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Macrovision Wants Old DRM to Work Forever
Grv writes "Macrovision's best-known form of copy protection inserts noise into analog video signals to make it difficult to get a good copy of the DVD or VHS recording. A company named Sima has products that eliminate this noise when digitizing such video, as any good digitizer would do. Macrovision argues that this is a violation of the DMCA, and a court sided with them in June. Now the injunction is being reviewed, and several organizations are siding with Sima and Fair Use, including the American Library Association, the Consumer Electronics Association, the Home Recording Rights Coalition, and the Electronic Frontier Foundation. If it isn't overturned, this decision could make it illegal to develop products for making copies of commercial analog recordings."
This story selected and edited by LinuxWorld editor for the day Saied Pinto.
Basically this was sold as a way to prevent anyone from using two VCRs to copy a rented videotape. It (Macrovision) was placed on most commercial videos of Hollywood product from the mid-1980s to the present. Since the 'owner' of the video content had to pay a stiff license fee to Macrovision company, almost no porn tapes from that era had this nonsense added.
Macrovision is a burst of noise added to the vertical sync in the brief period after the current frame has ended and the next frame (a single 'photograph' or still image on the television set) begins. This burst of noise happened about once every ten to fifteen seconds. It caused the picture image to lose sync and 'roll' and/or 'tear up' for a short period of time until the vertical sync stabilization circuitry in the recording process
kicked in and made the picture stable.
This is how Macrovision was able to mess up the video copy without destroying the video integrity when watching the original commercial video tape. The sync stablizer circuitry only was active during the recording period, not during playback. But the video copy was polluted by tearing and rolling every ten seconds or so.
The way to defeat this pollution was/is to use an 1881 sync seperator IC, a track-and-hold circuit, a 4053-type analog 1-of-2 switch IC, and a timer on a microcontroller (or a 555 one-shot timer IC). Use the sync seperator to detect the beginning of the vertical sync pulse. At this time, sample the black video level using the track-and-hold. After sampling, switch the video signal to the recorder (for the content being copied) to the sampled black level for the period before the actual video image analog signal begins. Then switch the recording back to the analog video signal of the original. Your copy will be solid and without tearing and rolling.
Oh my goodness!?! Did I just break your fucking law by explaining this? Oh my, I am sooooooo sorry! Oh well, to quote Emil Faber, "Knowledge Is Good". That's from the first video that I thought was worth copying.