Macrovision Decoder
I found a website (http://xedox.de/mac.html) the other day, which had plans for a Macrovision Decoder - but the text was in german. Thanks to the marvels of modern internet, I was able to translate it and I thought I'd include it here.
Note, I make no claim to the content or ownership of this, I'm just mirroring it in english. If you happen to read german, check the original site.
Note: If you just want to buy one, at the time of writing I had one for sale on the classifieds page.
Figure #1
Ingredients
- R1 : 1 x 27k ohm
- R2 : 1 x 68k ohm
- R3 : 1 x 680k ohm
- R4-R8 : 5 x 10k ohm
- R9 : 1 x 1k ohm
- R10 : 1 x 39 ohm
- R11 : 1 x 270 ohm
- R12 : 1 x 220 ohm
- R13 : 1 x 68 ohm
- R14 : 1 x 470 ohm
- R15 : 1 x 100 ohm
- C1-C2 : 2 x 100 nF
- C3-C4 : 2 x 1 nF
- C5 : 1 x 1uF
- C6 : 1 x 33 uF
- IC1 : 4098
- IC2 : LM1881
- IC3 : 4053
- IC4 : 4011
- OPA1 : LM324
- T1 : BC327
- T2 : BC549
- D1 : 1N4148
In a letter accompanying the original site, it mentions two components being missing from the component list (which I corrected), as well as several pointers. Roughly translated:
- "with 4053 the CS entrance on mass must be put"
- "with first monoflop I had to increase the resistance to 68 KOhm, since otherwise the lowest two noise stripes still came through"
How Macrovision Works
Macrovision has two modes, however I believe the most commonly used one (and what I believe this schematic will defeat) is the "AGC method". Basically, pulse spikes are introduced in the vertical blanking phase of the signal. While on most television sets, the result is completely un-noticeable, on almost every VCR the automatic gain control circuitry will get confused.
The end result is usually a picture that is dim (gain is reduced too much), may flash bright (as the AGC circuitry tries to correct itself between spikes), or may have brightly colored ghosts (though I have no idea why this occurs. The basic idea is it's less than pleasurable to view.
fwagglenote
I've not verified these plans, as I have no intention of building one. Your mileage may vary.
DMCA Warning
Note well: This article is provided for academic purposes only. If you live in an area that has DMCA-style legislation, building any device to defeat a copy protection mechanism is generally illegal. Consult your local legislation.