ffmpeg -i ABC-123-engsub.ass ABC-123-engsub.srt
Play your video and note when a subtitle line should appear. Suppose a line is supposed to show at 02:30:59,000 but actually shows at 02:31:05,000 . That’s a (subs are 6 seconds late). HMN-625-engsub convert02-30-59 Min
To convert and manipulate subtitles, use these free, safe tools: ffmpeg -i ABC-123-engsub