Improve the DVS

Hi,

So we're at the version 6, and the DVS still can't compete with the standard industry:

I know master tempo is not recommended when scratching accurately (while Traktor can do it without any problem), but at least it should be Ok for classic baby scratch to launch a record for example.

On basic slow mouvements, I got digital artefacts. The sound I simply back and forth slowly are dubbed with the same sound played at a normal speed.

Sometimes, it drift a bit. Let's say I start a scratch at 12 o'clock, it can slightly moves around that position, usually after it.

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