Macrovision

[Bayag]

I hear about it everywhere, someone please explain to me what it is.

This is the right forum I hope?

[Gazorgan]

Macrovision is a way of preventing you from copying copyrighted videos.

For DVD's, it's a bit set on the disk that signifies it's copy protected (the video isn't actually encoded wiht the macrovision).

For Tapes, the video actually has macrovision applied to it.

What is Macrovision? It's the slowly varying of the color subcarrier. What does this do to your TV? Nothing, it has an AGC (Automatic Gain Control) to correct for this. Your VCR is specifically built to not have this AGC circuit, hence you copies fade in and out and are of poor quality.

You will notice that some DVD players can turn the Macrovision off. Also, all new TV-out video cards have Macrovision enabled, so you can't play a DVD on your computer then TV-out it to your VCR.

There are numerous ways to circumvent Macrovision to backup what you own.

[FOO]

Macrovision modifies the video signal to screw up
VCRs. There are several different metods. I only know 2 of them.
Video has a Horizontal Sync pulse in it where the signal goes
way low (below black) for a short time. This tells the TV
to start a new horizontal sweep. Macrovision inserts a few
extra sync pulses before the real one. A TV has sweep circuitry
with large time constants (it can't change very fast) so it is not
affected. The vcr has different circuitry, it's not sweeping a beam,
and so it apprently is easily disturbed and the picture breaks up.
This screws up capture cards too but only because the manufacturers
deliberately detect Macrovision and refuse to record. (ATI)

The other method involves making the video signal go way too high
(white) during the vertical retrace. The TV doesn't care because it's
not in a field and has no AGC. The VCR has an Automatc Gain Control which attempts to keep the video at a constant level. When it sees super bright white it turns down the gain for the whole next field, and your TV
looks dark.

There is a (software) fix to prevent ATI cards from refusing to capture because of the sync problem but there's no way to fix the AGC thing.
So you can capture but the picture goes light and dark.

You didn't expect a whole textbook did you

[Bayag]

Aha, now it's clear to me!

Thanks for explaining, I appreciate it.