Ok, here it is.
SupTitle: an AviSynth PGS (.SUP) Subtitle Plugin
# Supported colorspaces - YV12, YUY2, RGB24, RGB32
# SIMD optimizations
# Alpha channel transparency blending
# Handles both HD-DVD and Blu-ray .SUP subtitle files extracted by eac3to
# Perfect for hardsubbing forced subtitles with forced flag detection (e.g. subs for foreign dialogues)
# Supports seek and jump
Note: It takes a while to start especially with large SUP files. SupTitle reads, verifies and caches all the SUP metadata on startup.