Alesis MASTERLINK ML-9600, Reference Manual

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Chapter 8
38
A
LESIS
ML-9600 R
EFERENCE
M
ANUAL
Here's where it can become confusing: 96kHz/24-bit stereo audio has a play speed data rate of
576,000 bytes per second, so, using the same "2X" data rate to the CD, you have audio being recorded
to the CD at about 0.53 times play speed (a five-minute song will be recorded to the CD in about 9
minutes, 26 seconds). Observing the track time counter will again confirm this measurement. Data is
still being recorded at the same rate to the CD, but there is a
lot more data to record, and it appears
slow based upon the time counter. 650MB (74-minute) CD24 discs will hold a maximum of about 19
minutes of 96kHz/24-bit audio, and if you divide 19 minutes by 0.53, you see that a full CD24 disc
will record in about 36 minutes (which is about ½ of 74 minutes, correct for a 2X record speed).
The upshot of all this is that a full CD24 disc will record in about 36 minutes, regardless of the sample
rates and/or word lengths of the audio being recorded. However, the higher the resolution of the
audio, the slower the counter will appear to count. Do not adjust your TV; this is normal and
expected.
Table 6.3.1 lists CD24 recording times versus audio resolution for a 650MB (74 minute) CD-R.
CD Type Sample Rate Word
Length
Record Time
74-minute
(650MB) CD
Record Time
80-minute
(700MB) CD
Red Book 44.1kHz 16-bit 74 minutes 80 minutes
CD24 44.1kHz 16-bit 64.4 minutes 69.6 minutes
20-bit 42.9 minutes 46.4 minutes
24-bit 42.9 minutes 46.4 minutes
48.0 kHz 16-bit 59.2 minutes 64.0 minutes
20-bit 39.4 minutes 42.6 minutes
24-bit 39.4 minutes 42.6 minutes
88.2kHz 16-bit 32.2 minutes 34.8 minutes
20-bit 21.5 minutes 23.2 minutes
24-bit 21.5 minutes 23.2 minutes
96.0kHz 16-bit 29.6 minutes 32.0 minutes
20-bit 19.7 minutes 21.3 minutes
24-bit 19.7 minutes 21.3 minutes
Table 6.3.1
CD24 Recording Times vs. Resolution
Note that at 44.1kHz/16-bit resolution, a CD24 holds 63 minutes of audio, instead of the expected 74
minutes. The reason for this is that CD-ROM format discs (which CD24 discs are) contain more error
correction data than Red Book audio discs (because of the obvious need for data integrity when storing
computer data), and can therefore hold less audio data than a Red Book disc. However, because of this
extra error correction information, the audio data itself on a CD24 is therefore more robust and is less
likely to have errors in it due to disc scratches.
Also note that 20-bit and 24-bit audio have the same recording time available on CD24; this is due to
the AIFF file format specification. A 20-bit AIFF file actually orders its audio samples as 24-bit, and
pads the last four bits with zeros. Thus 20- and 24-bit files end up being the same size when saved in
AIFF format. However, 20-bit files on the MasterLink's internal hard disk are recorded in true 20-bit
fashion, so 20-bit recording will give you longer recording time on the hard disk as compared to 24-bit
recording.