Editor is main role where he or she place proper graphics with sound effects and record the same and play and get the feedback from director and producer.
Explanation:
Normally editing the picture or video and remixing the video with sound are done by graphic designer, editor or sound engineer.
All three had do proper coordination to get proper output results
Graphic designer who makes the video or photo their color combinations and picture orientation.
Sound designed after the graphic mix been done sound engineer has play proper BGM and record sound.