Setup guide

Appendix F: TDM Mixing and DSP Usage 105
For example, creating a new Auxiliary Input
track and setting its input to bus 5 will create a
1x2 mixer for bus 5, even if no sources have
been created yet.
Submixing
When the number of channels that must be
mixed exceeds the capacity of a single DSP, ad-
ditional “main” mixers are created automati-
cally, along with summing submixers (which
sum together the “main” mixers). The use of
submixers allows large mix configurations to be
created.
For example, on a Pro Tools|HD system, when a
Stereo mixer running at 44.1 kHz needs to grow
to more than 68 inputs, a submixer is created
along with another “main mixer” that provides
“n” number of inputs beyond 68. Both the orig-
inal 68x2 mixer and the new “N x 2” mixer
which provides additional inputs are routed to a
submixer, and its outputs are finally sent to the
desired destination (such as Output 1–2 on your
main audio interface).
Note that any small delays (on the order of a few
samples) that are created remain equal between
these main mixers because they are summed to-
gether by means of submixers, and are not cas-
caded.
The total number of voiceable tracks supported
by your particular Pro Tools configuration will
ultimately determine the maximum number of
channels for your TDM mixer.
Mixers and DSP Hardware
Different mixer plug-ins are available, each of
which uses DSP power at slightly different rates
on the different audio cards (and their DSP
chips), as shown in the following tables.
In Pro Tools|HD systems, the number of avail-
able mixers per DSP chip is based on the type of
card and session sample rate.
See “Mixer Plug-ins” on page 108.
HD Accel (for PCI or PCIe) card, Standard mixers
Mixer
Sample Rate
(kHz)
Usage per Chip
Stereo 44.1 and 48 124x2
88.2 and 96 54x2
176.4 and 192 16x2
Surround, 5.1 44.1 and 48 46x6
88.2 and 96 34x6
176.4 and 192 8x6
Surround, 7.1 44.1 and 48 34x8
88.2 and 96 25x8
176.4 and 192 4x8
HD Accel card (for PCI or PCIe), Dithered mixers
Mixer
Sample Rate
(kHz)
Usage per Chip
Stereo
Dithered
44.1 and 48 113x2
88.2 and 96 54x2
176.4 and 192 16x2
Surround
Dithered, 5.1
44.1 and 48 44x6
88.2 and 96 27x6
176.4 and 192 8x6
Surround
Dithered, 7.1
44.1 and 48 34x8
88.2 and 96 20x8
176.4 and 192 4x8