Setup guide

Appendix F: TDM Mixing and DSP Usage 101
DSP Allocation
Digital Signal Processing (or DSP) capability is
one of the most powerful elements of your sys-
tem. The DSP chips in your system provide the
real-time processing power for your TDM Mixer
and plug-ins. There is a limit, depending on
your system, to how many functions a single
DSP chip can power at once. This section con-
tains some guidelines for getting the most from
your available DSP capacity.
DSP Allocation Basics
As in the analog world, every send bus or output
mix that you use demands that a summing
mixer exist for that group. On an analog con-
sole, the number of these summing mixers is
fixed by the physical layout of the console. In
the Pro Tools mix environment, this number is
variable, and depends on the number of output
mixes or sends that you choose to create.
Pro Tools allocates DSP power as it is needed to
build the mixers for each session.
We describe certain mixing or signal processing
functions as “using one DSP” or “using two
DSPs.” This refers to the fact that there are 9 DSP
chips on each HD card.
Each chip on a card can only power a certain
number of processing functions. If you have a
single Pro Tools|HD card, and you create a big
enough TDM mixer and use enough sends or
plug-ins, you will eventually use up or “max
out” the DSP capacity of that card.
Mixing and DSP Usage
Pro Tools builds a TDM mixer every time a ses-
sion is opened. Note that the term “mixer chan-
nel” applies to audio tracks (total voiceable
tracks), Auxiliary Input tracks, and sends and re-
turns that use any of the 128 internal busses.
When you go beyond a certain number of mixer
channels, Pro Tools will use another DSP to cre-
ate additional mixer capacity.
Master Faders do not use additional DSP power.
DSP Manager
Pro Tools software includes the DSP Manager, a
software component that optimizes the use of
DSP capacity on Pro Tools|HD systems.
When you have an Pro Tools|HD card in your
system, if your current DSP usage is approaching
the capacity of the card, and you then try to add
a mixer channel or assign a plug-in, the DSP
Manager will automatically try to make room
for the new mixer or plug-in on the
Pro Tools|HD card. It does this by reallocating
the existing TDM mixers and plug-ins to use the
available DSP capacity on the Pro Tools|HD card
as efficiently as possible.