1. Re: convert VHS to DVD
Re: convert VHS to DVD
Source: http://linux.derkeiler.com/Mailing−Lists/Fedora/2007−03/msg01609.html
• From: Tim <ignored_mailbox@xxxxxxxxxxxx>
• Date: Tue, 13 Mar 2007 19:35:01 +1030
Mike McCarty:
Actually, usually to remove MacroVision, one needs to *remove* the
quot;extraquot; sync pulses it puts in. :−)
It probably would have been best if I'd described the restoration
technique more accurately: You replace the syncs signal *and* vertical
blanking period. That takes care of almost everything in one go.
Macrovision may also play silly buggers with the chrominance stability,
most televisions don't notice it, but some VCRs do (you get weird
colouration distortions).
I fixed up the odd tape or two by playing it through a $3000+ analogue
vision mixer, it replaces everything outside of the horizontal and
vertical blanking periods with internally generated ones, and
DC−restores the signal. But that's not the sort of equipment that the
average person has to hand. I work in video production and got sick of
crap playback, so watched some movies through the desk.
I hadn't actually had a proper look at how Macrovision buggers up the
signal, my CRO wasn't brilliant at that sort of thing. I now have a
proper video waveform monitor, so I'll dig a disc out and have a look
using the delayed sweep.
You won't get a purpose−built quot;de−macroquot; box, not because of a patent
reason, but because of anti−piracy laws about circumventing such things.
Ah, but quot;Video Clarifiersquot; and quot;Video Stabilizersquot; are quite legal.
Many TVs don't deal well with the AGC fiddling done by MacroVision,
anymore than do tape recorders.
AGC issues are more to do with when there's a VCR between the player and
the TV set. If you connect a player to a TV set with a direct video
input, there's no AGC in the path. Macrovision's varying pulses (they
Re: convert VHS to DVD 1

2. Re: convert VHS to DVD
transcend upper and lower legal video values) upset the AGC in VCRs, and
can also upset the black level clamp in anything (VCRs or TVs) that
isn't able to ignore video signals during the blanking periods.
There is a simple circuit which needs a couple of pots adjusted
which kills most versions of MacroVision pretty handily. I haven't
built it, but I've looked over the circuit, and it should work.
http://www.hobby−electronics.info/projects/MacrovisionKiller.html
Hmm, output stage looks a bit simple, but a quick perusal at it looks
like it'd do the job. The kit I built was really only designed to make
it okay to watch a Macrovision−bastardised signal, rather than let you
record it. It did what it was built to do pretty well. That was really
all I was after, to be able to watch a movie on any telly set in the
house, and without needing an expensive dongle.
They also have disclaimers on them, like quot;This device is not for making
illegitimate copies of copyright material.quot;
I've got a couple of old monochrome reel−to−reel video recorders with a
badge stating the same thing riveted to them. ;−) I think the old
Umatic we had did, as well, but I got rid of that years ago. I'd have
to dig out the service manual to see if it listed it as a part. ;−)
DRM − Deny Replaying of Material...
−−
(This PC runs FC4, my others FC5 & FC6, in case that's important
to the thread)
Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.
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Re: convert VHS to DVD 2