I have a video which FFmpeg identifies as
720x480 [SAR 8:9 DAR 4:3]. When viewed in a player, the correctly displayed video occupies 720x540 pixels, which makes sense since 480/8*9=540.
However, when burning subtitles into the video, the subtitles are vertically stretched, by something that probably is a factor of 9/8. I assume what's happening is that the subtitles are applied to the vertically compressed 720x480 video data, and then the video player stretches the video to 720x540, which gives a correctly displayed video, but unfortunately stretched subtitles.
How do I burn subtitles into the video and maintain correct aspects for both video and subtitles? Is there any way I can "get rid of" the SAR in the conversion process, for example?
My basic command line, using FFmpeg 4.1:
ffmpeg -i in.mp4 -vf in.srt out.mp4