Using native size for video stimuli

I’m using the following code to create MovieStim objects:

S1 = visual.MovieStim(win, movie,
                      size=None,  # set as `None` to use the native video size
                      # pos specifies the /center/ of the movie stim location
                      pos=[0, 0],
                      flipVert=False,  # flip the video picture vertically
                      flipHoriz=False,  # flip the video picture horizontally
                      loop=False,  # replay the video when it reaches the end
                      autoStart=True, # start the video automatically when first drawn
                      units='pix') ```

But the video still looks deformed, not like in player.

If you put your movie in a movie component in builder, with no value in the size field - does that look as expected? if so have a look at the code compiled from that to cross check .