Introducing Soundstructure Design Concepts; Understanding Device Inputs And Outputs - Polycom SoundStructure C16 Design Manual

Introducing SoundStructure Design
Concepts
Before creating designs for the SoundStructure devices, the concepts of physical channels, virtual
channels, and virtual channel groups are introduced. These concepts form the foundation of SoundStructure
audio designs. In addition, the concepts of defining control virtual channels and control array virtual
channels from the logic input and output pins are introduced.

Understanding Device Inputs and Outputs

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, requiring 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 multiple types of devices being used, and, of
course, the particular channel numbers to be affected by the command. This approach requires that the
designer manually configure the device identification for each device that is 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 or outputs are used from one design to the next, this requires changing the
control system code programming and spending additional time debugging and testing the new code to
ensure the new device identifications and channel numbers are used properly. Every change is costly and
is error prone, and can often delay the completion of the installation.
SoundStructure products have taken a different, and simpler, approach to labeling the inputs and outputs
when multiple devices are used together. SoundStructure products achieve this simplification through the
use of physical channels, virtual channels, and OBAM's intelligent linking scheme. As shown in the
Understanding Physical Channels section, physical channels are the actual input and outputs numbers for
a single device and this numbering is extended sequentially when multiple devices are used. Understanding
Virtual Channels extends this concept by creating a layer over physical channels that allows the physical
channels to be referenced by a user defined label, such as "Podium mic", rather than as a channel number.
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