English to Croatian Tech/Engineering Media / Multimedia e-learning Software

https://en.wikibooks.org/wiki/Inside_DVD-Video/Subpicture_St...

Subpictures are used to display subtitles as well as menu buttons, overlaid on the video. These are stored in an MPEG stream (private stream 1) as a sequence of Sub-Picture Units (SPUs). SPUs may be broken across multiple MPEG stream packets.

Each SPU contains an image bitmap with 2 bits per pixel, split into odd and even fields, stored using a run-length-encoded (RLE) compression format. This is accompanied by a sequence of commands that control the actual display of the bitmap, including the choice of which four colours from the PGC colour table to use. There is also a time delay that can be specified before executing the commands