Short header mode
is (baseline) H.263 compatible, with minimum set of resolutions, defined by source_format
syntax, not including resolutions such as 320x240, 720x480.
Non short header
mode is not H.263 compatible, and can code other resolutions beyond the minimum
set of resolutions for baseline H.263.
Custom resolution
support in H.263 some feature in H.263+ (H.263 v2).
Microsoft MPEG-4 Part 2 Video Decoder supports both
short header mode (baseline H.263) and non short header mode, but not H.263+
and H.263++, up to Windows Blue.
