[mythtv-users] Transcoding DVB from MPEG2 to MP4 keeping the subtitles

[Doug Vaughan]

Ken,
     I am working on a script that changes a recorded video's container 
type to MKV plus retains the subtitle track(s). I have found at least 
for UK DVB recordings that ffmpeg/avconv and even mkvmerge will support 
only a limited amount of subtitle formats (mostly SRT), while dropping 
any unsupported subtitle tracks.

     A working solution is to extract the subtitle track from the 
recording, convert it to srt format and then remux it back into the 
recording while it is being converted to a new container type. I use 
mkvmerge and obviously a mkv container to do the remux of the srt 
subtitle file.

See these subtitle extraction tools that convert the subtitles to a srt 
file:

mythccextractor - see http://www.mythtv.org/wiki/Mythccextractor
Be aware of this ticket which may or may not effect you: 
http://code.mythtv.org/trac/ticket/11081

CCExtractor - see http://ccextractor.sourceforge.net/
With UK DVB text subtitle tracks it had a bug but the developer has 
fixed that issue in an unreleased version 0.64. He has told me that he 
will release 0.64 in a week or so.

telexcc - see: https://github.com/forers/telxcc
This one is no longer under active development but its code has been 
included in CCExtractor. Oddly enough it does not have issues with UK 
DVB text subtitle tracks.

mkvmerge command line to remux your srt subtitle file into a mkv container:
 > mkvmerge -o "new_video.mkv" "/path to/recorded.mpg" "/path 
to/subtitle_file.srt"

My advise is to use the latest versions of the MKVToolNix utilities.
See:
     https://www.bunkus.org/videotools/mkvtoolnix/downloads.html
     https://www.bunkus.org/videotools/mkvtoolnix/source.html

I hope this helps.

Doug