Crossfader position jumps when Auto DJ disabled

[Jamie Gifford]

Disabling Auto DJ has the side-effect of centering the crossfader. This is deliberate but it's a surprising behaviour with a potentially nasty outcome - maybe I'm considering turning off the Auto DJ, so I run the cold deck through the headphones, decide "Yes, disable Auto DJ" but forget to stop the monitored deck running before I press "disable Auto DJ"...

[Daniel Schürmann (daschuer)]

You have hit a valid issue.
On the other hand the current behaviour is intended, it puts the crossfaded back to a position where it was probably before, to allow instantly Mixxx successor tracks using the line faders.This is especially important if a user has disabked the crossfader in skins or no mapping for it.

Both usecase are valid, so how can we combine both?

Would it help to not center the crissfader if a track is playing on the cold side.

Do you have an other idea to distinguish these use cases?

[Jamie Gifford (jamie.gifford)]

If a human operator would normally leave the crossfader in the centre, why not program the Auto DJ to also return the crossfader to the centre when he is not handling a track transition?

More generally, I guess there are two general ways to use the crossfader: either normally leave it in the centre, or normally leave it to the side. Currently the Auto DJ unconditionally works with the "normally to side" style. But Auto DJ could easily observe the initial crossfader position when he is enabled, and adopt one style or the other depending on whether it started out centered or to one side.

So the algorithm I am imagining is:

- On "Enable Auto DJ", examine the cross fader position. If it looks like it's to the side, then Auto DJ will operate in "side" style; if it looks like it's centred, then Auto DJ will operate in "centered" style

- "Side" style is the current style.

- "Centered" style is the same, except after the track transition and the cold deck stops running, Auto DJ recenters the crossfader; and before the next transition, if the cold deck is not already running, he moves the slider to the hot side in preparation for the crossfade. Or he could use the line faders instead of the crossfader if that is more idiomatic.

- On "Disable Auto DJ", nothing happens except the Auto DJ stops doing his thing.

- Likewise, on "Enable Auto DJ", he doesn't touch the faders at all, he just looks at how they are and gets ready for the next transition based on his observation.

So then "Disable Auto DJ" followed by "Enable Auto DJ", or "Enable Auto DJ" followed by "Disable Auto DJ" would be a no-op with no jumps in the crossfader in the middle.

[Daniel Schürmann (daschuer)]

This sounds a bit like to much magic for me.
How about start with a solution that just skips centring crissfader if it was on one side before Auto DJ was started?

Mmm.. this fails in my use case where I use AutoDj at the beginning of my set.

So we probably really need a preferences option. Odd.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/9262