Rolling Old School With Copy Protection From The 1980s

Oh, for the old days when sailing the seas of piracy was as simple as hooking a couple of VCRs together with a dubbing cable. Sure, the video quality degraded with each generation, but it was so bad to start out with that not paying $25 for a copy of “Ghostbusters” was a value proposition. But then came The Man with all his “rules” and “laws” about not stealing, and suddenly tapes weren’t so easy to copy.

If you’ve ever wondered how copy protection worked in pre-digital media, wonder no more. [Technology Connections] has done a nice primer on one of the main copy protection scheme from the VHS days. It was dubbed “Analog Protection System” or “Analog Copy Protection” by Macrovision, the company that developed it. Ironically, Macrovision the company later morphed into the TiVo Corporation.

The idea for Macrovision copy protection was to leverage the difference between what a TV would accept as a valid analog signal and what the VCR could handle. It used the vertical blanking interval (VBI) in the analog signal, the time during which the electron beam returns to the top of the frame. Normally the VBI has signals that the VCR uses to set its recording levels, but Macrovision figured out that sending extra signals in the VBI fooled the VCR’s automatic gain controls into varying the brightness of the recorded scenes. They also messed with the vertical synchronization, and the effect was to make dubbed tapes unwatchable, even by 1985 standards.

Copy protection was pretty effective, and pretty clever given the constraints. With Digital Rights Management, it’s easier to put limits on almost anything — coffee makers, arcade games, and even kitty litter all sport copy protection these days. It almost makes us nostalgic for the 80s.

[Itay] gave us the heads up on this one. Thanks!

47 thoughts on “Rolling Old School With Copy Protection From The 1980s

  1. I knew there was a reason I didn’t like TiVo.
    Frequently Macrovision tapes that were legal wouldn’t play after they had been played a few times. I blame Macrovision for my losing my legal copy of “Big Trouble in Little China.” Loved that movie.

      1. mandatory chip is mostly on dvd players to avoid VHS dubbing (well I’m not 100% sure macrovision chips are still in nowadays DVD players). In 199x I used a special software version of my creative DXR2 to disable macrovision and dubbed fragile DVD to more “children-resistant” VHS.

      2. No – this is incorrect. The Macrovision signal WAS recorded on VHS tapes.

        It was DVD players artificially added the macrovision signal to a clean output when commanded too by the content creator.

        So the DVD player “mod” to defeat macrovision was a chip that sat on the I2C bus listening for the command “Turn on Macrovision” and then instantly sent another I2C command “Turn off Macrovision”

        1. The mandatory chip added to the DVD players was the AGC in the record path. This made the signal recorded unstable and gave it a shift between a dark and a light picture, if recorded.

          IIRC, Macrovision fiddled about with the signal level on the back porch, round about where the colour burst was.

          Early cheap video recorders didn’t have an AGC and didn’t have the problem. (Expensive ones generally had the AGC anyway)

          The Macrovision chips (Unless you used another copy protection scheme. I seem to remember that PS2s used something different. There was also DCS) should still be in DVD players but maybe not Blu-Ray players. (Unless they have analogue out – unlikely)

    1. There were image stabilizers to remove the interfering signals. Some even available in electronic newspapers like “Elektor” or as kits. I still remember one from this magazine, it did not try to filter off the crap, but basically generated a new blank video signal which complied to the standard (PAL, NTSC) and was synchronized to the original video signal. Then there was a synchronous multiplexer which keyed the original image into the new clean line by line and frame by frame. Like cutting a piece of art out of its old, rotten frame and putting it in a new one.
      Ironically the older VHS machines from one of JVCs competitors – I think it was Philips – had a better implementation of the AGC which was more or less immune to the Macrovision interference. But JVC as license holder of VHS forced them to degrade the performance of their AGC circuit to make it susceptible to Macrovision.

      1. Radio Shack used to sell something similar. After a few years, they replaced it with another product with the same name “video stabilizer” that was just an amplifier.

    2. Lol, and many TVs could not cope with stronger ones. As I recall, “Kindergarten Cop”, “Say Anything”, and “Ghost” were particularly bad. We used those as test tapes, and I’ve seen the first five minutes of those movies sooo many times — “…it’s not a toomuh!” As I recall, the last one we made I designed around the LM1881, which simply gated out the signal. (VCR video signal really is horrible irrespective of Macrovision, but at least it had really clean sync after that!)

      We eventually got sued by Macrovision and had to quit selling them. They were legal in their own right under then current copyright law, but Macrovision cleverly had not only patented Macrovision itself, but it also patented (or bought, more usually) all sane methods of /removing/ Macrovision, as well.

      That line of business was about USD$ 90k/month, which was no small thing to lose for a Mom&Pop outfit. (I was neither mom, nor pop, so I continued earning my princely sum of something like $15/hr). Not entirely, but partially, this caused me to shift to software more, giving a couple years head start before the 90s Internet explosion, where new adventures laid.

      1. I seem to remember some of the Philips analogue video chips had VCR signal detection and, for example, would look on a couple of lines ifor various VBI signals if it didn’t detect a VCR signal and about 4 or 5 if it was.

      2. I built one using LM181 which stripped away all the Dutch pulses and added pseudo synch pulses at 64 microsec intervals. I could only ever get the pulses stripped out but could never get the pseudo synch pulses to add back into the composite signal. I eventually lost the scemantic in my piles of college work. Does anyone have a simple ircuit using An LM1881. My circuit only had on other chip in it which was an adders.

  2. How many of you had a little device that defeated Macrovision “protection”? They were small and relatively inexpensive, not to mention they worked great.

    1. I’ve got one of those. When this system was popular, The Rocky Horror Picture Show was just first coming available for sale on VHS. The tape was $90 and I was able to get one (they were scarce) but it wouldn’t play on my VCR. The copy protection was cranked so high that even the original wouldnt play. I purchased a digital sync stripper that took out the blanking signal and recreated it and was able to make a copy that played beautifully. It’s ingenious that they came up with this and kudos to them, but as always, the hackers win the day.

        1. Back in the 80/90’s the rental videos came out after the cinema release and before the public release.
          They were often to be had for $90 and certainly much more money as they were going to be rented out to multiple people and thus were licensed and priced thusly.
          It could take as long as 4 years before you’d see a cinema release on terrestial TV in the UK.

        2. Back in the day? The tech was so new and the idea of “owning “ a copy of a beloved film was a novelty – I paid $125.00 for the first release of Star Wars. If you could find blank VHS tapes for less than $20 each – you bought a case of 10 – at least I did –

  3. In the ~2000s, film companies became so obsessed with digital piracy, that they started to neglect analogue copying and stop paying for ACP. This was known in the industry as the “analogue hole”, and Macrovision ran an ad campaign “plug your A-hole”.

      1. Sadly I never got my hands on a copy as it was US marketing’s work. We did manage to veto their anti-ripping ad which featured a chap who ripped DVDs called “jack”. U.K. marketing agreed it was so bad that they wouldn’t let us keep the proof.

  4. Ironically, for a company that was so hated, Macrovision was a great place to work for people like us. The atmosphere was really nice, pay and stock options were generous, R&D was encouraged and rewarded, and there was a hacking culture.

    1. Probably they had to “bribe” people to work for a copy protection scheme. Of course not as bad as working for a manufacturer of land mines disguised as child’s toys, but not much better.

  5. Please note that the early (circa 1980) “Copyguard” scheme which preceded Macrovision narrowed vertical sync only, Theory being that the recording VCR servo would be intolerant of short sync, but a direct viewer could tweak their TV for stability. At that time no slowly modulated flag in the vertical interval was done to muck with the recorder’s AGC. Countermeasures evolved and by the mid-80’s both methods were in the wild with single “stabilizer” devices capable of handling both.

    1. Thank you so much Roger for providing what I can find as the only explanation of how the original “CopyGuard” anti-copying protection of the late 1970s and early 1980s worked. Until recently, the only explanations I have found of this long since dead protection system was that it effectively weakened and altered the sync signals (how it does not say) so that the attempted copy would roll excessively making it unwatchable. It was not clear whether the second generation copy would have caused sufficient degradation to make it unwatchable or as you have pointed out that the recording VCR could not handle it. The only other explanations of CopyGuard was that it affected the TV as well and was abandoned because of jittery pictures and bending at the top of the screen. It appears that, as you noted, a video stabilizer designed to recreate the vertical interval and force all unwanted signals to black level would remove the problem, however it is not clear if a Macrovision immune VCR would be able to successfully record a CopyGuard encoded tape. Of course, Macrovision had the foresight to reportedly patent both the encoding and decoding schemes making (legal) black boxes harder to obtain, not to mention that it “obtained” manufacturer/licensing cooperation from the DCMA requiring the hardware to honor the protection.

  6. Those copy protections were also defeated by using a TBC (TimeBase Corrector) either a standalone one or a recorder with one inside (like some high-end Hi-8 decks). The TBC was regenerating all the “clocks” in the signal, keeping only the active video part of the original signal, so copy protection was indeed removed.

  7. A monitor two speakers a camera and two microphones, an a black box…. yet to see the “protection” that can defeat that, makes all this DRM just sound like what it is a sham…

    1. If you mean camcorder recording of a movie to copy it, those copies suck. Also they are no longer foolproof. Digimark has a digital watermark that can be inserted into an image that contains copyright info and serial number (each DVD has a unique serial number that is encoded in the watermark, so the source of any pirated copies can be determined). The digimark watermark encodes this data using very heavy amounts of FEC (forward error correction) so the amount of data after FEC has been applied is dozens of times larger than the original data, making it nearly impossible to remove the watermark, as even a heavily damaged digital watermark can be decoded to find the serial number and copyright info. This FEC encoded digital watermark is then scattered to all the pixels of the image using a pseudo-random number generator with a known random number seed, so that portions of the watermark will be in all parts of the image. Digimark decoders are coded with this random number seed so they know where to fetch the different bits of the digital watermark from in the image. With this technique, the individual pixels of the watermark don’t have to be bright, and can be quite dim actually and added to the existing image pixels, only slightly changing their brightness. The overall impact on the image is only a slight increase in what looks like background electronic noise in the image. However, if you copy it and give it to a friend, and the FBI catches the illegal copy your friend has, they can use their digimark decoders to decode the digimark watermark. From that they can check the macrovision database to see what store received the DVD from the manufacturer with that watermark (yes, serial numbers encoded in macrovision link to a macrovision database that has source information like movie studio, and even what store it was shipped to for original sale). From that, the FBI can go to that store, with the serial number and ask the store manager who bought the DVD with that serial number, and the store manager can query their inventory database to find that info. If the person bought the DVD with a credit card, then the customer’s name is on file, and that person would be YOU. Then you get busted by the FBI for piracy. If you paid in cash for the initial DVD, you won’t have a credit card linking you to your purchase, but the store database can still be queried for the time and checkstand number at which the sale took place that sold the DVD with that serial number. From there, the FBI can look at the store’s security camera footage covering that checkstand at that exact moment, and see the picture of YOU in the security camera footage. From there, all they need to do is print out a wanted poster, and wait for somebody who recognizes YOUR face in the wanted poster to rat you out to the FBI.

      As you can see, with this foolproof digimark watermark technology, you CANNOT avoid being caught, if you pirate movies.

      1. Crazy expensive new (or cheap and they don’t actualy work); I recently bought a good TBC/standard converter off eBay for $100. They don’t look that difficult to build for someone who reads this blog, and if good TBCs weren’t available used that would have been an option.

  8. Fascinating. I have often wondered how this “copy protection” was accomplished.

    I grew up watching (and sometimes trying to copy) rented VHS tapes. A friend of mine had a library of several thousand copied tapes! Now I find myself wondering what equipment they used to successfully make those copies. I’m certain I asked them at the time, but that was 30-ish years ago and my memory isn’t what it once was.

    Clever system!
    …Not that I approve of it.

  9. I used to get past this easily, connect the 2 vcrs with a 25 ft coil of coax cable, the integrated signal being modulated to channel 3 or 4 was part of the reason why tv’s could read it and vcrs, couldn’t. I came across this when I found the same distortion when i tried to feed the vcr into AV jacks on the back of the set. The recording quality wasn’t as good, but at the time I was splicing tapes together and there were other issues with that when it comes to quality, so i didn’t mind so much.

  10. I had a workstation with an ATI All-in-Wonder video card – had video input and an analog television tuner as well. The ATI drivers monitored for the macrovision signal and wouldn’t even play stuff that was protected. Wasn’t too much of an effort to patch the check out, then it became easy to frame grab (or wholesale record) from VHS sources.

  11. if you juuust happened to own an ILLUMINATOR / TARGA board you could use composite-in, turn on stablizer, then connect second VCR to (the?) composite-out.

    then you only need setup/test/preview software and not need actual capture/TARGA software and associated RAM/CPU/HDD resources.

  12. Frequently it’s claimed that Macrovision inserts fake sync signals in the VBI. This is NOT true. It actually inserts brighter than white signals in the VBI. This tricks the AGC in the recording VCR to decrease its gain, which dims the picture, and if it’s significantly brighter than white, the AGC cut down the gain so much, that the resulting signal out of the AGC will be so weak that the sync signals will be too weak to detect on playback (when the video is played back, it will cause a rolling picture on the TV). This inability of a TV to correctly play back a home-made copy of a Macrovision tape, has led to a HUGELY POPULAR (but also COMPLETELY INCORRECT) idea that fake sync signals are inserted by Macrovision, and there’s only one website I’ve read that actually has the correct information, but I forget what that website is now. In fact, sync signals are NOT brighter than white. Rather sync signals are actually darker than black, the complete OPPOSITE of the type of strong signal pulses that Macrovision inserts.

    There are several versions of Macrovision protection, and some of the later versions also mess with the chroma subcarrier during color burst, but at no point do they insert a fake sync signal, as that would prevent even a normal TV from playing the original copy of the video. Only thing that Macrovision may do to sync signals is slightly shorten the duration of each v-sync pulse (something that its predecessor did for sure, and it was called CopyGuard if I remember correctly).

    1. Check the Technology Connections video from around 4 minutes in where he actually shows what the VBI looks like. There’s the brighter-than-white parts, but also some blacker-than-black parts right before them. Those black parts are what people are calling the fake sync signals.

      On a TV they’re treated like extra h-sync pulses, but it’s outside the visible area anyway, and the vertical timing isn’t affected. Remember, those sync pulses are meant to almost directly drive the beam in a CRT, and as long as the beam ends up in roughly the right place nobody cares how it got there. On a VCR that’s actively trying to lock onto the signal for some purpose, it’s anybody’s guess how it will handle the unexpected pulses.

      1. Oops, I meant to say they COULD be treated like extra h-sync pulses, if anything. Alec’s old black-and-white set which he demonstrates with is clearly built more “to spec” and ignores those pulses as too short for h-sync, though there’s no practical reason to do so. That point still stands, it would not affect a TV when played directly.

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