[FFmpeg-user] Convert MKV to MKV - convert video and audio streams - retain subtitle and font attachements

[Ben Longman]

I've been looking to find a way to do this to entire directories of files
in order to create streams that are more amenable to hardware decode.  So
far this has gone well for converting old AVIs to MP4 files, but some of
the files I have are Hi10P encoded with multiple subtitle and font
attachments (I can't say that I prefer this) and I'd like to avoid the
complication of trying to automate burning in of subtitles.

For AVI and MKV files without soft subtitles, I do something like this:

for i in *.mkv ; do
$FFMPEG -n -i $i -strict -2 -c:v libx264 -profile high -crf 23 -ac 2 -c:a
aac $i.mp4
done

I've tried this:

for i in *.mkv ; do
$FFMPEG -n -i $i -strict -2 -c:v libx264 -profile high -crf 23 -ac 2 -c:a
aac -c:s copy -c:t copy convert/$i
done

And it copies the subtitle stream, but the font attachments don't copy.

Does anyone know how to do this without manual intervention or more complex
scripting?

Thanks,

-Ben