Specifications

Chapter 2: Working with Real-Time Plug-Ins 9
CPU Usage Limit
The CPU Usage Limit controls the percentage of
CPU resources allocated to Pro Tools host pro-
cessing tasks. The default CPU Usage Limit set-
ting is 40 percent.
On single-processor computers, the maximum
CPU Usage Limit is 85 percent. On dual-proces-
sor computers, the maximum CPU usage limit is
99 percent.
◆ Lower CPU Usage Limit settings limit the ef-
fect of Pro Tools processing on other CPU-inten-
sive tasks, such as screen redraws, and are useful
when you are experiencing slow system re-
sponse, or when running other applications at
the same time as Pro Tools.
◆ Higher CPU Usage Limit settings allocate
more processing power to Pro Tools, and are
useful for playing back large sessions or using
more real-time plug-ins.
To change the CPU Usage Limit:
1 Choose Setups > Playback Engine.
2 From the CPU Usage Limit pop-up menu, se-
lect the percentage of CPU processing you want
to allocate to Pro Tools.
3 Click OK.
Delay in Digital Signal
Processing
(TDM Plug-Ins Only)
DSP processing in digital audio systems incurs
signal delay of varying amounts. Such delays
can vary from as short as few samples to as long
as several hundred samples, depending on the
type of processing applied.
If you have recorded an instrument on multiple
tracks using multiple microphones (a drum kit
for example) and process the different tracks
with different TDM plug-ins, the tracks may go
out of phase. You will then need to compensate
for these delays to avoid phase correlation prob-
lems.
Compensating with TimeAdjuster
You can compensate for TDM plug-in-induced
delays by using the TimeAdjuster plug-in. This
plug-in allows you to apply a specific number of
samples of delay to the signal path of a Pro Tools
track. TimeAdjuster provides settings files that
apply the correct compensation time in samples
for delay introduced by one or more plug-ins.
See the DigiRack Guide for information about the
Time Adjuster plug-in.
Increasing the CPU Usage Limit may slow
down screen responses on slower computers.
Choosing the CPU Usage Limit
For more information on the Hardware
Buffer Size and CPU Usage Limit parame-
ters, see the
Pro Tools Reference Guide.
See Appendix B, “DSP Delays Incurred by
TDM Plug-Ins” for information on delays
inherent in specific DigiRack TDM plug-
ins. See also the
Pro Tools Reference Guide
for a guide to calculating DSP-induced de-
lays.