How to implement sinc interpolation
&quot;So do I only use the sinc functions for the samples that are closest to my x value?&quot;
Yes, when you are truncating.
&quot;Is this what is meant by &quot;windowed sinc&quot;?&quot;
Yes.  The sinc goes to infinity, calculating that is impractical.
&quot;How many samples should I go in each direction away from my x value?&quot;
The sinc diminishes the further away you are.  At some point additional points become insignificant (no wider than a whisker on a gnat).
&quot;Additionally, my DAW has something called &quot;32 point sinc&quot; resampling. What is the &quot;32 point&quot; supposed to mean in this case?&quot;
I'm pretty sure it means a 32 point window, centered on your current sample.
Sinc interpolation is one form of interpolation.  It is the &quot;Fourier compatible&quot; one as it gives limits on a bandwidth basis.
Here is another link that may be even more useful:  Multi-channel audio upsampling interpolation
On re-reading this reference, Olli has already done this analysis, spectacularly.