Use ffmpeg to add text subtitles

Question

I am trying to add text subtitles to an .mp4 container using ffmpeg:

ffmpeg -i input.mp4 -i input.srt -map 0.0 -map 0.1 -map 1.0 output.mp4

When I am trying to run this line, it gives me an error :

Nmber of stream maps must match number of output streams.

If I try to change the mp4 to mkv (although mp4 supports text subtitles), like this:

ffmpeg -i input.mp4 -i input.srt -map 0.0 -map 0.1 -map 1.0 output.mkv

It correctly maps the streams, but gives an error :

Encoder (codec id 94210) not found for output stream #0.2

When I launch

ffmpeg -codecs

I can see that srt codec is supported as decoder and encoder, however I am not sure what is used for mp4 and mkv subs encoding, and whether I need to switch it on or compile separately.

Answer 1

ffmpeg -i infile.mp4 -i infile.srt -c copy -c:s mov_text outfile.mp4

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-vf subtitles=infile.srt will not work with -c copy

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The order of -c copy -c:s mov_text is important. You are telling FFmpeg:

1. Video: copy, Audio: copy, Subtitle: copy
2. Subtitle: mov_text

If you reverse them, you are telling FFmpeg:

1. Subtitle: mov_text
2. Video: copy, Audio: copy, Subtitle: copy

Alternatively you could just use -c:v copy -c:a copy -c:s mov_text in any order.