If you have the original source file and the “converted” version, compare them. If you only have the converted file and it’s broken, you may need to it properly.
ffmpeg -i sone385.mkv -ss 120 -t 2 -c:v libx265 -crf 20 -preset medium -x265-params "aq-mode=3:no-sao=1" -c:a libopus -b:a 64k -movflags +faststart sone385_better_2sec.mp4 sone385engsub convert020002 min better
On the Intersection of Signal Processing and Machine Learning If you have the original source file and