Don't Bring Digital Knife To An Analog Gunfight
Macrovision has announced their deal with various well-known digital video download services to offer "ACP." That stands for Analog Copy Protection. Huh?
How can an analog protection system apply to digital video downloads? ACP works by embedding a signal in the vertical blanking interval, the time period after the display has finished drawing the image and is preparing to draw the next frame. For old VHS tapes, this was stored directly on the tape, but when the technology was ported to DVDs, it was stored as an instruction for the DVD player itself to create the signal on the fly. The signal causes analog recording devices to display wildly fluctuating artifacts, and on digital recording devices it triggers a flag that turns off the ability to record. Some DVD recorders have the ability to ignore the Macrovision signal, but most do not.
