Add a MixxxControl (ControlObject) that fires on each beat

Here's a workaround for now. Albert said:
"The beat ticks always start right at the start of the track, and you know the BPM, so based on the playback position and the BPM, you should be able to trigger something."

So you have duration in seconds, and doing 60/bpm = seconds per beat. So when (visual_playposition * duration) modulus (60/bpm[/24 for MIDI clock pulses]) == 0, you're on a beat and should light your LED. Be sure to use engine.connectControl() to connect the "[ChannelN],rate" MixxxControl to a script function that stops & restarts the timer with the new BPM value (obtained with "[ChannelN],rate" x "[ChannelN],bpm",) so it's updated when the pitch control is moved.

This functionality should be added to the common script functions file so script writers don't need to worry about these gory details, but there's currently no way for a slot function to find out what group the changed MixxxControl was (it can't find out which deck fired the signal at the moment) so it's impossible to make a generic function set.

New CO ([ChannelN], beat_on) added on my branch. Midi clock needs a more involved design, something related to master BPM(fire events at known rate lower than latency, if that is even possible, and such)

Thanks for the patch, vininim -- just a few quick things to fix:

- As I mentioned in the channel, I think CachingReader shouldn't be passed into EngineControl's via their constructor. Rather, I think that EngineControl should get an onTrackLoaded method added to its interface, and the EngineBuffer should call that whenever a track is loaded for every EngineControl.

- In slotTrackLoaded, check that tio is not null, (for example, an eject will trigger that call with a null track). You should also clear the on_beat control when a track is loaded.

- In slotTrackLoaded, check whether a previous track is loaded, and if so, disconnect its beatsUpdated signal from your slotBeatsUpdated slot, that way changes to the beats of previously loaded tracks won't fire your slot.

- Don't include cmath or use std::fabs, just call fabs() -- you may need to #include "defs.h"

- Since the ClockControl isn't used anywhere in EngineBuffer, please don't add a member variable to EngineBuffer. Just call addControl on it when you create it.

Thanks,
RJ

Diff against main branch with fixes

Thanks for the patch vininim -- I committed it to trunk w/ some modifications. What name should I put you under in the credits?

Vinícius Dias dos Santos (can drop the acute accent)

Added, thanks!

On Tue, Mar 29, 2011 at 5:26 AM, vininim <email address hidden> wrote:

> Vinícius Dias dos Santos (can drop the acute accent)
>
> --
> You received this bug notification because you are subscribed to Mixxx.
> https://bugs.launchpad.net/bugs/604384
>
> Title:
> Add a MixxxControl (ControlObject) that fires on each beat
>

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/5454