Add Slicer mode with visual feedback

[mixxxbot]

Reported by: Holzhaus
Date: 2019-05-13T19:51:31Z
Status: Confirmed
Importance: Wishlist
Launchpad Issue: lp1828886

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It would be nice to have a "Slicer Mode" similar to that found in Serato. An mapping for the DJ-202 that is currently in-development already implements it, but is missing visual feedback in the waveform display:

https://gist.github.com/upCASE/88fb258e85546092af18bc3ff924f752#file-roland_dj-202-scripts-js-L1225

Thus, it would be nice to have something like that in Mixxx natively.

More information about Serato's Slicer Mode:

• https://serato.com/latest/blog/18405/learn-sliceri
• https://serato.com/latest/blog/16357/the-slicer-uoeno

[whanake-music]

I would also like to see this feature added, as there are lots of controllers with a 'Slicer' pad mode that would benefit from being supported without janky ComponentsJS work-arounds.

[fwcd]

Would love to see a slicer mode too, though this is probably dependent on having downbeat detection (which includes questions like how to handle 3/4, 5/4, changing measures etc.):

• [POC] Beats: Add editing controls and show downbeats on scrolling waveforms #4489

[whanake-music]

Most slicer modes I've seen rely on multiples of 4 beats, even if the tracks themselves are not in 4/4 time signature. Maybe slicer mode could be implemented without downbeat detection for now? Obviously not for release, it would need to be a bit more reliable than that, but maybe as a POC? Where initiating slicer mode will just initiate it at the beat closest to the current playhead's position?

[hsn10]

I use slicer a lot.
You set slider to slice unit and multiplier for example:
I use 8 boxes of 1/4 bar (1 slice = 1 beat if song is 4/4).

For simplicity we can implement in mixxx slicer counting length in beats, not bars. I am not sure, do we detect already if song is 4/4, 6/4 or something else? if we detect just plain song bpm then do slicer in beats, not bars.