Implementation of "hint_min_samplerate" and semi-piecewise interpolation

[PythonBlue]

This pull request implements optional voice oversampling via the ARIA-specific opcode "hint_min_samplerate".

Also implemented a custom interpolation mode that, when combined with said oversampling, can sound convincing to alias-free piecewise interpolation. To activate this interpolation, one needs to set the "sample_quality" to 0.

Third significant change was allowing the resonance to go as low as "-3" as I felt 0 sounded a little too sudden of a cutoff to me. This much can be ommitted from the main repo if necessary.

[jpcima]

Some quick remarks

• sample_quality 0 is not implemented. It's just a clause to add in Voice.cpp fillInterpolatedWithQuality with the quality kInterpolatorLinear. This would be good as a PR of its own. It will be a SFZ extension.
• I've got a feeling that the IIR technique would be inefficient at high rates. Perhaps at low rates we can depend on the half-band technique (as exists now);
  upper rates could use Polyphase FIR technique? then these frames that will be discarded by decimating can be skipped altogether, and also FIR is not autodepent of its output, which opens the possibilities of SIMD implementation

[jpcima]

Perhaps, this has to do with this method you are implementing?
https://www.gearslutz.com/board/electronic-music-instruments-and-electronic-music-production/750045-synclavier-emulation.html
https://www.gearslutz.com/board/showpost.php?p=8127446

[PythonBlue]

It does, yes, and it is the same premise. Basically, my method of interpolation is meant to get close to the desired sound of the imaging frequencies, while controlling the obvious aliasing that happens when said frequencies exceed the Nyquist.

[paulfd]

Do you mind if I extract the part about the cutoff curves in separate PRs?

[PythonBlue]

Do you mind if I extract the part about the cutoff curves in separate PRs?

Not at all. I should've updated this pull request anyway to say that "hint_min_samplerate" was eventually dropped in my fork due to the complexity of updating with the newer commits. Feel free to borrow and refine my code for the attack/decay/release_shape opcodes as well if you wish.