1. sub_source for current sub source (sub file, vobsub, or from demuxer).
2. sub_file for all subtitles from files.
3. sub_vobsub for all subtitles from vobsub.
4. sub_demux for all subtitles from demuxer.
Now mplayer can supply a stable and clear interface to external programs
using mplayer in slave mode to select a subtitle by its source and
its unique id for that source printed by mplayer using -identify parameter.
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@25157 b3059339-0415-0410-9bf9-f77b7e298cf2