In case the samples are interleaved, in and out must point to an array with a single element pointing to a
block of interleaved samples.
If non-interleaved samples are used, in and out must point to an array with pointers to memory blocks, one for
each channel.
Perform channel mixing on in_data and write the result to out_data. in_data and out_data
need to be in format and layout.
| this | |
| samples |
number of samples |
| in |
input samples |
| out |
output samples |