yaz0encdec

yaz0encdec is a small C99 command-line tool for compressing and decompressing supported Nintendo 64 Zelda ROMs.

It understands the ROM's DMA table, detects the ROM version from the embedded build date, and recompresses each file with the codec used by that ROM family:

• Yaz0 for the standard N64, GameCube and Master Quest ROMs.
• raw deflate for iQue ROMs, including the iQue footer format.

The project is dependency-free. Yaz0, raw deflate encode/decode, DMA handling and N64 CRC calculation are all implemented in this source tree.

The tool was created as a study of how Zelda 64 ROMs are structured, how the DMA file table maps virtual addresses to physical segments, and how those segments are compressed.

Supported ROMs

• NTSC 1.0, 1.1, 1.2
• PAL 1.0, 1.1
• NTSC GameCube
• PAL GameCube
• NTSC Master Quest
• PAL Master Quest
• iQue
• All Swedish ROMs
• Majora's Mask NTSC-U
• Majora's Mask NTSC-U GameCube
• Majora's Mask PAL 1.0
• Majora's Mask PAL 1.1
• Majora's Mask PAL GameCube

Unknown ROMs are rejected instead of guessed. The version table lives in src/romdb.c.

Usage

Compress a decompressed ROM:

./yaz0encdec --compress --in input.z64 --out output.z64

Decompress a compressed ROM:

./yaz0encdec --decompress --in input.z64 --out output.z64

Short forms are also available:

./yaz0encdec -c --in input.z64 --out output.z64
./yaz0encdec -d --in input.z64 --out output.z64

Batch-compress every recognized .z64 file in a directory:

./yaz0encdec --batchc --in source_dir --out target_dir

Batch-decompress every recognized .z64 file in a directory:

./yaz0encdec --batchd --in source_dir --out target_dir

Batch mode skips unrecognized ROMs and writes recognized ROMs to the target directory using the same filenames.

Building

Build the native Linux binary:

make native

This produces yaz0encdec.

Build the Windows executable from WSL/Linux:

make

This requires x86_64-w64-mingw32-gcc from mingw-w64 and produces yaz0encdec.exe.

Remove generated build outputs:

make clean

Source Layout

src/
  main.c              command-line parsing and batch mode
  romdb.c/.h          ROM version database, codec selection and skip lists
  dma.c/.h            DMA table parsing, validation and writing
  compress.c/.h       full-ROM compression pipeline
  decompress.c/.h     full-ROM decompression pipeline
  yaz0.c/.h           Yaz0 encoder and decoder
  zlib.c/.h           wrapper for OoT zlib/raw-deflate file formats
  deflate.c/.h        dependency-free raw deflate decoder and public API
  deflate_encode.c    dependency-free raw deflate encoder
  n64crc.c/.h         N64 ROM checksum calculation
  util.c/.h           shared byte I/O, alignment and allocation helpers
Makefile
README.md

Notes

For iQue ROMs, the deflate stream is stored without a normal zlib header. The tool writes the raw deflate payload followed by the iQue footer: CRC32 and uncompressed size, both little-endian.