User`s guide

Appendix B: TDM Mixing and DSP Usage 383
appendix b
TDM Mixing and DSP Usage
Pro Tools TDM Technology
(TDM Systems Only)
Digidesign’s TDM (or time division multi-
plexing) technology is based on the concept
of a single, high-speed data highway, or
bus. In Pro Tools 24 MIX/MIXplus,
Pro Tools 24 and Pro Tools III systems, in-
dividual channels from sources such as disk
tracks, sends, or busses are sent out from
Digidesign audio cards, and combined to-
gether or multiplexed onto the TDM bus. At
the receiving end, the audio cards can lis-
ten to any connection on the bus, and take
whatever data they need.
With Pro Tools 24 MIX/MIXplus,
Pro Tools 24 or Pro Tools III systems, you
can choose how to allocate the processing
power of your system. In most cases, you’ll
start the allocation process by configuring
your mixer, then assigning Plug-In effects
according to how much remaining process-
ing power you have.
DSP Allocation
(TDM Systems Only)
Digital Signal Processing (or DSP) capabil-
ity is one of the most powerful elements of
your Pro Tools 24 MIX/MIXplus,
Pro Tools 24 or Pro Tools III system. 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 contains some guidelines for get-
ting the most from your available DSP ca-
pacity.
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 console, the number of these sum-
ming mixers is fixed by the physical layout
of the console. In the Pro Tools mix envi-
ronment, this number is variable, and de-
pends 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.