DSP Robotics Support

I just found another piece, that could save (very little but some) CPU due to need of reusing pack/unpack on the go. How to convert this one into mono4 single ASM piece? (Multipliers are used instead of selectors/multiplexers to avoid code resets on switch; I guess this one is not doable in code due to different operations on channels?). Correct me if I'm wrong (i.e. if there is no benefit from such conversion).

This one only works with the first 2 channels of packed mono. The other 2 channels are overwritten, by a copy of the first 2.

Thanks!

Good learning tool for getting some basics on the go.