The analog hole is a loophole that allows music to be copied (infringed, or pirated, according to drm worshipper
s) by analog ripping. Heck, you can stand in front of your computer's speakers with a microphone and duplicate a content-protected file. You can also copy a DVD 'illegally' with your cell phone's camera. It's a concept that makes the RIAA/MPAA crap their pants, though not too much since the quality degrades with each generation.
Video signals can't be easily copied through the analog hole thanks to Macrovision.
The movie theaters installed many infrared LEDs facing the silver screen to plug the analog hole, because video cameras are sensitive to infrared light.