Why can't I play dvd's?
November 13, 2005 3:33 PM   Subscribe

I recently decided to jump on the dvd train, and finally bought myself a player. However, the video gives about 10 seconds of video followed by 10 seconds of blue screen. This from multiple players.

I have an old tv, and the dvd player goes through the vcr (nothing but coax input on the tv). Any ideas /suggestions?
posted by sauril to Technology (9 answers total)
Could be the Macrovision copy protection that's designed to stop you recording DVDs onto VCRs. It's only supposed to kick in when you're actually recording on the VCR, but some VCRs have problems even when you're just passing the signal through.
posted by chrismear at 3:45 PM on November 13, 2005

I worked for a retail store for a while, selling (among other things) DVD players. I have to agree with chrismear -- it's definitely the Macrovision protection.

You can pick up an adapter for $15-20 that'll convert your DVD players Red/White/Yellow composite video and audio plugs into a coaxial connection that'll plug directly into the TV, without going through the VCR first. (You can then plug the VCR into this adapter, so you've basically got the VCR going to the DVD going to the TV.)
posted by CrayDrygu at 3:48 PM on November 13, 2005

This is an artifact of "copy protection" on the DVDs you are attempting to watch. Macrovision copy protection causes the DVD to have weak sync signals. None of your alternatives are good, but they are:

1. New TV which has direct video inputs.

2. Insert a "video signal conditioner" between your DVD and VCR. This is probably illegal, but the devices are widely available over the internet.

3. An "RF Converter" may or may not help.

4. There may be a PROM upgrade available on the internet that would disable the copy protection. As with (2), this is probably illegal, and may void your DVD player's warranty.

posted by curtm at 3:48 PM on November 13, 2005

Definitely sounds like Macrovision to me, I had the same problem. To fix it, if there's no coax out on the DVD, you'll have to get an RF modulator. (Or a new TV.)
posted by squidlarkin at 3:49 PM on November 13, 2005

Thanks everyone, you all rock.
posted by sauril at 3:50 PM on November 13, 2005

Just to amplify on this a bit so it's perhaps more helpful to other people with this problem...

"Macrovision" copy-protection is merely a weakening of a particular part of the signal that makes up the picture and was primarily intended to prevent people from copying videotapes. I imagine almost everyone's seen it but probably didn't know what they were seeing: the resulting picture is a little jittery and is in black-and-white or alternates between black-and-white and color. The reason you're seeing a blue screen is because modern televisions, in the absence of a signal or a weak signal, will just show a blue screen instead of snow or a very poor picture. As mentioned above, you can get around Macrovision by inserting into your connections a signal amplifier that specifically amplifies the portion of the signal that Macrovision diminishes. But it's best to hook up your system in such a way that Macrovision copy-protection isn't an issue when you are merely watching a videotape or DVD.
posted by Ethereal Bligh at 4:09 PM on November 13, 2005

Some DVD players have 'easter egg' menus that let you disable macro-vision. here's one site with a bunch of links. It may be that you can disable macrovision with just your remote (Old APEX dvd players could do this)
posted by delmoi at 4:23 PM on November 13, 2005

There are two types of Macrovision. Type 1 fiddles with a part of the NTSC signal called the "back porch" that VCRs use to adjust the record level. The VCR expects this to be constant; by varying it, you convince the VCR that the signal level is constantly varying as well, and the VCR compensates by reducing or raising the level of the signal it is recording. Since the signal level isn't actually changing, this causes the recorded signal to be too low or too high much of the time, thereby ruining the tape.

Most TVs do not use the "back porch" for this purpose, so Macrovision Type 1 does not actually affect the viewing of a protected recording.

Most VCRs put the circuit that adjusts the signal level near the beginning of the signal path, rather than just before the signal goes to the heads. That means Macrovision Type 1 usually affects video passthrough as well as recording. This wasn't a problem until DVDs came upon the scene since most people don't chain VCRs together for the purposes of watching them.

The actual video on a DVD does not have Macrovision encoding. It's digital and doesn't have analog sync signals of any kind. Instead, if a flag on the DVD is set during mastering, the DVD player generates the Macrovision protection "on the fly" during playback. The reason not all discs have it is that they have to pay a license fee to Macrovision in order to use the flag. Nice racket.

As others have noted, there are plenty of devices that can generate a clean back porch to replace one that has been futzed by Macrovision. I am not a lawyer, but it's my understanding that it is not illegal to use a "signal conditioner" for purposes of watching video. (The DMCA would not apply because Macrovision is an analog technology.)

There is also a Type 2 Macrovision which futzes with the color phase information. As with Type 1, DVD players will generate this if a flag is set on the disc. Type 2 costs more to license than Type 1, so there are few discs that use Type 2. However, for completeness, you should make sure the signal conditioner you buy fixes both these types of "signal errors."
posted by kindall at 11:29 PM on November 13, 2005

as a followup, we bought an rf modulator, and watched dvd's to our hearts' content last night.

Thanks for all the answers.
posted by sauril at 10:40 AM on November 14, 2005

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