DigiDesign Digidesign Pro Tools 8.0, Справочное руководство

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Chapter 43: Mixdown 971
Mastering
In the final mastering process, you might record
directly to disk, DAT, DVD, CD, stereo master-
ing recorder, or a multitrack recorder (for sur-
round mixes).
Once you have created a master of your session,
you can transfer it to a portable medium for du-
plication. You can transfer the master file to CD
or DAT to be used as a master for pressing com-
pact discs.
Mastering to a Digital Recorder
Although it is usually best to master sessions di-
rectly to hard disk, Pro Tools also lets you master
digitally, direct to any AES/EBU-equipped or
S/PDIF-equipped digital recorder such as a DAT
deck.
24-Bit Input and Output
Pro Tools|HD systems support full 24-bit audio
input and output signal paths, with 48-bit inter-
nal mixing and processing, providing an addi-
tional 16 bits of headroom at the top of a chan-
nel’s dynamic range, and 8 bits at the bottom.
You can exchange files with other 24-bit record-
ing systems without any bit-depth conversion
(as long as they are in a compatible file format).
Pro Tools LE systems support 24-bit input and
output, and uses 32-bit floating point mixing
and processing internally. You can exchange
files with other 24-bit recording systems with-
out any bit-depth conversion (as long as they
are in a compatible file format).
Mastering and Audio Compression
Although audio compression is often an indis-
pensable tool in analog recording, it can present
problems in the digital domain. If you compress
an input signal at a very high ratio, you create a
signal that contains a much higher overall
power level compared to its transients. By re-
cording a number of such signals at the highest
possible level on multiple tracks, you create a
scenario that is more likely to clip the mixed
output signal.
High-power compressed signals, when mixed
together, create an extremely high-level output.
This output may rise above the full-code level,
resulting in clipping.
To avoid this problem, watch the overall level of
your program material—use a meter on a Master
Fader, or use an external mastering deck’s
meters to help identify clipping. If you are mas-
tering to hard disk, avoid mixing full-code audio
signals together at unity or “0” level, as this in-
variably causes clipping.
Mastering and Error-Correcting Media
Random access media (such as hard disks, opti-
cal cartridges, Bernoulli cartridges or WORM
drives) can produce a true digital copy of your
data, because every bit value is maintained. Se-
quential media (such as DAT tapes) use error
correction schemes to fix the occasional bad
data that is received in a digital transfer. These
corrections are deviations from the actual data,
and with successive reproductions, represent a
subtle form of generation loss.
You can avoid this loss by creating and main-
taining masters on random-access digital media
(such as a hard drive) and transferring them to
sequential digital media (such as DAT tapes)
only as needed.