- Nov 23, 2017
it is inaccurate and IMHO misleading to refer to upsampling as decompression. Upsampling does not decompress anything or add anything.
My experience is that upsampled audio sounds better, this is through Behringer Ultramatch and Ultracurve boxes, and is I suspect simply a function of the easier analog filtering offered by the higher rate. Without knowing the internals I cannot however be sure, perhaps it's a different effect.
Upsampling I view as decompression. Analog data has infinite points per second, but we only need X per second for any given max frequency as per Nyquist. What actually happens in the upsampling is that the software adds points in - in the case of 2x upsampling it calculates and adds points between the original ones (ideally not moving the original ones). I've programmed this stuff with convolutions - you end up with more (or less if you want!) points. This in my mind is adding something, it's not really extra data, it's simply calculating what would have been there if the sample rate was higher.
Upsampling is only really done for easier filtering in my view, we don't technically _need_ the extra points, but it helps if we add them in mathematically and then pass the result it through a simpler analog filter to recreate the infinite samples per second of Analog. Then because of the intermediate points each step is less in magnitude and a decent (non brick wall) filter can operate.
I hope that answers my view of the digitising and re-conversion back to analog as a form of compression -> store/streaming -> expansion.