BDSup2Sub is a lightweight conversion tool built in Java that supports image based subtitle streams. Despite its name, the application does not only convert SUP files to SUB. Initially designed only for converting Blu-Ray / HD-DVD SUP files, the application also provides support for XML subtitles (Sony BDN), SUB, IDX (VobSub) and IFO (DVD-SUP).
The interface is split into two different panes, one for the source file and one for previewing the output. The well-organized and straightforward menus provide easy access to features, which makes it suitable for any user type.
Prior to starting the conversion process, you can set the output type (HD or FULL HD, but you can also select the NTSC or PAL standards), change the frame rate for the source and the target files, edit 'forced' flags (displayed by the video player even if subtitles are off), set subtitle delay and fix too short frames.
As changing the subtitle format may result in making the text less readable, the application comes with scaling capabilities, which means that you can scale the subtitles by a factor between 0.5 and 2.0.
It is also possible to edit the subtitle stamps and modify its position for each frame. Change the display duration (which is automatically synchronized with the frame rate, in order to avoid overlapping), manually adjust the subtitle position on the screen, transform the current subtitle to 'forced' or eliminate additional comments from the subtitle.
Frame rate conversion, invisible frame fixing, Verbatim output support are additional features available in the application.
Another advantage in the program is that it allows you to edit the default color palette and set intermediate colors for anti-aliasing and keeping the subtitle readable. IDX or IFO files come with their own imported 16-color palette, but you can also change this one according to your preferences.
Although it does not provide support for text-based formats (such as SRT or SSA), BDSup2Sub is a reliable utility for converting and editing subtitles, which advanced users can run from the command console.