User Manual

WAVELAB
21 – 578 Burning an audio CD
Red Book CD is not a real file format
Those of you who are computer literate might know about file formats.
Please note that Red Book CD is not a real file format. All the audio on the
CD is stored in one big chunk, one file if you will. This is different from
hard disks, for example, where each file is stored separately. Understand-
ing the fact that all the audio is in fact one long stream of digital data is
something that will probably help you better understand the limitations of
the format.
The different types of “events” on an audio CD
There are three types of events that can be used to specify various sec-
tions of audio on the CD. These are:
About frames, positions, small frames and bits
The data on an audio CD is divided into frames. A frame consists of 588
stereo samples. 75 frames make up one second of audio. Why? Well, 75
x 588 = 44100, and since the sampling frequency of the CD format is
44100kHz (samples per second), this equals one second of audio. When
you specify positions on the CD, in WaveLab, you do it in the format
mm:ss:ff, where mm is minutes, ss is seconds and ff is frames. The frame
values go from 0 to 74, since there are 75 frames to a second.
Technically, there is no way to specify something smaller than a frame on
a CD. One effect of this is that if the length of a track on the CD does not
equal a perfect number of frames, some blank audio must be added at the
end. Another effect of this is that when you play the CD, you can never lo-
cate (position) to anything closer than a frame. If you need some data in
the middle of a frame, you still have to read the whole frame. Again, this is
unlike a hard disk, where you can retrieve any byte on the disk, without
reading the surrounding data.
Event Description
Track Start There can be up to 99 tracks on one CD. Each is identified by its start
point only.
Track Sub-Indexes On advanced CD players, you might have noted that a track can be di-
vided into sub-indexes (sometimes called only indexes). These are used
to identify “important” positions within a track. There can be 98 sub-in-
dexes in each track. However, since it is difficult and time-consuming to
search for and locate to a sub-index, many CD players ignore this infor-
mation.
Pause A pause appears before each track. Pauses can be of variable lengths.
Some CD players indicate the pauses between tracks on their displays.