TBC question: macrovision removal?

[Penthode]

I would not consider using a time base corrector specifically to remove macrovision. A timebase corrector is designed to address the variable write and read head to tape velocity variations which leads to playback time base error on video tape. It may as an option, include means to blank lines in the Vertical Blanking Interval but there is no guarantee as this is not the device's primary purpose.

In the old days of analog television broadcast, a video processing amp was inserted at the output of a studio production video switcher or the output of TV station feeding the transmitter. The processing amp would re-insert horizontal and vertical sync pulses and color burst and would generally include the ability to blank unwanted lines. Whether the Time Base corrector or Processing Amp devices can blank the macrovision lines immediately after the vertical sync is another question. The manufacturer may have obliged us by including this extra feature.

I personally would tend to avoid a timebase corrector as they often degrade composite video quality. The time base corrector would unnecessarily decode the NTSC chroma, the luma and chroma would be digitized, then re-clocked and then go through digital to analog conversion and then the NTSC chroma would be re-modulated. The quality of the resultant video depends upon the cost of the Time Base Corrector. The Processing Amp is perhaps a better choice as it would only replace the video sync and the color burst: the active video will be untouched.

The simplest solution may be simply to build a device with monostables to blank specifically the macrovision lines.