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Old 12-15-2014, 08:11 PM
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miniman82 miniman82 is offline
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TBC question: macrovision removal?

K, so I did as others have suggested and incorporated a professional rackmounted TBC (time base corrector) to my home broadcasting rig. Trouble is I still have macrovision in my vintage sets, and I thought a TBC was supposed to cure that. It's a FOR A FA-310 model, and it seem to be in working order. All the pots behind the front panel (like chroma phase and background) work like they should, even freeze frame works like it's supposed to. Any reason a high end TBC wouldn't remove macrovision? Have I blown $100 for nothing here?

More on the rest of the rig later, that's a separate post.
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Old 12-15-2014, 08:53 PM
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Could be that it does not replace or adequately clean the vertical synch where the crap lies...I've got a few consumer TBCs that make tape look good (the main design objective of a TBC), but won't touch macro-vision....
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Old 12-15-2014, 09:20 PM
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Quote:
Originally Posted by Electronic M View Post
Could be that it does not replace or adequately clean the vertical synch where the crap lies...I've got a few consumer TBCs that make tape look good (the main design objective of a TBC), but won't touch macro-vision....
Your guess is as good as mine, Tom. I can't find a manual for it online, so I can neither confirm nor deny. It's a piece of pro equipment, so I can't think of a reason for it not to completely strip and reinsert sync. Here's an Ebay link to one just like it:

http://www.ebay.com/itm/For-a-FA-310...item4184a68490


I'm at a loss, I just wanna watch a damn movie!
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Old 12-15-2014, 09:40 PM
Chip Chester Chip Chester is offline
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Do you have a link to a manual for your TBC? (Now looks like no.) Does it have a white clip adjustment? Adjustment for which vertical interval lines are blanked? (I may be remembering BetaSP VTRs rather than TBCs on the blanking.)

(Remarkably, the one on koppix.net has one for a buy-it-now price of $11.)

Chip

Last edited by Chip Chester; 12-15-2014 at 09:46 PM.
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Old 12-16-2014, 01:28 AM
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TBC manufacturers are understandably a bit reluctant to say whether their products will strip Macrovision. In practice I understand that industrial/professional TBCs will do this. They will certainly insert new blanking and syncs.
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Old 12-16-2014, 05:50 AM
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I don't see a white clip pot on the front panel, but it may be an internal adjustment. Won't know unless I can come up with a manual. I guess I still need a macrovision stripper.
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Old 12-16-2014, 10:22 AM
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The problem is visibility in retrace; a white clip may reduce it, but will not eliminate it. The offending pulses need to be replaced with blanking level.
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Old 12-16-2014, 12:13 PM
Chip Chester Chip Chester is offline
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It was my understanding (from long ago...) that the macrovision signal in the vertical interval went significantly over 100% in order to provoke the automatic gain control and get their desired effect. There are several 'normal' signals that exist in the vertical interval -- closed-captioning, vertical-interval timecode, vertical-interval test signals, and Neilsen data among them. They all are "allowed" up to 100%, so a macrovision signal limited by clipping to 100% shouldn't cause gain control problems. Have I actually tried this to defeat macrovision? Nope, never had the cause, or time, to do so. So if others actually have tried it, with a tweakable tbc monitored by a scope, I'll of course defer to their direct experience. But I do know that VITS, the vertical-interval test signal, often uses a one line of full 100% colorbars to do its business. So if a auto-level control can handle one line of full level in the VBI, I would think it could handle five (or whatever) if clipped to 100%.

I recall hearing at the time that RF out from the playback deck, routed to RF in of the record deck, was a way to evade the issue. Quality would be not-so-great, though.

I do know many small broadcast switchers totally rebuilt the VBI, as well as pro TBCs or frame synchs, because they would be the first place to look when closed-caption data was being mistakenly stripped from a known-good captioned source. A switcher or effects box that will do a simple wipe will also take care of the matter.

Looking at the macrovision wiki reveals folks that have been sued or absorbed due to their success in defeating macrovision. That would be the beginning of my search for a solution on the used gear market.

Good luck!
Chip
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Old 12-16-2014, 08:14 PM
Gregb Gregb is offline
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Sorry I don't know all the techno stuff about this but I do know that I bought one of these off that auction site and it works awesome!! The picture is free of that macro nonsense and crystal clear.

http://www.ebay.com/itm/Digital-Vide...item2a479e1918

Gregb
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  #10  
Old 12-16-2014, 08:55 PM
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I recall there was a Hitachi-made GE VCR top-loader model early '80s that would blank out all the copyguard and other stuff in the vertical interval, even with E-E signals passed through its Video input, so it would be gone when playing back on one of their TVs with the Vertical Interval Reference "VIR" automatic picture control. Seems the wow and flutter time base errors added to the tape playback caused havoc with the TV's VIR working properly, so they just stripped it from the video through that VCR. The mechanically similar Hitachi branded model did not have that.
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  #11  
Old 12-17-2014, 01:39 AM
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I remember when Macrovision encoding was first used on movie tapes, and it turned out that the system had been only designed and tested on VHS VCRs. So, anyone with a Beta VCR could copy rented tapes just fine! (Except for the fact that home-format tape-to-tape copies were rather lousy quality in any case.)
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Old 12-17-2014, 02:48 PM
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Most machines had a Macrovision detector that would block the record button signal from activating the record circuit, VCRs without that circuit (such as pre-lawsuit ruling Beta decks which were built that way on purpose) would record a macrovision laced signal Macrovision and all to tape without a care....In fact if one can identify the macrovision detector stage in any VCR or video recording device and disable it then it should be possible to copy a macrovision protected signal (albeit perhaps with AGC confusion effects) without stripping the mac...
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Old 12-17-2014, 10:13 PM
Chip Chester Chip Chester is offline
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Finding and defeating AGC would do it. In fact, on the wiki, there was mention of a US law barring import of any VCR without AGC, simply because the macrovision process relies on it.

Chip
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Old 12-18-2014, 07:36 AM
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Yah if you can defeat the AGC that would do it. And there were very inexpensive
boxes that use to be for sale that would do it.... In the days of Wometco Home Theater
over broadcast tv in NJ it was a home brew activity to build yer own little box for that.
It involved restoring the sync pulse to its proper amplitude. I imagine its just about
the same for macrovision.

This is the way the box use to be advertised, just like this one on ebay today....

-------------- This is from the ebay ad link above ----------
Digital Video Stabilizer w/ Copyguard


*
o Brand new! in the box!
o Eliminates video related symptoms: brightening, darkening, color shifting, jitter, shake, & more...
o Stops rental movie picture problems.
o Removes all picture distortion caused by copy protection. Enables copying of videotapes
to DVD by removing copy protection. Back up your videotape collection to DVD.
o S-Video or Analog input
o Analog cable included
o AC Adapter included
o Works for first and second generation Macrovision.
o Model: SD6038


----------------------

It's the brightening and darkening of the pic, it makes a copy loose sync.
I think it would be cool to get one and reverse engineer it....


.
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Old 12-18-2014, 07:56 AM
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Quote:
Originally Posted by Electronic M View Post
Most machines had a Macrovision detector that would block the record button signal from activating the record circuit...
Only machines I ever saw when I repaired them for a living that would block or shut down the Rec mode were the later model Go-Video units after they (Sensory Science Corp) lost the lawsuit against them. Put in a tape, hit "copy" it would run for maybe 5 seconds until it detected macro-crap, and shut off with a blue screen message. Other VCRs would simply record garbage for an hour or two.
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