User Manual

Pro Tools Reference Guide64
The maximum available CPU Usage Limit de-
pends on the number of processors in your com-
puter and on the number of processors you spec-
ify for host processing. This value can range
from 85% for single-processor computers (ex-
cept for 003, 003 Rack+, 003 Rack, Digi 002, and
Digi 002 Rack, which have a limit of 99%), and
99% for multiprocessor computers (which dedi-
cate one entire processor to Pro Tools).
On multiprocessor computers, the maximum
CPU Usage Limit is reduced when you use all your
processors (as selected in the Host Processing
pop-up menu). For example, on dual-processors,
the limit is 90%. On four-processor computers,
the limit is 95%.
To change the CPU Usage Limit:
1 Choose Setup > Playback Engine.
2 From the CPU Usage Limit pop-up menu, select
the percentage of CPU processing you want to
allocate to Pro Tools.
3 Click OK.
Host Engine (Error Suppression)
The Host Engine options in the Playback Engine
determine error reporting during playback and
recording. This is especially useful when work-
ing with instrument plug-ins.
On Pro Tools|HD systems, there is a single Host
Engine option. On host-based Pro Tools systems,
there are two Host Engine options.
• Enable error suppression only if you are expe-
riencing frequent errors that are interrupting
your creative workflow. When error suppres-
sion is enabled, you can experience a degrada-
tion of audio quality. However, this may be
acceptable in order to avoid interrupting play-
back and recording when working with in-
strument plug-ins.
• Disable error suppression when you need to
ensure the highest possible audio quality,
such as for a final mix.
To enable error suppression:
1 Choose Setup > Playback Engine.
2 Select Ignore Errors During Playback/Record.
3 If available, you can also select Minimize Addi-
tional I/O Latency.
4 Click OK.
Error Suppression Options
Ignore Errors During Playback/Record When en-
abled, Pro Tools continues to play and record
even if the host processing requirements exceed
the selected CPU Usage Limit. This can result in
pops and clicks in the audio, but does not stop
the transport.
Minimize Additional I/O Latency (Host-based
Pro Tools Systems Only) When enabled, any ad-
ditional latency due to suppressing errors during
playback and record is minimized to 128 sam-
ples. Suppressing errors requires at least 128
samples of additional buffering on some sys-
tems. If this option is disabled, the buffer is half
the H/W Buffer Size, or at least 128 samples
(whichever is greater). If you are on an older,
slower computer, you may want to disable this
option to avoid adverse performance.
Increasing the CPU Usage Limit may slow
down screen responses on slower computers.