I've just recently purchased some VCDs that seem to have been "overburnt." What I mean by that is that each CD has more data (approximately 720 MB) than the standard capacity (about 650 MB), and some of the PC CD-ROM drives are having difficulties reading them. Are there any hardware/software fixes that could work around this problem? Do DVD players/drives handle them fine?

-- John Y Ahn (desertnocal@yahoo.com), December 27, 1999

Answers

There is not an "overburn". What happens is that a standard CD holds up to 650 MB of USEFUL DATA, which is not the same as 650 MB of total data. This is because many bytes available in the CD are used for error handling (detection & correction) thus are not counted.

Because an "error" in some pixels or frames of a video stream is not as relevant as an error in software-type data, VCD maximizes the capacity of the CD, allocating for useful data (=video+audio)lots of bytes that a standard data-CD would use for error correction.

The relation between useful data in a VideoCD vs. DataCD is 2324/2048, so mathematically speaking a VCD can hold up to ~1.13 times as much so called "data" as a regular CD.

-- Matias (petrellm@telefonica.com.ar), December 28, 1999.

Thanks for the info, but that still doesn't answer the essence of my question. How come my drives can read VCDs that are under capacity without a problem yet have problems reading over-capacity VCDs?

-- John Y Ahn (desertnocal@yahoo.com), December 28, 1999.

Matias did a great job in explaining why a VCD can hold 2324/2048 X 650 =~ 737MB of data. In another form, the capacity of a VCD is 74 minutes of playtime.

Please imagine filling a cup full with water. Can the cup hold over- capacity of 1 cup of water? Your claims that your VCDs are being "over-capacitied" can only be a fiction of your imagination.

If your player cannot play your VCDs 100%, it is most likely that your VCDs are not 100% "good" - a very common phenomenon associated with pirated VCDs.

-- TOMO (ong@worksafe.wa.gov.au), December 29, 1999.

Okay, fine, if you want to berate me for semantics, so be it! All my VCDs are legitimate as far as I can tell. I was just curious as to why two different types VCDs -- ones with more than 650 MB of data and ones with less than 650 MB of data -- prompt different reactions from the several CD-ROM drives I have access to.

-- John Y Ahn (desertnocal@yahoo.com), December 29, 1999.

John,

Early CD-Rom drives and many ones made recently can not read newer CD discs. My laptop's 20x CD-Rom will not read any CD above 650mbs. I have to reburn my discs into the lower size to get them to work. It depends on who makes your CD-Rom and the speed. It is not "overburnt" as you put it. It is burned just like a regular disc because, in fact, those discs do exist. I have a stack of 80 minute discs that I use. These can not be read on my laptop. The only workaround is to either re-burn them onto 650 mb discs or get a new CD-Rom. Yes DVD players can handle any size CD just fine. I had a legit Titanic from Malaysia which was pressed on three 80 minute discs and my DVD player reads them fine.

-- The Lone Ranger (rutger_s@hotmail.com), December 29, 1999.

John, possibly the answer you were looking for is Lone Ranger's. But they are two different things: There are "normal"(74') CDRs and "big" (80')CDRs, the latter having a wider radius of active surface and thus not every drive is able to read them. What I say is that a *normal* CD (not the 80'CDs) can hold up to 737 MB if it is a VideoCD.

Given this, I cannot see why the same drive can read VCDs below 650MB because if your drive doesn't like blocks of 2324 bytes, then it shouldn't be able to read VCDs below 650MB, because their blocks are still 2324byte blocks. So I ask, are you 100% sure that those VCDs are white book compliant? Despite of the .dat file, it's very easy to fake this and the directory structure of a VCD in a regular (non WB compliant) CD-ROM.

Anyway, don't take it that seriously. Cheers,

-- Matias (petrellm@telefonica.com.ar), December 30, 1999.