View Full Version : Music CDs

06-02-1999, 01:37 PM
- - - While pondering the scratches on a favorite CD that are vexing track #1, I noticed that track #6 is the longest on the CD, but carefully looking on the laser-read side of the disk, I see that track #7 is longest. Do CDs always read in order like albums, or can they be set up to jump around and play tracks out of order? (-The outer edge of the CD is where the scratches are, and track #1 is skipping, so I assume that the outer track on the laser-read side of the CD is track #1.) - MC

06-02-1999, 01:57 PM
I don't know the answer specifically to your question (although I suspect they can be so arranged), but it was my understanding that CDs read from the inside out, which would make track #1 the one closest to the hole.

06-02-1999, 02:00 PM
I read "somewhere" that track 1 is closest to the center and that the laser starts there and moves closer to the edge as the disk plays. Have you tried cleaning the disk according to the instructions on the sleeve? This often solves skipping problems. I once took a CD I didn't care about and gave it a torture test. It took some very deep gouges before it was rendered unplayable.

06-02-1999, 02:07 PM
CDs are read from innermost to outermost part of the disc. If track #1 won't play, the scratches you think are responsible should be very close to the innermost part of the disc.

Preceeding the actual music is the information that comprises the table of contents. If that area is scratched badly enough, the entire disc is usually unplayable, since the player can't access the "playlist" & some other parametrical information it needs to get the disc playing.

The tracks usually get visibly thinner as you go out further on the disc because of the increase in linear storage space, assuming playing time per track is constant (one spiral "groove" is longer on the outer edge than on the inner edge, so there don't need to be as many to contain the same amount of data. If the last track appears to be "fatter/thicker" than the rest, it must be a helluva long song. Perhaps you're looking at the unrecorded "leftover" portion of the disc and thinking that's a track? An audio disc has 74 minutes of potential storage space on it, so add up the total time for music and see what's left. Hard to say without having the disc here in front of me so I can eyeball it & give you an official ruling.

06-02-1999, 02:50 PM
Opus is entirely correct. Also The encoding for CD's is not the same ad albums, which the grooves play the mucis when vibrating a needle, a CD has data encoded in lands and pits, somwhat similar to Morse code but not exactly.
This data is then fed into a processor that decodes the data into a usable format. THat is why computer CD's and Music CD's and Playstation CD's operate differently. Some CD readers will decode multiple formats, others, will not.

This encoded data may also not correspond exactly to the minute length of a song, depending on the amount of redundant data in the encoded bit stream.

To deal with men by force is as impractical as to deal with nature by persuasion.

06-02-1999, 05:28 PM
On a tangent, I have Squirrel Nut Zippers' Hot album on CD. It's primarily a music CD, but it advertises that it has some multimedia content. Every computer CD player I've put it on, though, simply freaks out and can't read anything from it. I can't even play the music from it through my computer's CD, which is a drag because I like listening to music at work.

06-02-1999, 07:18 PM
Greg, you're not alone. I was also unable to access the multimedia tracks on the "Hot" CD. Methinks they goofed, and maybe fixed it on later pressings of the disc?

06-02-1999, 09:03 PM
I have "Hot" and have successfully run the multi-media program. Don't know which "pressing" I got though.

IIRC, only about half of a CD is usable for music, due to the different speeds at which the data is passing by the read head. This isn't a problem for pure data, but it screws the music up.

Mastery is not perfection but a journey, and the true master must be willing to try and fail and try again

06-02-1999, 09:17 PM
IIRC, only about half of a CD is usable for music, due to the different speeds at which the data is passing by the read head. This isn't a problem for pure data, but it screws the music up. -- zyada
I think you are imagining vinyl-like properties with the CD. On a music CD, the music is pure data. CD's never hold anything but digital data, although the format varies.

You are probably thinking about the fact that the inner tracks are going to be smaller than the outer tracks. No problem. Even with music, CD spin speed varies. A music CD runs at about 500 rpms at the center, and about 200 rpms at the edge.

06-02-1999, 10:17 PM

I'm not familiar with that particular CD, but it could be an old CD-I (CD-interactive) format, which (thank God) fizzled out almost as soon as it was born. What puzzles me is you say that the CD says it has multimedia content, so obviously it need to be played on something that supports more than one kind of media. This effectively rules out conventional CD players, since they can decode & produce music data only.

I haven't seen a CD-I player come across my bench for years now. Either they're not being made any more or the technology has been encorporated into CD Rom drives.

06-03-1999, 12:59 AM
opus, I think I had one of those CD's in a CD-I format...It was a disc of instrumental movie themes from silents to current (great disc...wish it hadn't been swiped) but according to the liner notes there were also visuals that you could add to your home videos ("Coming Attractions" bumpers and whatnot.) I never even SAW a CD-I player that I can recall so needless to say I never got to enjoy that aspect of the disc.

06-03-1999, 08:33 AM
- - - Well nuts. I can't see the tracks now. I saw them last night (after dark) when the only light was a halogen desk lamp, but I can't make them out to measure them now in daylight. I guess I'll be posting an update about twelve hours from now. . . - MC

06-03-1999, 09:21 AM
The format used for multimedia music discs is usually called "CD Plus" by music companies but is a simple process called Multi-session writing in the computer world. a multi-session disk is similar to how a Kodak Photo CD works. You, most likely, will not fill up a whole CD at once with your pictures so you can return and add another CD burn session to the CD later.

With music they lay the music track first and they then create a second session with the multimedia computer content. Some CD ROM's cannot read multi session CD's?

Why you ask? Because CD ROM drives in computers use a marker at the beginning of the disk called the Volume Table of Contents (VTOC) to determine the contents of a disk. Some CD ROM's will not look for a second VTOC after they find the first so they will not see the multimedia content.

The best way to ensure you can read multisession CD's is to buy big name drives, NEC, Mistumi, Sony, etc. Avoid Goldstar drives at all costs.

To deal with men by force is as impractical as to deal with nature by persuasion.

06-03-1999, 10:48 AM
I'm guessing Charles has an "Enhanced CD" from my experience. According to the back, Enhanced CD is a certification mark of RIAA, whoever they are. I have a couple of them (the one I'm looking at is Sarah McLachlan's "Surfacing") and they have some QuickTime movies on them, the ability to play the CD from a graphical screen as opposed to whatever CD player program you use, and a few other odds and ends depending on the CD. Oddly enough, I never see the Enhanced CD function on the label of the CD ("Buy this CD and run the QuickTime movies!") but rather, it's always been some tiny icon on the back of the jewel case that you have to look for or randomly notice.

"I guess it is possible for one person to make a difference, although most of the time they probably shouldn't."

06-03-1999, 10:57 AM
Enhanced CD, CD Plus Music Plus it's all the same thing, they all just mean "multi session CD's"

To deal with men by force is as impractical as to deal with nature by persuasion.

06-03-1999, 01:35 PM
How about CD+G? I have one CD that has this feature, but never used it in anything that supported CD+G (my guess is it is long obsolete)..

06-03-1999, 01:48 PM
CD+G or CDG as it is also known is used or Karaoke CD's. This format uses special software to read the encoded format (rather than the hard wired decoders for CD plus or CD Enhanced).

You can still find software readers for this format and also order CD's in this format.

Two Software readers/encoders:
Disc Architect

To deal with men by force is as impractical as to deal with nature by persuasion.