Tsunami RLB

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RLB

• Format Type : Archive
• Endian Order : Little Endian

RLB files are resource archives used in various games from Tsunami. There are several variations in the format reflecting the evolution of the format since it was used in a progression of games from the same publisher. Much of this information was gleaned from studying the source code of the ScummVM project.

Structure

RLB files are comprised of a series of resource blocks starting with a signature of 'TMI-'. Each resource block starts with the following 6-byte data structure:

bytes 0-3  'TMI-' signature
byte 4     resource type
byte 5     number of entries in this resource block

Each entry in the resource begins with the following 12-byte structure:

bytes 0-1   resource ID
bytes 2-3   compressed size
bytes 4-5   uncompressed size
byte 6      high nibbles of the compressed and uncompressed sizes
byte 7      type (bits 7-5)
bytes 8-11  payload offset

Byte 6 contains the high 4 bits of the uncompressed size in bits 7-4 and the high 4 bits of the compressed size in bits 3-0. Thus, the largest size which can be specified is 2²⁰ = 1,048,576 bytes.

The high 3 bits of byte 7 are interpreted by ScummVM as 'type' and the field is expected to be either 0 (uncompressed) or 1 (compressed).

The payload offset specifies the offset relative to the beginning of the resource block (beginning of the 'TMI-' signature).

The first resource block in the file conforms to the same general format described above, but some fields have a slightly different meaning and the header encapsulates all of the other blocks in the file as well as the block index. The compressed and uncompressed sizes match and they specify the number of resources in the file. The offset points to the index at the end of the file. Further, the block type is 32. It's possible that bit 5 of the type field means something else and bits 4-0 are the actual resource type; type 0 corresponds to 'library'.

The index consists of a series of 6-byte records. Each record is formatted as:

bytes 0-1  resource number
bytes 2-3  block type
bytes 4-5  block offset

The final entry in the index contains 0xFFFF for all 3 16-bit entries.

The block type should match the type specified in the block's TMI header.

The block offset is absolute for most games. However, in Return to Ringworld, it specifies the absolute paragraph offset (where a paragraph is defined as 16 bytes). Thus, in R2RW, all 'TMI-' signatures should be aligned to 16-byte boundaries. One curious implication of this is that there appears to be random garbage between the logical end of one resource block and the paragraph boundary of the next.

Resource Types

These are the RLB resource types known to ScummVM:

• 0: library
• 1: strip
• 2: image
• 3: palette
• 4: visage
• 5: sound
• 6: message
• 7: font
• 8: pointer
• 9: bank
• 10: sound driver
• 11: priority
• 12: control
• 13: walk regions
• 14: bitmap
• 15: save
• 16: sequence

Further, Return to Ringworld uses types 17 through 31, but ScummVM does not name them.

Compression Format

(implemented in ScummVM; to be documented)