DigiDesign Pro Tools 8.0 Reference Manual page 978

Dithering
Dither can significantly improve audio quality
when reducing the bit depth of digital audio.
When to Use a Dither Plug-in
You should use a dither plug-in in any situation
where you are reducing bit depth, for example,
when mixing down to a 16-bit file with the
Bounce to Disk command, or when sending
your final mix to an external digital device that
records at 16-bit resolution.
A dither plug-in is necessary even when mixing
down to 16-bit from a 16-bit session. Even
though 16-bit sessions use 16-bit files, they are
still processed at higher internal bit depths.
• Pro Tools|HD systems use 24-bit audio input
and output signal paths, and internal 48-bit
mixing and processing
• Pro Tools LE and M-Powered systems use 24-
bit audio input and output signal paths, and
internal 32-bit floating point processing for
mixing and audio processing
For this reason, whether you are working with a
24-bit session or a 16-bit session, the following
are recommended:
• When mixing down to a 16-bit destination,
use a dither plug-in on the main output.
• When bus recording a submix to a track in the
same session, do not use a dither plug-in on
the destination track.
• When mixing down to a 24-bit destination,
do not use a dither plug-in on the main
output.
• When mixing down to an analog destination
with any 24-bit capable interface, do not use a
dither plug-in on the main output.
• During normal recording and playback, by-
pass any dither plug-in on the main output.
960 Pro Tools Reference Guide
Bounce to Disk
Bouncing to disk does not apply dither when re-
ducing bit depth. To apply dither when bounc-
ing to disk, you should insert a dither plug-in as
the last processor in the signal path on a Master
Fader assigned to the bounce source audio out-
put path.
Using a dither plug-in on a Master Fader is pref-
erable to an Auxiliary Input because Master
Fader inserts are post-fader. As a post-fader in-
sert, the dither plug-in can process changes in
Master Fader level.
If you do not use a dither plug-in on your
bounce source path, and you choose to convert
to a lower resolution during or after bouncing to
disk, the resulting file will be converted by trun-
cation.
Using Dither on an Output Mix
Pro Tools includes real-time dither plug-ins that
improve 16-, 18-, or 20-bit performance and re-
duce quantization artifacts when reducing the
bit depth of an output mix.
To use a dither plug-in on an output mix:
Choose Track > New and create a (stereo) Mas-
1
ter Fader track.
Set the output of the Master Fader to the out-
2
put or bus path you want to bounce.
Assign the outputs of all audio tracks in the
3
session to the same path you selected in step 2.
The Master Fader now controls the output levels
of all tracks routed to it.
On the Master Fader, insert a dither plug-in as
4
the last processor in the signal chain.
In the dither plug-in window, choose an out-
5
put Bit Resolution and Noise Shaping setting.