Yes, you need to check path to ffmpeg in inc/header.inc.php and change path to another ffmpeg binary which can process specified mp4 file without errors.
Thank you so much for the response. Can you kindly explain to me how to "change path to another ffmpeg binary"?
My current path in inc/header.inc.php as this:
define('BX_SYSTEM_FFMPEG', '/var/www/scrubdin.net/plugins/ffmpeg/ffmpeg.exe'); ///< path to ffmpeg binary