decrypt VHS

[bkinalg]

How can I decrypt VHS tapes?

[Arachnotron]

What do you mean by decrypting VHS?

[dvd_maniac]

you must mean DE-"macrovision" a VHS tape? if so, what capture card do you use? and what software too?
I have ATI AIW and it has a way of getting rid of macrovision.

[dvd_maniac]

get a by pass device:
I think they are called RF converter. They are devices that you would buy from like wal-mart that allows you to hook up rca cables to a tv that does not have an rca hookups

[Arachnotron]

[Short disclaimer] Whether it is legal to copy macrovision protected tapes you own yourself to DVD or not depends on the law in your country. I don't know anything about that. If you are American, any action which has the word copy in it is probably illegal for you. With my explaination below I don't want to encourage anybody to do things that are illegal in their country. It is for your information only .[end disclaimer]

Macrovision works by adding some extra noise directly after the horizontal reference pulse. A VCR uses the difference between the horizontal ref and the blanking level directly following it to adjust the recording contrast. By adding noise in the blanking level, this adjustment goes haywire.

A TV does not do this adjustment and will simply ignore this.

Capture chips are also not affected by this. BUT they do detect the precence of the signal. It is up to the driver programmed by the device manufacturer to decide if it want's to do something about it. Some drivers will simply block the signal and go black. Others will ignore the signal and cheerfully grab everything regardless.

So:
choice 1: is finding a device/driver combination that ignores the macrovision signal.

Choice 2: There are some hacks around that will disable the detection in the driver for some devices.

Choice 3: There exist external copy boxes that filter out the macrovision signal and return the signal after horizontal ref to blanking level. They are often sold under eufemistic names as video signal improvers.

Be carefull with those. The more expensive (digital) versions need a s-video signal to operate, and if you feed them a composite signal they use a very cheap combfilter to separate Y/C. The resulting artefacts and resolution loss is terrible. Use them only if your VCR can output an s-video signal.
The cheaper versions that are composite only sometimes work, sometimes do not. Often there is quality loss.

All in all, go for option 1 or 2.