BDSup2Sub is a tool initially created to convert captions demuxed from a Blu-Ray transport stream (M2TS) into the DVD VobSub format (SUB/IDX) used by many DVD authoring tools - hence the name. Many more features were added over time as was support for other formats. So in the meantime the name seems a little inappropriate. In a nutshell, it's a subtitle conversion tool for image based stream formats with scaling capabilities and some other nice features.
BDSup2Sub only supports image based subtitle streams. It doesn't (and probably won't ever) support text based formats as SRT or SSA. Note that to convert image based subtitles to text based subtitles would need an OCR (Optical Character Recognition) approach which is beyond the idea of converting between image based formats. There are other tools like SubRip and SupRip to convert image based subtitles to SRT.
While importing HD-DVD SUPs is supported, BDSup2Sub can't export this format currently - and with the commercial death of HD-DVD I think adding this feature would be a waste of time.
Originally created by Volker Oth (2009); currently maintained and developed by Miklos Juhasz.
BDSup2Sub © 2009 Volker Oth, 2011-2013 Miklos Juhasz