How to slow down ProRes file from 25fps to 16fps without re-encoding?
I just found a way to do this by changing the parameters help by fps tbr tbn tbc; answer is derived from this post.

ffmpeg -y -i at25fps.mov -c:v copy -video_track_timescale 16 at16fps.mov

I am getting these remarks from Apple Sound Media Handler (so I am not sure if this is the best way to do it)


  Non-monotonous DTS in output stream 0:0; previous: 0, current: 0; changing to 1. This may result in incorrect timestamps in the output file.
  
  Non-monotonous DTS in output stream 0:0; previous: 1, current: 1; changing to 2. This may result in incorrect timestamps in the output file.
  
  ...