Defeating copy protection

[Gary Bettan]

We've been selling a cheap $100 stabilizer from Sima the SCC. It works very well on removing copy guard form VHS and DVDs.

Gary

[Bradley Miller]

The graphics guy,

The reason your industrial Panasonic decks duped the Macrovision tape is simple. Macrovision puts five squares in the vertical interval bar of the NTSC image. Those five squares do two things. First they come on at full brightness, tricking the recording VCR's automatic video gain circuit into thinking that the picture is "too bright" and to "turn it down", thus you end up with a VERY dark image. Then after 30 seconds or so of that, the Macrovision signal takes those 5 squares and starts flashing them on/off/on/off/on/off for another 30 seconds or so and then repeats. This tricks the AGC circuit into constantly and quickly turning the video level up and down and up and down, resulting in the alternating light/dark video. The theory here is that ONE of these two evils will trick most any VCR on the market. (Although back in the day I found it quite easy to simply order the repair manual and solder in an outboard mounted potentiometer in place of the AGC circuit on the board. All that is needed is the circuit board schematics. And yes, this was for legal viewing of tapes, for not all monitors, including mine, were immune to Macrovision's signal when it first came out.)

If you have an ancient television that has a manual "vertical hold" (remember that?), you can play a Macrovision encoded tape and carefully alter the vertical hold control on the tv and bring the vertical interval bar (sort of like a frameline) down into the picture and see the Macrovision signal in pure form.

With VHS/S-VHS, the AGC circuit is before the recording and the playback is without any form of video control. This is what Macrovision was based around. This is also why LaserDiscs and Betamax could never use Macrovision, for their AGC circuits were placed AFTER the playback circuit. Thus, if you have a Betamax tape with Macrovision, you wouldn't be able to play it without those effects.

So getting back to your point, the reason why your industrial Panasonic decks duped the tapes is because those are commonly set up to mate with each other and there is no AGC circuit. These are also basically the same VCR design/circuit that is used in professional duplication houses, so a manual video level control was a necessity in order to make the Macrovision tapes in the first place. The bad news is that even if you took a duped tape on that setup and tried to dupe it at home or into the computer, the Macrovision signal will still be there waiting to attack.

Now steadichupap posted that he bought a Panasonic 2 channel WJ-AVE5 "video mixer". I also have one of these. It came out in the early 1990s as an alternative (and substantially cheaper) solution to genlocking video signals for A/B roll editing. What the units does is completely ignore whatever data is in the vertical interval bar, and re-create it digitally. This allows one input to be off by any amount from the other signal and when switched, there will not be a "roll bar", like what happens when you switch tv channels on some televisions (where the "frameline" rolls up to the top of the screen quickly). An unintentional benefit of this is that it completely strips Macrovision from the signal. Plus, you have a freshly generated vertical interval bar, which generally produces better dupes on that aspect alone (especially when you dupe a tape that is not an original to begin with). Beware though that if you have closed-captioning, the WJ-AVE5 will strip it too, since the CC coding lies in the vertical interval bar.

Hope that helps clear a few things up.

(BTW videoguys, "Copy Guard" has not been used since the early 80's. It was a highly ineffective system designed to create uncontrollable rolling of the video signal and although you are obviously talking about Macrovision in the post above, using the term "copy guard" is actually a trade name for a very old and outdated product.)

[Mike Butler]

Wow! Thanks for an amazingly clear and detailed explanation. Now, having seen that, I decided to try taking a page out of steadichupap's book, and dug out my Panasonic WJ-MX10 (basically the same thing, a little cheaper version), remembering how it enabled me to mix an A-B roll without needing a genlock or Time Base Corrector, and now I know why. Brilliant, guys! I haven't used this thing since going NLE anyway, but now it is useful again. So far, it works fine on DVDs, I'm sure it will be equally fine on VHS tapes.
Cheers!

[Ted Jan]

Hmmm...a couple of years ago...you could buy several different models of DVD players that allowed you to turn off the Macrovision protection. Apex 600 was one of these models that allowed you to turn off the Macrovision protection.

I know that there are still a number of these DVD players floating around...whether or not anyone wants to part with them is a different story...

[Rob Lohman]

Most players still can. Sometimes they need to "patched"
by a shop that can do it, sometimes they need a firmware
change and other times it is just a couple of codes you need
to enter.... Just for your information.

I was (and still am) having a great deal of trouble with my ATI All in Wonder Radeon, one of the problems being DVD playback (AC-# sound SPDIF out specifically). Anyways, $60 in tech support calls later, ATI suggested I use a win2k beta version of the drivers for the card and I found that macrovision everything worked EXCEPT the macrovision. The macrovision "device" showed up as "uknown device" in the device manager, but the DVD and AC-3 audio played back with pristine clarity. I would never suggest someone buy this card, but if you happen to own one, the driver set is W2K-755-010523B and was (and may still be) available on ATI's support site.

Secondly, I made some shorts a few months ago and I managed to do exactly what you are trying to do with little to no difficulty. The way I did it was to download divx copies of movies I LEGALLY owned and then chopped them up in an NLE program on the computer.

-Cocobutt

[Ben Stineman]

I was having issues capturing from a macrovisioned VHS movie when capturing with StormVideo, I would get the audio with mostly gray video. I then analog captured via s-video in Premiere6 and I no longer have trouble with MV. I have a brand new StormSE and the 1.5 driver. It's as if Premiere6 doesn't have the MV detection enabled in it's capture driver.

just a thought.

BDOG