Sesame Street STR

This is a simple video format used in some Sesame Street related games.

File header:

 4 bytes - "STHD"
 4 bytes - version (should be 0x100)
 4 bytes - unknown
 4 bytes - unknown, usually zero
 4 bytes - audio sample rate
 2 bytes - bits per audio sample
 2 bytes - padding?

Data is organised into chunks, "GRPH" for images and palettes, "SND " for audio. Each chunk beside 32-bit usually has one nested subchunk telling what kind of data it is: for video it is either "PAL " for palette or "PIXX" for image; for audio it is "SSMP".

Image (sub)chunk has dimensions in its header and stores raw data in permuted form: by VGA bank (i.e. every fourth column) where data is also 4-way interleaved.