Hello,
Since I'm working on a project where having stable points is very important I think I'm concerned. I didn't use MediaPipe very much but before using it, I tried OpenPose, and I could tell that MediaPipe landmarks, at least compared to OpenPose, are very stable. Have you tried changing models' parametres ? You could apply smoothness to the model with
smooth_landmarks parameter. Also, have you tried changing other parametres? like changing the models' complexity, because using the lite version will give less accurate results.
You have also asked about if it's possible to give landmarks for every second instead of giving them in milliseconds. I will reformulate this, imagine a model where you inputs a video with more than 30fps and it outputs a single frame per second video ! that's how it would look like in your case, and some of human actions don't even take more than a second so you will actually perceive nothing from the motion.
Diaeddin BOUIDAINE