User guide

CobraNet Programmer’s Reference

Audio Paths

the network receivers to the SSI outputs. Routing channel 0 is a special logical channel

used to supply silence to a transmitted channel or serve as a “bit bucket” when receiving

from the network.

Audio arrives and leaves the interface through the SSI receivers and transmitters. As

each sample arrives it is buffered. The mapping of audio input and output channels to

audio I/O buffer offsets is fixed (and non-intuitive). To accommodate channel numbering

differences of different CobraNet devices, the audioMap variables allow a mapping from

audio I/O buffer offsets to routing channel numbers. This mapping is preset by the

manufacturer and should never need to be altered.

4.2 Bundle Transmitters

A Transmitter is a logical entity within the CobraNet interface capable of transmitting one

bundle of up to 8 audio channels. Input audio routing channels (0, 1 through 32) are

mapped into Bundles associated with a particular transmitter via the txSubMap variables

associated with that transmitter. There are 8 txSubmap variables associated with each

transmitter, each of which can be set to a particular routing channel number. The first

txSubMap variable sets the routing channel that will be transmitted in the first audio

channel in the bundle. The second txSubmap variable selects the source for the second

audio channel to be transmitted in the bundle...and so on.

Audio resolution (sample size) and sample rate (48 kHz or 96 kHz) are determined by

other transmitter parameters discussed in this document.

4.3 Bundle Receivers

A Receiver is a logical entity within the CobraNet interface capable of receiving one

bundle of up to 8 audio channels. Output audio routing channels (0, 33 through 64) are

mapped from the receiver via the rxSubMap variables. There are 8 rxSubMap variables

associated with each receiver, each of which can be set to a particular routing channel

number. The first rxSubMap variable selects the routing channel that will receive the first

audio channel in the bundle. The second rxSubMap variable specifies mapping the

second audio channel in the bundle...and so on.

4.4 Loopback

The loopback object provides a means for the interface to transfer audio channels

internally. Loopback overcomes the limitation that a device cannot receive its own

transmission and also allows the audio I/O system to be tested locally.

The audioLoopSource and audioLoopDest variables control this feature.

4.5 Output Channel Duplication

The audio routing channel mapping facilities allow a single routing channel to be mapped

to any number of audio channels in any number of network transmitters (Bundles). It is,

however, not possible to direct an audio channel in a network receiver to multiple audio

routing channels for output through multiple SSI channels or ports.

Output channel duplication allows output routing channels to be copied to other output

routing channels. This feature is implemented as a separate set of “dup” paths controlled