I work in 2D animation and have to track effects to a lot of animation drawn at 12fps. I use the posterizeTime expression very frequently, but have been running into an issue where the value changes on the alternate frame from the handdrawn animation, creating an unpleasant strobing effect. I've tried linking the posterizeTime expression to sliders and keying when I need it to be at 12fps, but that does not change which frames the animation occurs on. How can I control the interpolation so that the value changes happen on the alternate frames from the ones they're currently on?
This might work (untested). The idea is that one frame is added to the posterization if the checkbox in ticked and nothing is added if its unchecked. So you would create a checkbox on this layer (or a central control layer) and pick whip the checkbox value where indicated. I'm assuming you're working at 24 fps.
t = (Math.round(time*12+pick-whip-checkbox-state-here))/12;