I have a some questions concerning single instruction multiple data (SIMD). I heard that I only can use SIMD, if I do the same operations on two channels simultaneous. For example filtering the right and left channels of an audio signal simultaneous. Otherwise I found only library functions for a single channel e.g. FIR-filter, but these functions are already optimized for SIMD.
Is it generally better to process (filter) multiple channels simultaneous or sequential. Can I use SIMD, if I call 2 library functions which do not use SIMD (e.g. fir_interp).