Like Magneto art on the screen.

October 13, 2021 4:16 PM

Do DvD security strips damage the DvD player?

Local library places two strips of what I assume are security strips with another layer of plastic. Some play fine, some look like a Pollock. I notice more scratches, more Pixel fun which no doubt strains the DVD player though it happens with a new disc with strip.
Is this standard as other libraries don't do this and I have no issue.

posted by clavdivs to Technology (5 answers total)

Generally, no, assuming the strips are placed carefully as not to unbalance the DVD.

Most DVD players don't care what's on the "back side" (i.e. label side) of the media. They'd only care if the spinning would cause the whole thing to wobble, and the disc is designed to handle far more than the specified speed.

For DVD and Blu-ray, the speed actually varies, from 1600 in the inner tracks to as low as 600 RPM in the outer tracks. But the disc itself is supposed to withstand spinning up to 32000 RPM, albeit, not with stuff stuck to the back of it.

Players are designed to handle the read with a little imbalance anyway. I wouldn't worry about it.
posted by kschang at 4:46 PM on October 13, 2021 [1 favorite]

The artifacts from damage to the disc don't harm the player in any way. The guts of the player are just the reader itself (a motor to spin the DVD and a laser+detector on a linear rail to read the tracks on the disc), and a little computer that decodes the data from the detector. The embedded computer reads whatever it reads, applies its error correction bag of tricks, and if none of that works, shrugs, and you get some noise in the video, or dropped frames. None of that does any harm whatsoever to the embedded computer doing the decoding, or the read circuitry.
posted by Alterscape at 7:06 PM on October 13, 2021

Don't let the news get out, but I used to clean the clear side* of rented DVD's with a few drops of neat washing-up liquid soap and rinsing off with cold water. It removed finger grease and dirt inside pits and scratches and helped the player correct errors it read.

*: the label side is quite thin foil and the edges can split the layers of the disk if you're really careless
posted by k3ninho at 12:18 AM on October 14, 2021

*: the label side is quite thin foil - kinda true for a CD, the pits and lands are "on the label side" with a thin layer of lacquer (and some ink) for protection. However DVDs have the "pits and lands" (microstructure that represents the data) sandwiched basically in the middle of the disc.
posted by achrise at 7:46 AM on October 14, 2021

And BDs are the "opposite" of a CD - Blu-Ray discs have the data encoded in layers on the "read" side and thus there is almost the entire thickness of the disc between the data and the label.

Put another way, to read a CD the read laser goes through almost the entire thickness of the disc before being reflected, on DVDs it goes roughly half-way through, and for BDs it doesn't goes into the substrate at all (multi-layer BDs have data built up in layers of lacquer on the read side)
posted by achrise at 7:51 AM on October 14, 2021