reduce number of sent midi messages for wheel leds

[goddisignz]

I had the problem that the rate that midi messages are sent to the controller apparently exceeds the maximum when the audio buffer size is set lower than 10ms. It was caused by the "playposition" control that in the ddj-sx controller script updates the position of the wheel leds inside the jog wheel. Apparently, when the buffer size is reduced, the number of position updates increases.

What happens than can be seen in the following video. All controls react in a delayed behavior as soon as two decks are playing and updating the wheel leds.
https://projects.goddi.ddnss.eu/wp-content/uploads/delayed_behavior.mkv

Therefore, I adapted the DDJ-SX script such that a midi message is only sent when the position of the wheel leds is really changed. Thanks to @JosepMaJAZ who pointed me towards the cause of the problem and the solution.

[Be-ing]

Again, please rebase this on the 2.2 branch.

[goddisignz]

Oh sorry, I didn't get your comment the first time. I was just confused where all these commits come from and thought I just made a mistake in the PR. Will do.

[Holzhaus]

@goddisignz In case you're not fluent in git, just do the following:

# First add the "upstream" remote and make sure you have the latest state of it
$ git remote add upstream https://github.com/mixxxdj/mixxx.git
$ git fetch upstream
# Then rebase on the "2.2" branch
$ git rebase -i upstream/2.2

The last command will open an editor window which shows all commits since 2.2. Delete all lines that do not belong to your PR. Basically, keep only the line that says pick ae98a4b reduce number of sent midi messages for wheel leds. If you're using vim, just type :%g!/ae98a4b/d to delete all lines not containing the string ae98a4b, hit enter and save and exit the file using :wq. Then force-push your branch:

$ git push -f origin ddj-sx-reduce-messages

[goddisignz]

Thanks @Holzhaus. I did rebasing before but never to a different branch.

[Be-ing]

Thank you!