[FFmpeg-user] Can I add a codec for compatibility and automatically keep the original?

[bbb]

Hi,

when I have a file using advanced subtitles, I often want to keep those 
for most devices but also add a basic subtitle format that is supported 
by my TV.

So far, I've been converting the subtitles and after that, mapping the 
different subtitle format from the original and the output file into a 
final file in a second operation. Surely it would also be possible to 
map the original subtitles twice and then copy all codecs and convert 
only that of the second subtitle stream.

I am planning to work on an automation (that works on a directory 
without knowing the number of streams in each file) and wondering, if 
ffmpeg maybe already has the kind of feature that I am looking for.

Kind regards