Accurate Metronome

succulentim

Call me crazy but I decided I wanted to try finally solving the issue of syncing animation to music in Scratch!

The issue is that every script takes time to happen, and so if you tell Scratch to wait a fraction of a second before doing the animation, it will wait that fraction of a second plus the extra time it took to run. Over time this builds up and the animation goes out of sync.

A solution to this kind of issue (that I learned from a youtube video about building a drum machine in excel) is to use the time from your computer (or, in Scratch, I've been trying to use the timer) to have a steady flow of time to schedule the animations to. Instead of something like

wait (0.3) secs
next costume

we have something more like

wait until <(timer)=((timer) + ((BPM) / (60)))>
next costume

(BPM stands for beats per minute, a measure of tempo. Divided by 60, we get beats per second.)

This way the costume will change on the beat exactly when we want it to.

However, in the project I was making trying to put this into practice, it hasn't been working. I'll post the wip so that hopefully anyone willing to help or give it a go can tinker with it. I'm not very good at math so that might be a problem, but I think the roadblock I'm running into might be due to the timer moving too fast for Scratch to pick up on it?

Either way, if anyone has any ideas or suggestions on how to make this work, or can point out any mistakes I'm making, I'd really appreciate it! Thank you!

Last edited by succulentim (Jan. 9, 2020 02:30:38)

nolbarry

A couple issues that I've noticed:
For starters:

<(timer)=((timer) + ((BPM) / (60)))>

This will never evaluate to true: timer cannot both be itself and a value slightly more than itself.
Also, you should use 60 / BPM instead of BPM / 60 to get the number of seconds between each beat.

My solution resets the timer each “frame” and then plays the next frame when the timer passes the length of a single beat:

forever
reset timer
wait until <(timer) > ((60) / (BPM))>
next frame :: custom
end

Last edited by nolbarry (Jan. 9, 2020 06:42:57)

succulentim

nolbarry wrote:
A couple issues that I've noticed:
For starters:
<(timer)=((timer) + ((BPM) / (60)))>
This will never evaluate to true: timer cannot both be itself and a value slightly more than itself.
Also, you should use 60 / BPM instead of BPM / 60 to get the number of seconds between each beat.

My solution resets the timer each “frame” and then plays the next frame when the timer passes the length of a single beat:
forever
reset timer
wait until <(timer) > ((60) / (BPM))>
next frame :: custom
end

thank you so much! this helped a ton!

succulentim

this is the updated link to the project

nolbarry

I think my using the “reset timer” block is offsetting it a little bit.
Instead of resetting the timer, try using a variable.

reset timer
set [nextBeatTime v] to (0)
forever
change [nextBeatTime v] by ((60) / (BPM))
wait until <(timer) > (nextBeatTime)>
next frame :: custom
end

This way, your beat variable remains totally independent of the loop waiting time.

Last edited by nolbarry (Jan. 10, 2020 19:46:13)

succulentim

nolbarry wrote:
I think my using the “reset timer” block is offsetting it a little bit.
Instead of resetting the timer, try using a variable.
reset timer
set [nextBeatTime v] to (0)
forever
change [nextBeatTime v] by ((60) / (BPM))
wait until <(timer) > (nextBeatTime)>
next frame :: custom
end
This way, your beat variable remains totally independent of the loop waiting time.

thank you so much, it works great now!! it no longer needs to be in turbo mode to work, and i could add back in the graphic effects that were causing program-breaking lag. thank you for the help, i learned a lot from it!

this thread is now resolved! (sorry, i can't edit the first post yet, haha)

Last edited by succulentim (Jan. 11, 2020 22:04:22)

jugobmix

wait (1) secs

3DemonGamer37

The Scratch Wiki really needs a metronome tutorial page, but I don't have an account, and by the time I set it up, some dude'll beat me to it.

BigNate469

3DemonGamer37 wrote:
The Scratch Wiki really needs a metronome tutorial page, but I don't have an account, and by the time I set it up, some dude'll beat me to it.

Please don't necropost. This topic is over 4 years old, and the OP seems to have gotten what they wanted.

Last edited by BigNate469 (March 29, 2024 00:09:26)

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