Handbook for Sound Engineers

984 Chapter 25

25.24.3 DAW Audio Ins and Outs

Means of moving audio around are covered in more
detail in Section 25.25. DAWs just like any other
console need to get audio in and out, and from the lesser
to the greater this can include:

• PC’s built-in sound card. (It had to be mentioned, and
  besides, who honestly has never used one in a
  pinch?) Typically analog-in, analog-out (sometimes
  S/Pdif), at very low domestic signal levels, and of
  generally indifferent to awful quality. But convenient.


• USB/Firewire. Links to external sound card
  convertor boxes from stereo in/out up to as many as
  16 in/out, see Fig.25-152.


• ADAT. 8-in or 8-out via fiber-optic cable.


• MADI. Up to 64 ins or outs via coax.


• Ethernet. Either true TCP/IP Ethernet or audio-
  specific UDP variants using the same hardware typi-
  cally 64 I/O for UDP.

Specific drivers—and in the case of ethernet and
variants whole suites of interface code—need to be
installed on the PC to deal with the audio on these
various schemes. The DAW software has both input and
output routers that can pick which incoming sample
within a stream goes to what input, thus track, and
which DAW output gets sent out what slot.
So far, the PC-based, sequencer-modeled audio
control approach looks like a multitrack recorder (of
virtually unlimited scope) with wicked automation and
editing. But what of console-style audio processing?

25.24.4 DAW Internal Audio Paths

The audio routing within a DAW tends by design to be
quite basic: Fig. 25-152 shows this as being essentially
a route from input to a recorder track, thence from either
before or after the track to a mix bus (or buses), thence
to an output(s). Recognizable console like features such

as a fader and panning are included just to show a

typical starting environment.

What all the Xs mean is that it is possible to “drop in

a plug-in” (translated: apply an instance of a

signal-processing software module) or apply the signal

at that point to anywhere else there’s an X. An output

bus, for example, can and frequently does get routed

back to be a recording track source (bouncing in

oldspeak); many modules may be inserted concatenat-

edly at each X. There is considerable flexibility. This

approach—nearly everywhere being an insert point and

only providing access for processing—as opposed to the

“everything’s in there in case” traditional console model

allows what processing power there may be to be

applied as and where it is needed while leaving all other

paths unfettered.

25.24.5 Plug-Ins

A plug In is a collection, library, of disparate software

programs that variously (a) actually process (or

generate) the audio in some form or other—e.g. EQ,

dynamics, delay, reverb, etc., or a MIDI musical instru-

ment; (b) provide a graphical module for display on the

system’s GUI, replete with knobs, buttons, dials,

gauges, meters, and blinky-lights, (c) calculate the

conversion of the parameters from those controls into

coefficients that the actual signal processing can under-

stand; and a render metering data in the reverse direc-

tion, from audio to GUI. All the “handles” typically

become available to the system’s automation system,

either directly or by being MIDI addressable—in other

words, the module can look to the system as just yet

another MIDI slave device, which can automate it

accordingly.

Standards have evolved (in the form of requirements

by major DAW players) for plug-ins; VST (virtual studio

Figure 25-152. Simplistic DAW audio path.

Record

Play

etc.

Input router

Incoming

audio

stream

Recorder

track

Mix buses Outgoing

audio

stream

Output router

Fader