Soundstructure Design Concepts; Introduction - Polycom SoundStructure C16 Design Manual

SoundStructure Design Concepts

Introduction

Before creating designs for the SoundStructure devices, the concepts of physi-
cal channels, virtual channels, and virtual channel groups will be introduced.
These concepts form the foundation of SoundStructure audio designs. In addi-
tion, the concepts of defining control virtual channels and control array virtual
channels from the logic input and output pins will be introduced.
All audio devices have inputs and outputs that are used to connect to other
devices such as microphones and audio amplifiers. These inputs and outputs
are labeled on the front or rear-panel (depending on the product) with specific
channel numbers, such as inputs 1, 2, 3, etc., and these labels refer to particular
inputs or outputs on the device. For instance, it is common to connect to input
"1" or output "3" of an audio device. This naming convention works well --
meaning that it provides a unique identifier, or name, for each input and
output -- as long as only a single device is used. As soon as a second device is
added, input "1" no longer uniquely identifies an input since there are now
two input "1" 's if a system is made from two devices.
Traditionally, to uniquely identify which input "1" is meant, there's additional
information required such as a device identification name or number, requir-
ing the user to specify input "1" on device 1 or input "1" on device 2 in order
to uniquely identify that particular input or output. This device identification
is also required when sending commands to a collection of devices to ensure
the command affects the proper input or output signal on the desired device.
As an example, consider what must happen when a control system is asked to
mute input 1 on device 1. The control system code needs to know how to
access that particular input on that particular device. To accommodate this
approach, most audio systems have an API command structure that requires
specifying the particular device, perhaps even a device type if there are multi-
ple types of devices being used, and, of course, the particular channel numbers
to be affected by the command. This approach requires that the designer man-
ually configure the device identification for each device that will be used and
take extra care to ensure that commands are referencing that exact input or
output signal. If device identification numbers are changed or different inputs
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