#11602: Muxing MKV and adding external SRT as anything except the only subtitle stream in an MKV prevents subtitle display in VLC -------------------------------------+------------------------------------- Reporter: Kurt | Type: defect Fitzner | Status: new | Priority: normal Component: | Version: git- undetermined | master Keywords: mkv srt | Blocked By: muxer remux | Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | -------------------------------------+------------------------------------- Summary of the bug: When re-muxing an MKV video that already has subtitle streams in it to add an additional external subrip .srt file, if the external .srt is included as anything except the only subtitle stream in the output then the added external subtitle will not display in VLC or on a Roku media player. You can select any number of existing subtitle stream from the input MKV video and they will properly copy to the output and display when the video is played. The following produces videos where the added external subtitle DOES NOT display, but where the subtitle stream included from the input .mkv DOES display: {{{ % ffmpeg -report -i invid.mkv -i 1b.srt -map 0:v? -c:v copy -map 0:a? -c:a copy -map 0:s:0 -c:s:0 copy -map 1:s:0 -c:s:1 copy outvid1.mkv % ffmpeg -report -i invid.mkv -i 1b.srt -map 0:v? -c:v copy -map 0:a? -c:a copy -map 1:s:0 -c:s:0 copy -map 0:s:0 -c:s:1 copy outvid2.mkv }}} The following produces a video where the added external subtitle (the same one as the above) DOES display properly: {{{ % ffmpeg -i invid.mkv -i 1b.srt -map 0:v? -c:v copy -map 0:a? -c:a copy -map 1:s:0 -c:s:0 copy outvid3.mkv }}} This was attempted on ffmpeg Windows 64 builds: ffmpeg version 2025-05-07-git-1b643e3f65-full_build-www.gyan.dev ffmpeg version 2025-05-19-git-c55d65ac0a-full_build-www.gyan.dev -- Ticket URL: <https://trac.ffmpeg.org/ticket/11602> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker