can be optimized for speed (although
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it will probably be completely unusable for any real time decoding).
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How it works.
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A line can be divided in a number of slices. The number of slices is a power
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of 2. Meaning you can have e.g. 64, 128, 256 slices (or even 512 which means
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that every pixel is considered separately).
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The grayscale of every pixel is reduced to a number of levels (currently 4).
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This value was OK for the testimages.
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For every slice, the mean value of the grayscales is calculated. These mean
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values are compared later on to reconstruct the image.
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The program is written in Borland C++ (3.0 but others might also work).
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It's only a quick hack, so the code is not very good (actually it's full
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of what's considered bad programming practice ;-).
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You'll need a VESA compliant SVGA board (or a board supported by SVGA256.BGI)
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to run the program. On the upper right of the screen, a dot is flashing,
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indicating the program is processing the image).
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The program uses a resolution of 800x600x256.
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The GO.BAT file has a set of parameters which give a good result. On a
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486DX2-66 it takes about 3'12" to complete.
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Enjoy (?)
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Any comments are welcome.
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uvs@etec2.vub.ac.be
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crabbe@etec2.vub.ac.be
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*************************************
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PS.
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SuperVGA 256 BGI driver
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Copyright (c) 1991
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Jordan Hargraphix Software
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*************************************
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