Smooth Animation Using .inPoint and .outPoint?

[LuTai14]

Hello Everyone!

I'm making an Audio Visualizer but I want to make it automatic since I will be using many different songs.

Basically, I want to make a circular stroke that keeps track of the progress of the song. In other words, the circle should not be present at the beginning of the song, it should build up as the song goes and complete the circumference when the song finishes.

 

As you can see from the picture (for better quality https://imgur.com/a/LtPiGng), I used a simple "Linear" expression where I used the inPoint of the song layer (which is actually a precomp) as starting time and the outPoint as the end time. What I have is

start = thisComp.layer("Song").inPoint
end   = thisComp.layer("Song").outPoint

linear(time, start, end, 100, 0)

And everything works fine.

However, the problem is that the bar does not proceed smoothly. As the video shows, the bar goes step by step.

Can anyone suggest a way of fixing that?

Thanks in advance

[Mike_Abbott · Accepted solution]

I think it's just an accuracy limitation with the stroke effect.
Use a shape layer - stroke only, with a trim paths modifier. Apply your expression to the trim path start or end value. That seems to work fine from a brief test.