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This is a follow-up question from my previous question HERE. I'm trying to convert a caption-embedded .mp4 video into a .ts file, simply changing the container format. But once I convert the video, the caption looks different. Not sure what's going on.

Here is the sample .mp4 video. At second 00:34" for example, you see the caption says GARBLED CAPTION INSERTED. But that's not there in the converted .ts file.

What's happening? Any clues?!

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The subtitles in the MP4 is a mov_text (tx3g) stream which isn't supported in MPEG-TS.

MPEG-TS support either DVD subtitles or DVB teletext. The former is a bitmap subtitle format and ffmpeg can't convert text to bitmap. FFmpeg has no encoder for the latter. Your best bet is to burn the subtitles but this means re-encoding the video.

ffmpeg -i in.mp4 -vf subtitles=in.mp4 -c:v libx264 -c:a copy out.ts
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  • what is the caption format for a regular .ts file viewable on VLC? For example: dropbox.com/s/u1unlmyketqnv1e/test.ts?dl=0 The format is different from the one created from your command.
    – angel_30
    Commented Jun 19, 2019 at 16:42
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    My command makes the captions part of the image. In your sample, the captions are embedded as an element within the video bitstream. ffmpeg can't convert subtitles from a separate stream into those.
    – Gyan
    Commented Jun 19, 2019 at 18:07
  • I see. Got it. Tnx.
    – angel_30
    Commented Jun 19, 2019 at 18:39

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