DigiDesign Pro Tools Reference Manual page 54

In most cases, the default settings for your sys-
tem provide optimum performance, but you
may want to adjust them to accommodate large
or processing-intensive Pro Tools sessions.
Hardware Buffer Size
The Hardware Buffer Size (H/W Buffer Size) con-
trols the size of the hardware cache used to han-
dle host-based tasks such as Real-Time Audio-
Suite (RTAS) plug-in processing.
Lower Hardware Buffer Size settings reduce
◆
monitoring latency, and are useful when you are
recording live input.
Higher Hardware Buffer Size settings allow for
◆
more audio processing and effects, and are use-
ful when you are mixing and using more RTAS
plug-ins.
In addition to causing slower screen re-
sponse and monitoring latency, higher
Hardware Buffer Size settings can affect the
accuracy of plug-in automation, mute data,
and timing for MIDI tracks.
To change the Hardware Buffer Size:
Choose Setup > Playback Engine.
1
From the H/W Buffer Size pop-up menu, select
2
the audio buffer size, in samples.
Click OK.
3
RTAS Processors
The RTAS Processors setting determines the
number of processors in your computer allo-
cated for RTAS (real-time plug-ins) plug-in pro-
cessing.
With computers that have multiple processors,
or that feature multi-core processing or hyper-
threading, this setting lets you enable multi-pro-
cessor support for RTAS processes. Used in com-
42 Pro Tools Reference Guide
bination with the CPU Usage Limit setting, the
RTAS Processors setting lets you control the way
RTAS processing and other Pro Tools tasks are
carried out by the system.
For example:
• For sessions with large numbers of RTAS plug-
ins you can allocate 2 or more processors to
RTAS and set a high CPU Usage Limit.
• In sessions with few RTAS plug-ins, you can al-
locate fewer processors to RTAS and set a low
CPU Usage Limit to leave more CPU resources
available for automation accuracy, screen re-
sponse, or video.
• Increase or decrease these settings to accom-
modate TDM/RTAS plug-in conversion.
TDM/RTAS conversion can be desirable dur-
ing recording, depending on the latencies,
voicing needs, and record-monitoring capa-
bilities of TDM and RTAS plug-ins.
• Depending on the importance of video and
overall screen response, and on the density of
automation being employed, different combi-
nations of RTAS Processing and CPU Usage
Limit settings may achieve the best results.
For example, to improve screen response in a
medium-sized session using a moderate num-
ber of RTAS plug-ins, try reducing the number
of RTAS processors but keep the CPU Usage
Limit set to the maximum (99%) on a single
processor system.
The System Usage window shows the combined
amount of RTAS processing occurring on all en-
abled processors with a single indicator, regard-
less of how many CPUs are in the system. If the
System Usage Window shows that you are at the
limit of available resources, increase the number
of RTAS processors and/or the CPU Usage Limit
setting. (For more information, see "System Us-
age" on page 59.)