I got information mx6ul framerate on 480 for different image
for framebuffer, 20.982, for x11, 20.838, for Wayland 18.421, this is theory data.
if you need to improve the quality, try to use the command as below:
$ gstreamer-launch-1.0 filesrc location=<cut video file> ! decodebin ! queue max-size-time=0 ! autovideosink sync=false
try to use atuovideosink