TBC question: macrovision removal?

[Findm-Keepm]

Originally Posted by miniman82

Thanks Greg, just got it in the mail and it works! No more macro crap, and cheap too! Only question now is, what to do with this apparently useless TBC? It does have neat features like freeze frame and picture and chroma adjustments in it, but in truth I can't see retaining it. Anyone want it for what I paid? I think it was $100 shipped.

It would be interesting to see the internals of one of those - to see how close it is to the old Macrovision Scrubber circuits we used to build. Radio Electronics had a first-generation one in the Dec 87 issue - it works, but the second generation Macrovision (non-tape media) made it almost obsolete.

[Phil Nelson]

Originally Posted by miniman82

Thanks Greg, just got it in the mail and it works! No more macro crap, and cheap too!

Hey, I have one of those. I got it years ago. I thought the (then) company had gone out of business, because the link I posted in a website article stopped working long ago. Maybe they changed distributors or something. No idea what's inside, but it gets the job done.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[ChrisW6ATV]

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.)

[Electronic M]

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...

[Chip Chester]

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

[Ed in Tx]

Originally Posted by Electronic M

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.

[Penthode]

I would not consider using a time base corrector specifically to remove macrovision. A timebase corrector is designed to address the variable write and read head to tape velocity variations which leads to playback time base error on video tape. It may as an option, include means to blank lines in the Vertical Blanking Interval but there is no guarantee as this is not the device's primary purpose.

In the old days of analog television broadcast, a video processing amp was inserted at the output of a studio production video switcher or the output of TV station feeding the transmitter. The processing amp would re-insert horizontal and vertical sync pulses and color burst and would generally include the ability to blank unwanted lines. Whether the Time Base corrector or Processing Amp devices can blank the macrovision lines immediately after the vertical sync is another question. The manufacturer may have obliged us by including this extra feature.

I personally would tend to avoid a timebase corrector as they often degrade composite video quality. The time base corrector would unnecessarily decode the NTSC chroma, the luma and chroma would be digitized, then re-clocked and then go through digital to analog conversion and then the NTSC chroma would be re-modulated. The quality of the resultant video depends upon the cost of the Time Base Corrector. The Processing Amp is perhaps a better choice as it would only replace the video sync and the color burst: the active video will be untouched.

The simplest solution may be simply to build a device with monostables to blank specifically the macrovision lines.

[Username1]

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....


.

[miniman82]

Probably uses logic gates to strip the original pulses and replace them, there's not much inside it I can tell you that much. A power supply, and a few IC's is about it.

[miniman82]

Can't do it without the box!

[Dude111]

[old_tv_nut]

Originally Posted by Dude111

The video is not processed digitally in this box, as far as I know. There certainly are pulse/timing circuits to fix the blanking interval.

[Chip Chester]

It looks like the one in Radio Electronics counts lines, and switches a newly-generated vertical interval in place of the macrovisioned-one. So, the actual program material you see is unaltered, not digitized and processed. All the information needed to build your own seems to be in the article, probably including the artwork for the circuitboard. You can mail-order boards made on a one-off basis, and populate it yourself if the parts are still available.

It's quite likely that the $50 version does things the same way...

Chip

[miniman82]

Honestly it's $50 well spent, I just hope it lasts a while because it's certainly made in China...

[Olorin67]

does anyone know the model number of that Radio Shack modulator, I see a lot on ebay, but hard to tell which is which.