Modern Meida Copy Protection

[colorfixer]

The issue revolves around the macrovision placing white boxes in the vertical blanking interval. Modern TVs of the time fully blanked the raster during the vertical retrace period (aka vertical blanking interval or VBI) to ignore captions and other signals there, vintage ones assumed a video signal that conformed to the standard of the time (nothing in these lines), so didn't blank the raster. The "stabilizer" simply blanked the video during the VBI.

The idea behind macrovision was a vcr would set the video recording level off the VBI so anything there would drive the vcr's recording level nuts. Old early VCRs did not have an automatic video recording level control (it was preset), so they were "immune".