BSS (Resident Evil 1997)
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The .BSS file format is used on Resident Evil game series on Playstation to store the 2D background images. A file holds all different views (camera angles) for the same room.
Structure
The file is an archive that contains several compressed images, aligned on 32KB boundaries (for Resident Evil) or 64KB boundaries (Resident Evil 2 and 3).
Decompression
Each image is compressed for use with Playstation MDEC decoder (the chip responsible for video decoding). An extra decompression step in software, to decode variable-length data (VLC), is performed before feeding the data through MDEC processing.
The libbs library from psxdev-libs package provides the two necessary routines/steps to fully depack the images. The MDEC decoding part in this library comes from the PCSX emulator.
The resolution of the image must be known for correct depacking, and these images use standard 320x240 resolution.