User Manual

Pro Tools Reference Guide62
You can configure the Input and Output op-
tions for Pro Tools Aggregate I/O in the Mac Au-
dio Setup, which can be accessed from the
Pro Tools Hardware Setup.
Hardware Buffer Size
The Hardware Buffer Size (H/W Buffer Size) in the
Playback Engine controls the size of the buffer
used to handle host processing tasks such as pro-
cessing with Real-Time AudioSuite™ (RTAS)
plug-ins.
• Lower Hardware Buffer Size settings are useful
for improving latency issues in certain record-
ing situations or for improving certain system
performance problems:
• On all Pro Tools systems, lower settings re-
duce RTAS MIDI-to-audio latency (such as
when playing an RTAS virtual instrument
live and monitoring the instrument’s out-
put). Lower settings can also improve
screen response or the accuracy of plug-in
and mute automation data.
• On host-based Pro Tools systems, lower set-
tings reduce all input-to-output monitor-
ing latency on any record-armed tracks or
Auxiliary Input tracks with live inputs.
• On Pro Tools|HD systems, lower settings re-
duce monitoring latency that occurs on
tracks that have one or more RTAS plug-ins.
Lower settings can also improve the accu-
racy of MIDI track timing on systems with-
out a MIDI interface that supports time
stamping. Lower settings also improve
MIDI track timing on tracks using MIDI
virtual instruments that do not support
time stamping.
• Higher Hardware Buffer Size settings are use-
ful for sessions that are using more RTAS plug-
ins for playback. These settings allow for more
audio processing. They can also be useful to
reduce errors on machines that require a
higher buffer size.
To change the Hardware Buffer Size:
1 Choose Setup > Playback Engine.
2 From the H/W Buffer Size pop-up menu, select
the audio buffer size, in samples.
3 Click OK.
Host Processors
The Host Processors setting in the Playback En-
gine determines the number of processors in
your computer allocated for RTAS (Real-Time
AudioSuite) plug-in processing and other host
processing tasks.
With computers that have multiple processors,
or that feature multi-core processing or hyper-
threading, this setting lets you enable multipro-
cessor support for host processing tasks. Used in
combination with the CPU Usage Limit setting,
the Host Processors setting lets you control the
way host-processing tasks are handled by the
system.
If you need simultaneous input (recording)
and output (playback and monitoring) with
Pro Tools using the built-in audio options
on Mac, use the Pro Tools Aggregate I/O op-
tion. If you only need to playback audio for
editing and mixing, select the appropriate
built-in audio output option.