All multi-byte integers are little endian
header{ uint8_t[4] magic; // "YBE\0" uint32_t sector_count; uint8_t crunch; //Defines how the sector modelling is stored };
raw_sector_encoding{ uint8_t type; //type byte encoding the type of the sector and flags for which elements are unmodelled uint8_t *unmodelled; //unmodelled elements in the order they appear in the sector }
file_format{ header; uint8_t *modelling; //varies based on crunch type uint8_t *data; //All data sections concatenated in order }
Crunch byte could double as a version byte for any breaking change beyond it, not just adding new encoding types. Decoder always exits on unrecognised crunch byte.
- Raw: crunch=0 A raw_sector_encoding for every sector, the fallback if a more compact form isn't found
- Perfect: crunch=1..4 The entire image consists of only one sector type and every non-data element is perfectly modelled. 1=M1 2=M2F1 3=M2F2 4=RAW
* Sectors are encoded as one of 4 types: M1, M2F1, M2F2, RAW
* A sector is determined to be mode 1 if sync and mode are correct
* A sector is determined to be M2F1 or M2F2 if:
* Sync and mode are correct
* The subheader is correctly repeated
* F1/F2 is determined by the form bit in the subheader
* A sector is raw otherwise, mostly audio but also intentionally corrupt sectors
or rare sector types like mode0
Type bits
xascpqtt
When a flag is set it means the section could not be modelled
x: unused flag a: address flag s: sub/intermediate flag c: EDC flag p: ECC P flag q: ECC Q flag tt: Sector type. 0..3 M1/M2F1/M2F2/RAW