>This is a little on topic, since it concerns a "classic" technology.
>I'm told that Macrovision is very VHS-centric, and as a consequence, it's
>without consequence when dubbed onto ?etamax, VCR or Video 2000, to name a
>few.
>I wish I had salvaged that VCR machine now... Not for piracy, I just like old
>video equipment.
Since I don't live in California (who has recently ruled it to be ok to
discuss how to bypass copy protection), I can technically be a heap of
trouble for saying this... but f-em.
Macrovision basically puts a signal in the vertical sync pulse that
confuses a VCRs auto adujustment circuitry. Normal VCRs (almost any that
you can buy today) will adjust for weak or strong signals to "normalize"
a video. Macrovision writes artificially strong or weak signals in that
pulse, so the "normalizing" distorts the image.
This is transparent on most systems during playback, as the adjustment
occurs at record time. But good high quality equipment, and many
projection TVs adjust on playback as well... causing the Macrovision to
kick in, preventing you from watching the video at all.
It will effect any system that depends on signal adjustment based on the
sync pulse. Basically VHS. They have also begun to macrovise DVD and
Satallite (which is going to start pissing off more people, as Satallite
owners are more apt to also own high end equipment that will be distorted
on playback). Things like 8mm, Beta, UMatic, won't be effected, because
they look elsewhere for adjustment (but if you dupe a macrovised movie to
8mm, and then back to VHS, it will still kick in, as the sync has been
carried over, but the 8mm copy will be clean).
To bypass it, you just need to either adjust the sync, or write a new
one. External macrovision defeating boxes tend to flatten out the signal.
Or you can use a TBC (time base corrector) to write a brand new pulse.
Or, in the case of what I do, my computer does it as a side effect. When
I dupe thru it, I am not actually copying the video, but rather recording
an NTSC conversion of what my computer screen is displaying. So the
original sync is never passed thru (so I get the same net result as a
TBC, without the benefit of being able to do A/B roll without gen lock
problems).
Now... to go a bit more off topic... I can be fined/jailed for sharing
this with you, because it is a violation of the DMCA. However, there is
NOTHING that I discussed here that I had to learn from "pirate" sites.
EVERYTHING I learned in collage during my assorted TV production classes
(I majored in TV/Theater production, well, at least until I dropped out
of school). If you have a half way decent understanding of TV production,
how macrovision works becomes an almost obvious no brainer, and how to
defeat it becomes an absolute joke.... but I can still go to jail... but
the MPAA/RIAA want you to believe the DMCA is a fair, just, and "good for
you" law!
-chris
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Received on Thu Nov 08 2001 - 18:50:03 GMT