■ Embed external SRT file inside a movie

I learnt English during my studies in the UK. I can understand even Scottish accents but I have problems with many American accents, so for watching movies I turn on English subtitles. For movies that don't have subtitles I download an SRT file (basically a text file with the subtitles at various time stamps). Other Greeks download translated SRT subtitle files.

Most video players (Kodi/VLC/GOM etc) will pick the external subtitle file automatically if its base name is the same as the movie file e.g.

Women.on.the.Verge.of.a.Nervous.Breakdown.1988.MP4  
Women.on.the.Verge.of.a.Nervous.Breakdown.1988.SRT

It is quite easy to insert the SRT file inside the movie container using FFmpeg. This saves the need for the sidecar file and is perfect task for a lazy sunday with nothing better to do <g> FFmpeg can embed an .srt subtitle file directly into a video as a proper subtitle stream. This is called muxing the subtitle into the container. This is easiest for MKV movies that support SRT natively. The command line is:

ffmpeg -i movie.mkv -i subtitles.srt -c copy -c:s srt output.mkv

It combines the original movie and its srt into a single output file. The option -c copy will ensure that no re-encoding is done, so embedding the subtitles will be quick and preserve the video quality.

What about MP4 movies? I have read about converting the SRT stream into mov_text (-c:s mov_text) but the player I tried didn't recognize the subtitle stream. The best bet is to convert the MP4 into MKV, that can be done at the same time (and fast, no reencoding) as such:

ffmpeg -i movie.MP4 -i subtitles.srt -c copy -c:s srt output.MKV

Finally for older AVI movies the only option is to burn-in the subtitles inside the video stream — this is slow. Or even better, convert AVI to MKV and then add the subtitles as a soft stream as above.

To add subtitles to several MKV/MP4 movies automatically, use xplorer² user commands. Assuming the movie and the subtitles have the same name, the command template is:

c:\tools\ffmpeg -i "$N" -i "$B.srt" -c copy -c:s srt -metadata:s:s:0 language=eng "subs_$B.mkv"

The extra metadata command line switch adds a description of the subtitle language. Note that the output movie file is going to be called subs_(old name).MKV (using the $B base name token). Once you make sure the embedding works, you can delete the source movie and external SRT file.