If no custom matrix has been previously set or the AVAudioResampleContext is
not open, an error is returned.
@param avr audio resample context
@param matrix mixing coefficients; matrix[i + stride * o] is the weight of
input channel i in output channel o.
@param stride distance between adjacent input channels in the matrix array
@return 0 on success, negative AVERROR code on failure
Get the current channel mixing matrix.
If no custom matrix has been previously set or the AVAudioResampleContext is not open, an error is returned.
@param avr audio resample context @param matrix mixing coefficients; matrix[i + stride * o] is the weight of input channel i in output channel o. @param stride distance between adjacent input channels in the matrix array @return 0 on success, negative AVERROR code on failure