Overview: Bitmap subtitle formats
Bitmap subtitles carry timed graphic elements that a renderer composites with the picture.
A bitmap subtitle arrives as image data rather than ordinary character strings. Its palette, placement and timing still need interpretation before composition. DVD, Blu-ray and DVB topics explain the particular representations, providing context for delivery, scaling and the separate task of turning an image into recognized text.
Bitmap subtitles
Bitmap subtitles describe timed image graphics, palettes and placement rather than storing the visible words as character text.DVD subtitles (DVDSub and VobSub)
DVD subtitle subpictures are compressed indexed graphics, while VobSub packages related subtitle data into external SUB and IDX files.Blu-ray subtitles (PGS)
PGS assembles timed Blu-ray presentation graphics from palette, object, window and composition segments.DVB subtitles (DVBSub)
DVBSub carries broadcast subtitle services using timed page, region, object and colour-table segments in a transport stream.