Traktor Kontrol S4 Mk3: issue with slow scratching

[ronso0]

Bug Description

I noticed that when scratching very slowly in one direction (also when trying to hold the wheel steady in order to set a hotcue), the play position makes tiny jumps forwards and backwards resulting in unexpectedly loud sound artifacts.

However, scratching sounds pretty smooth when doing similarly slow/small moves with the waveform or with my old, rather low-res wheel on the Reloop TerminalMix 2/4 (the mapping does no filtering/averaging).
Yes, there are artifacts, much louder, higher pitch than comparable moves with vinyl of course, but they are still more quiet than with the S4 mapping.

I saw the wheel also sends absolute position data which is not used for certain reasons.
Could that be used when the wheel moves slowly?

I'll compare with the mappings in 2.4 or 2.5

mixxx/res/controllers/Traktor-Kontrol-S4-MK3.js

Lines 2439 to 2474 in 8354c8e

	// The relative and absolute position inputs have the same resolution but direction
	// cannot be determined reliably with the absolute position because it is easily
	// possible to spin the wheel fast enough that it spins more than half a revolution
	// between input reports. So there is no need to process the absolution position
	// at all; the relative position is sufficient.
	this.wheelRelative = new Component({
	oldValue: null,
	deck: this,
	speed: 0,
	input: function(value, timestamp) {
	if (this.oldValue === null) {
	// This is to avoid the issue where the first time, we diff with 0, leading to the absolute value
	this.oldValue = [value, timestamp, 0];
	return;
	}
	let [oldValue, oldTimestamp, speed] = this.oldValue;
	if (timestamp < oldTimestamp) {
	oldTimestamp -= wheelRelativeMax;
	}
	let diff = value - oldValue;
	if (diff > wheelRelativeMax / 2) {
	oldValue += wheelRelativeMax;
	} else if (diff < -wheelRelativeMax / 2) {
	oldValue -= wheelRelativeMax;
	}
	const currentSpeed = (value - oldValue)/(timestamp - oldTimestamp);
	if ((currentSpeed <= 0) === (speed <= 0)) {
	speed = (speed + currentSpeed)/2;
	} else {
	speed = currentSpeed;
	}
	this.oldValue = [value, timestamp, speed];
	this.speed = wheelAbsoluteMax*speed*10;

Version

No response

OS

No response

[ronso0]

Furthermore if I rotate the wheel veeeery slowly in one direction I can move it quite a distance before anything happens.

I tried the old way in the S4 mapping an it's much smoother:

• enable scratching:

  if (touched) {
     engine.scratchEnable(this.deck.currentDeckNumber,
       2150, // matches LED position @33 1/3
       33+1/3,
       1.0/8,
       1.0/256);
  } else {
     engine.scratchDisable(this.deck.currentDeckNumber);
  }

• scratch: simply use diff for engine.scratchTick()

   case wheelModes.vinyl:
       if (this.deck.wheelTouch.touched || engine.getValue(this.group, "scratch2") !== 0) {
           engine.scratchTick(this.deck.currentDeckNumber, diff);
       } else {
           engine.setValue(this.group, "jog", this.speed);
       }
       break;

This is my temporary fix until someone more familiar with this will take a look 🤷

[ronso0]

This is the Zulip thread https://mixxx.zulipchat.com/#narrow/channel/113295-controller-mapping/topic/engine.2EscratchTick.28.29.20or.20setValue.28group.2C.20.22scratch2.22.2C.20speed.29.20.3F

and my fix #14004