FFMPEG subtitle codec image/text list breakdown

list.txt

TEXT    ..S... arib_caption         ARIB STD-B24 caption
TEXT    DES... ass                  ASS (Advanced SSA) subtitle (decoders: ssa ass ) (encoders: ssa ass )
IMAGE   DES... dvb_subtitle         DVB subtitles (decoders: dvbsub ) (encoders: dvbsub ) 
IMAGE   ..S... dvb_teletext         DVB teletext 
IMAGE   DES... dvd_subtitle         DVD subtitles (decoders: dvdsub ) (encoders: dvdsub )
TEXT    D.S... eia_608              EIA-608 closed captions (decoders: cc_dec )
IMAGE   D.S... hdmv_pgs_subtitle    HDMV Presentation Graphic Stream subtitles (decoders: pgssub )
TEXT    ..S... hdmv_text_subtitle   HDMV Text subtitle
TEXT    D.S... jacosub              JACOsub subtitle
TEXT    D.S... microdvd             MicroDVD subtitle
TEXT    DES... mov_text             MOV text
TEXT    D.S... mpl2                 MPL2 subtitle
TEXT    D.S... pjs                  PJS (Phoenix Japanimation Society) subtitle
TEXT    D.S... realtext             RealText subtitle
TEXT    D.S... sami                 SAMI subtitle
TEXT    ..S... srt                  SubRip subtitle with embedded timing
TEXT    ..S... ssa                  SSA (SubStation Alpha) subtitle
TEXT    D.S... stl                  Spruce subtitle format
TEXT    DES... subrip               SubRip subtitle (decoders: srt subrip ) (encoders: srt subrip )
TEXT    D.S... subviewer            SubViewer subtitle
TEXT    D.S... subviewer1           SubViewer v1 subtitle
TEXT    DES... text                 raw UTF-8 text
TEXT    ..S... ttml                 Timed Text Markup Language
TEXT    D.S... vplayer              VPlayer subtitle
TEXT    DES... webvtt               WebVTT subtitle
IMAGE   DES... xsub                 XSUB

Very useful!

subs_text_codecs = ['arib_caption', 'ass', 'eia_608', 'hdmv_text_subtitle', 'jacosub', 'microdvd', 'mov_text', 'mpl2', 'pjs', 'realtext', 'sami', 'srt', 'ssa', 'stl', 'subrip', 'subviewer', 'subviewer1', 'text', 'ttml', 'vplayer', 'webvtt']
subs_video_codecs = ['dvb_subtitle', 'dvb_teletext', 'dvd_subtitle', 'hdmv_pgs_subtitle', 'xsub']