channelMap
An array of integers that indicates which input to derive each output from.
Declaration
var channelMap: [NSNumber] { get set }Discussion
The array size equals the number of output channels. Each element’s value is the input channel number, starting with zero, that the framework copies to that output.
A negative value means that the output channel doesn’t have a source and is silent.
Setting a channel map overrides channel mapping due to any channel layouts in the input and output formats that you supply.