Why are DVDs not as robust as CDs?

[Ron Stone]

Watching a movie the other night with friends, we had to abandon a new DVD after the player was unable to track it. One of them is involved with technology services, and opined that this was why DVDs should not replace CDs for everyday data storage -- too fragile, she said. (Ironically, it turned out the DVD player was at fault.)

I always assumed that DVD was really just a denser, more tightly-packed CD. Why do I run into more trouble with even very lightly scuffed or dusty discs? The same faults on a normal CD don't seem to cause mistracking on even cheap players. Is it the nature of the smaller DVD pits to be more easily mistracked or misread, or do DVDs lack oversampling, etc.?

Or am I just more aware of DVD errors due to the immediate visual confirmation of problem (often projected through a large home theater screen with surround-sound)? My sample is not scientific -- it may be a case that almost all my DVDs are rentals, so they've been treated more harshly than CDs I own.

[Sckott]

IMHO, no.

DVD's and CDs both can fail if treated poorly. Ironically, DVDs and CDs will fail very easilly if damaged a certain way.

Some scuffs and scratches can make a CD or DVD mistrack, usually ones in "circular" directions, sometimes the scratch doesn't need to be very deep. "Radial" ones don't seem to effect play at all.

Then the player and the ability to track poorly kept discs is a big factor. It's not that different than Cds, Playstation discs, Data discs, VCD or other formats. A circular-written polycarbonate disc is prone to sensitive damage.

There's a remedy I use for very, very scratched discs, and I've only had to do it to a CD once in my life. It involved using a Skip Doctor gadget and then polishing the disc with Lemon Pledge....

[Dave D]

I have yet to encounter any problems with DVD's...or DVD-A's. My 45a seems to work like a charm. I had Xmen skip on me on my old Panasonic, but there was a nice heavy scratch on the disc. Rentals tend to get beat up.

[Ken_McAlinden]

The information density on a DVD is something like 7:1 compared to a CD, right? Twice that on a dual-layered disc, IIRC. They are probably more susceptible to scuffs and scratches for this reason.

Regards,

[Damián]

Rental DVD movies can be quite a problem (around here, at least). Several times I've got discs with big greasy fingerprints smeared on them or hopelessly scratched, or both.

Some played a bit better (or at all) after washing the disc(s) with warm water and soap.. I don't give a damn if it's not the right way to do it, it's not my disc.

It does make you wonder just what some people do to their CDs though. Also the store staff themselves sometimes write a number (an ID, I presume) right on the disc in big fat marker, nevermind if it's a double-sided disc with one format on each side..

[aashton]

Originally posted by Ken_McAlinden
The information density on a DVD is something like 7:1 compared to a CD, right? Twice that on a dual-layered disc, IIRC. They are probably more susceptible to scuffs and scratches for this reason.


Ken is heading in the right direction - because of the differing data densities, track widths and tolerances of CD and DVD it would appear that DVDs are more susceptible to dirty surfaces but more resilient to physical damage. Or so the man from Del Monte he say.

Enough for the insomniacs here.... :)

http://www.pioneer.co.jp/crdl/tech/dvd/2-e.html


All the best - Andrew :)

[Matt]

Polishes like Lemon Pledge or Turtle Wax (the latter I've never used, but some have) seem to work well with scratches.

Toothpaste actually 'works,' though your disc sure as hell won't look good. I only used it once, for a CD that had some really bad scuffs that totally obscured the surface, sort of clouding it in a way. It worked, but the whole surface now has microscopic marks running from center to edge all over the place.

[Michael]

That's interesting...I've played over 650 DVD's in my Tosh SD-3109...never had a single glitch:) I'm considering the Pioneer all in one player mentioned over in the hardware section as a second player...:thumbsup:

[Drew]

The "Yes: Live From the House of Blues" concert DVD from Beyond Music has been known to become unreadable after about 2 years. The copy in my collection happens to be one of them. :(

[therockman]

I have collected optical discs since early 1984, and I have never encountered a manufacturing defect with either CDs or laserdiscs, I have bought about 1,500 CDs and about 300 laserdiscs. But I have encountered 2 manufacturing defects with DVDs, PINK FLOYD THE WALL LIVE IN BERLIN, and LED ZEPPLIN DVD set, both of these discs had problems that made them unplayable in every machine I was able to try them in. I don't what that say's, but I sure hope that this quality control is not indicative of an entire industry problem.

[sgraham]

I haven't had any problems with dvd's yet, but it stands to reason they'd be more fragile than CDs because of the increased information density. A scratch will wipe out a whole lot more bits.

[Tim Casey]

For the second time in two days, I think sgraham has hit the nail on the head - the same scratch will wipe out a lot more info on a DVD than on a CD.

Added to that is the fact that it's a less mature medium. I'm pretty sure I had a lot of skipping CDs back in the mid-eighties, but I rarely see any defects nowadays.

[aashton]

Originally posted by sgraham
I haven't had any problems with dvd's yet, but it stands to reason they'd be more fragile than CDs because of the increased information density. A scratch will wipe out a whole lot more bits.

Maybe yes, maybe no - there could be some counter intuitive elements in the technology ;)

From Pioneer


Finally, 0.6 mm substrates are at a disadvantage when it comes to surface dirt and damage. Since the pickup beam diameter at the disc surface is only one-half that of the diameter for the 1.2 mm substrate, the DVD pickup is twice as sensitive to surface dirt and damage. This disadvantage is compensated for by using powerful error correction schemes. The CD format provides correction for error bursts up to 2.29 mm long, while the DVD format can correct for error bursts as long as 6.0 mm & more than twice as long. And when it comes to scratches, the CD information layer is covered only by protective lacquer and the printed surface, making the information layer quite vulnerable to scratches on the label side. The DVD, on the other hand, is actually composed of two bonded substrates. Since the information layer is protected by a full 0.6 mm substrate, it is much less vulnerable to label-side scratches than a CD.

All the best - Andrew

[Drew]

The Yes concert DVD I mentioned above doesn't have a scratch on it. I can't even get my DVD-ROM on my PC to recognize it. I'm trying to find the article on nfte.org (one of the best YES information sites on the web) that explains specifically what happens to this title but it has nothing to do with tracking, it just becomes unreadable on any drive after about 2 years.

I did a quick google search thru newsgroups and I found this is the alt.music.yes usenet archive:


I received your letter today regarding defective HOUSE OF YES: LIVE FROM THE
HOUSE OF BLUES DVDs. I have indeed gotten some complaints regarding this
disc, and have replaced every disc sent to me with a newly-manufactured
copy.

Please send your disc to my attention and I will replace it. It is not
necessary to send the packaging, just the disc itself.

Please also let any of your contacts know I am equally willing to replace
their DVDs.

I am disappointed that you perceive a lack of response from Beyond on this
matter. As far as I know, everyone with whom I've interacted has received a
replacement disc in a timely manner. I have sent discs as far as Indonesia
and Japan.

Here is where to send the disc:

Dean Buckley
Production Manager
Beyond Music
9255 Sunset Bl. 2nd Fl.
West

[ybe]

My copy of House Of Blues stopped working some time ago. I ordered it from Amazon about three years ago. Haven't sent it to Beyond yet. Drew, the address you posted is not complete. The whole address is:

Dean Buckley
Production Manager
Beyond Music
9255 Sunset Bl. 2nd Fl.
West Hollywood, CA 90069

[njwiv]

Originally posted by ybe
My copy of House Of Blues stopped working some time ago. I ordered it from Amazon about three years ago. Haven't sent it to Beyond yet. Drew, the address you posted is not complete. The whole address is:

Dean Buckley
Production Manager
Beyond Music
9255 Sunset Bl. 2nd Fl.
West Hollywood, CA 90069

Guys,

I hate to say this, but I heard that Beyond went out of business a couple of years ago (not long after releasing the Go-Go's reunion album).

Jay