This article is from the CD-Recordable FAQ, by Andy McFadden (email@example.com) with numerous contributions by others.
CD-R's have a pre-formed spiral track, and the sector addresses are
hard-coded into CD-R media, so there's no flexibility. Every disc holds a
predetermined amount of data.
Most discs rated at 74 or 80 minutes hold slightly more than that.
How much more depends on the brand of media, batch of media, and perhaps
even on the recorder used (see section (7-6) for more details on how much
a CD-R can hold). In some situations you can exceed the stated capacity
of the disc; see section (3-8-3) below.
Since CDs are written in a spiral, the amount of data you can get on
a disc is affected by how tightly spaced the "groove" is. A standard
Red Book audio CD or Yellow Book CD-ROM is designed to allow at most 74
minutes of data. By using a tighter track pitch on the spiral "groove"
on the glass master, manufacturers can get more data onto the disc.
In theory this could make it harder for some CD readers to use the discs.
See section (3-8-1) for notes on 80-minute discs, and (3-8-2) for 90-
and 99-minute blanks.
The easiest way to get more data onto a disc is not to try. For audio CDs,
you can leave off one or two tracks that you're not overly fond of. For
data CDs you may be able to drop some images or sample data. The most
common problem people encounter with data CDs is trying to copy them as a
collection of files rather than doing a bulk copy of the entire disc. See
also section (3-24).
One user suggested using the "speed up" function of Sound Forge or Cool
Edit to increase the speed of extracted WAV files by 3%. This supposedly
gives better results than resampling, and allows writing 77 minutes of
audio onto a 74-minute disc.
If you have a mono recording, you could double the length of a CD by
recording half the sound on the left track and half on the right. The
sound would be recorded as two monaural files, and then merged into a
single stereo file with a sound editor like Cool Edit. (With Cool Edit
96: load first mono file. Use "Convert Sample Type" to convert to
Stereo. Select the right track, and Delete Selection. Use Mix Paste to
load the right track from the second file, or just fire up a second copy of
Cool Edit with the other track, and use Copy and Paste commands.) The
person playing the CD back will need to use a "balance" knob to select the
left or right track. One issue with this method is that the track markers
apply to both tracks, so providing random access to specific sections can
If you're trying to copy a CD-ROM or VideoCD and running out of room, you
may have a different problem. See sections (3-24) and (4-25).
Incidentally, don't get confused when you discover you have 700MB of audio
extracted from a CD that only holds 650MB. Audio sectors use 2352 bytes
per sector, while standard CD-ROM data uses 2048 (the rest is for error
correction). You can put roughly 747MB of audio onto a disc that only
holds 650MB of data.