Vince Cimo

I'm developing an Ableton looper object but i'm having trouble syncing with the Ableton clock. Here's the issue:

Let's say you've recorded a loop which plays back x number of times, then stopped the loop playback; you want to re-trigger the loop but want to loop to start playing in time with the Ableton clock (which is running). You have quantize set to 1 bar and hit the play button 2.3 beats before the bar. The play() function then needs to delay that amount of time (related to the BPM) before calling the play operation.

This is seemingly really simple but unless my calculations are wrong there's a bit of jitter when the loop re-triggers. I've put together a dead simple patch to try and debug this issue, it has one button, which you can click after starting the Ableton clock and then it should output a midi note right on the beat. If you try it, you'll notice that it drifts....sometimes it's on, sometimes it's not. I've tried this with the Javascript task object, a Java MaxClock object and a Java TimerTask object....same issue.

Here's my basic calculations, i'm also attaching a demo project:

// number of beats until grid line = total number of beats on timeline - total beats on timeline rounded to int beat

double beatsTillGrid = (Math.floor(settings.getCurrentTime() / settings.getQuantize()) + 1 ) * settings.getQuantize() - settings.getCurrentTime();

//number of ms to delay start = (55.5 beats / .5 beats )

// 100 beats in a minute = 1.6667 beats per second = .00167 beats per millisecond

final double msTillGrid = beatsTillGrid / ( settings.getTempo() / 60000);

Thanks for any help you can give me! I'm guessing this has something to do with the threading or the bpm precision...hopefully I can figure it out.

Let's say you've recorded a loop which plays back x number of times, then stopped the loop playback; you want to re-trigger the loop but want to loop to start playing in time with the Ableton clock (which is running). You have quantize set to 1 bar and hit the play button 2.3 beats before the bar. The play() function then needs to delay that amount of time (related to the BPM) before calling the play operation. 

 log("attempting quantized play");
                // number of beats until grid line = total number of beats on timeline - total beats on timeline rounded to int beat
                double beatsTillGrid = (Math.floor(settings.getCurrentTime() / settings.getQuantize()) + 1 ) * settings.getQuantize() - settings.getCurrentTime();
                //number of ms to delay start = (55.5 beats / .5 beats )
                // 100 beats in a minute = 1.6667 beats per second = .00167 beats per millisecond
                final double msTillGrid = beatsTillGrid / ( settings.getTempo() / 60000);

Thanks for any help you can give me! I'm guessing this has something to do with the threading or the bpm precision...hopefully I can figure it out.


synchronizing-with-the-ableton-clock

I can't see what you're doing 'cause the JavaScript is missing (at least when I open it in the amxd~ object), but...

Rather than trying to calculate when the next downbeat is going to come, why not just wait for the next downbeat, and then trigger whatever you want to have happen? Here's an example of what I mean, in plain ol' Max, using a MIDI note as an example. Provide a note on the kslider, and it will be played on the next downbeat.

Synchronizing with the Ableton clock