Creating a metro object using BPM

keykeeper

In Supercollider, Max Msp etc you will find a metro object that will trigger events at a certain rate based on BPM. Is there some built in functionality in Processing I can use for the same functionality. This needs to be 100% accurate so using draw() and frameRate will not be sufficient since it varies slightly. Alternatively does anyone have a suggestion on how this can be done?

jeremydouglass

1. There is no such thing as 100% accuracy.
2. You can get better accuracy from frameRate and the draw loop simply by running on faster hardware.
3. If you really, really need close to millisecond accuracy, there are ways to do it. See discussion and debates in this thread: Timing for draw loop. Briefly, tight loops will get you time-aligned, but they can stress your processor and cause interaction lag. Some alternatives are less precise, but also have fewer downsides.

keykeeper

Hi, thanks for the reply.

I did a simple test setting frameRate to 120 and printing the frameRate variable. Some of the output is shown below. As you can see it goes as high as 127,29.. and this is far to unaccurate in terms of making music. Therefore I need something more stable. I will review the other thread to see if I find a solution.

120.879265
119.83711
120.369385
120.872314
119.90422
120.26277
120.80755
119.867615
120.40936
120.59332
121.1965
120.27273
120.69504
119.70904
115.85873
125.79986
127.29039
125.85537
125.78165
124.242294
124.33107
124.44801

GoToLoop

• You can use thread() to create a Thread to run a function.
• Then you can have an infinite loop there, timed w/ delay().
• But you can't directly access the canvas. Use a separate PGraphics instead.

jeremydouglass

You might also be interested in Praxis -- I haven't tried it yet, but it is also a patch-based IDE, and it mentions "low-latency audio" as part of its design.

keykeeper

Thanks for the replies.

Praxis looks just like what I need and I am so glad you informed me jeremydouglass. I am working with audio and visuals but I have never come across Praxis(!) and I can't wait to explore the software - thanks!

neilcsmith_net

@keykeeper yes, if you're doing audio and visuals together, come try out Praxis LIVE, and give me a shout if you need any help. I've not exactly been uncritical of Processing for audio! Praxis LIVE's architecture has a better approach for this.

There are two issues with your approach if you're wanting accurate audio BPM without jitter. Firstly, you need to sync audio triggering to the soundcard clock, not the system clock - they'll drift! Secondly, you need to trigger things in the audio thread itself - triggering things from draw() or a background thread is useless.