DigiDesign Pro Tools, Справочное руководство

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Pro Tools Reference Guide 660
MIDI and Audio Processing Plug-ins
Some audio processing plug-ins (such as Bruno
and Reso) and many instrument plug-ins let you
process audio while allowing MIDI data to con-
trol processing parameters. When you record
enable a MIDI or Instrument track that is con-
trolling an audio processing plug-in, the track
the plug-in is inserted on will go into low-la-
tency mode, effectively making the processed
audio play early.
To keep audio time-aligned when recording using a
MIDI controlled plug-in on an audio track:
■
Start-Control-click (Windows) or Command-
Control-click (Mac) the Track Compensation in-
dicator for the audio track to apply Delay Com-
pensation.
To keep audio time-aligned when recording using a
MIDI controlled plug-in on an Auxiliary Input:
1
Start-Control-click (Windows) or Command-
Control-click (Mac) the Track Compensation in-
dicator for the Auxiliary Input to bypass Delay
Compensation.
2
Enter the total system delay into the User Off-
set field.
Dither
Dither is a special form of randomized noise
used to mask quantization noise in digital audio
systems. Digital audio’s poorest distortion per-
formance exists at the lowest end of the dy-
namic range, where quantization distortion can
occur. Dither reduces quantizing errors by intro-
ducing very low-level random noise, thereby
minimizing distortion artifacts as audio reaches
low level. With dither there is a trade-off be-
tween signal-to-noise performance and less-ap-
parent distortion. Proper use of dither lets you
squeeze better subjective performance out of a
16-bit data format (such as Red Book compact
discs).
Pro Tools|HD systems process all audio inter-
nally at 24-bit, and Pro Tools LE processes inter-
nally at 32-bit, floating. Without dither to pro-
cess the 24-bit data to 16-bit, the extra 8 bits are
truncated (dropped entirely) when written to
media or a device with a 16-bit maximum (such
as CD recorders, and many DAT machines).
Dithering, on the other hand, preserves low-
level (quiet) fidelity in a surprising way—by
adding a small amount of noise to a signal.