Mostly macrovision is bad for ALL consumer VCRs.  The company that holds
the patents to key portions of the VCR requires licensees to add
automatic gain circuits to video inputs.  Macrovision pays them to
require this.  The macrovision signal then uses this fact, and many
other 'features' of consumer VCRs to cause problems with the video
signal that the VCR sees.

A normal TV, even old TVs, will rarely have any problem with these
offending signals.

One of the more common is to use the horizontal front and back porch
(the portion of the signal between lines as the beam traces back to the
next line) to hold a varying signal over several frames.  As these are
brought high, the AGC compensates over the whole picture, and darkens
the picture, as they are brought low the AGC swings the other way and
brightens the picture.

Other schemes cause color problems.  IIRC, they modify the color burst
signal(s).  The VCR requires very exacting color burst frequency and
phase, whereas a TV is somewhat more able to deal with slight
variations.  This can cause bad colors, and I think it's also
responsible for color banding, though that might be a different process.

Notice that the VCR is not so nearly exacting when it plays a video that
has macrovision in the signal, only when it is trying to record.

I found all this out with Cast Away and a new tiny media computer I was
reviewing.  My TVs are very old, and require a VCR or other method of
modulating composite and audio into rf.  I finally found a 'patch' for
my video driver which conveniently disabled the macrovision protection
built into the chipset on board.  DVDs do not have built in macrovision
- they simply tell the DVD player (software or hardware) to use
macrovision via a flag.  If macrovision is not built into the computer
complying players will typically not output a composite or s-video signal.

-Adam

Peter L. Peres wrote:

>In a rear projection tv the imaging element is likely not a picture tube.
>If it is not then the blemish could have a different cause from a station
>logo. You have to find out all you can about the type (use the Internet to
>get a manufacturer's data sheet or a test report).
>
>Macrovision is a system that puts all sorts of garbage into signals such
>that they are no longer standard and thus cause older tvs and vcrs to
>display incorrect images (too dark, jumping, color fading etc), in the
>hope that they will prevent illegal copying. It is meant to prevent
>illegal copying, and it is not very succesfull at that afaih. If you have
>any older equipment in your audio/video chain (esp. certain brands of
>expensive and long-lived color tvs) then do not buy anything marked
>Macrovision, since the picture quality will likely be bad at some time or
>other during viewing.
>
>Apparently ripped copies of Macrovisioned programs fix the Macrovision
>problem (on older equipment, see above) for private users ...
>
>Peter
>
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