I use ffmpeg to embed .ssa subtitles into mkv, but ffprobe recognizes that the subtitle is ass format.

ffmpeg -i input.avi -i input.ssa -map 0:0 -map 0:1 -map 1:0 -c copy demo.mkv

Also, I learned that ssa subtitles also support MP4, but when I use the command to convert to MP4 that ffmpeg report error:could not find tag for codec ass in stream #2, codec not currently supported in container enter image description here enter link description here

How can I solve this problem?

1 Answer 1


Mp4 container needs you specify the subtitle codec to use.
Add : -c:s mov_text
Like that :
ffmpeg -i input.avi -i input.ssa -map 0:0 -map 0:1 -map 1 -c copy -c:s mov_text demo.mp4

  • Thank you for your help!It's worked. There is identified "subtitle: mov_text" by FFprobe, but I need ssa subtitle. If I use the code like that: ffmpeg -i input.avi -i input.ssa -map 0:0 -map 0:1 -map 1 -c copy -c:s ssa demo.mkv An error reported that: Subtitle codec 94212 is not supoorted
    – mm_test
    Feb 27, 2023 at 8:56
  • @mm_test As you asked to convert to mp4 and ssa subtitles are not supported by the mp4 container, I proposed a conversion to mov_text. If you want to keep the matroska (mkv) container, ssa subtitles are supported. Normally your last command is correct. Codec 94212 matches ssa well. Check your version of ffmpeg.
    – Alain1A45
    Feb 27, 2023 at 12:53
  • Should I change the version of ffmpeg for keeping the matroska (mkv) container, ssa subtitles are supported. When I enter ‘ffmpeg -version',it's shown that: ffmpeg version N-68994-g4df01d5 Copyright (c) 2000-2015 the FFmpeg developers. Is it too old for Codec 94212?
    – mm_test
    Feb 28, 2023 at 8:28
  • 1
    @mm_test Your version is really very old. You would do well to update to benefit from bug fixes and improvements. There are releases for all platforms.
    – Alain1A45
    Feb 28, 2023 at 13:40
  • 1
    "ssa" stands for SubStation Alpha version 4.00 and "ass" stands for Advanced SubStation Alpha, the most advanced version 4.00+
    – Alain1A45
    Mar 1, 2023 at 4:18

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