chdman copy -i old_v4.chd -o new_v5.chd -c zstd (zstd = Zstandard compression; others: lzma, flac, huffman) Assume you have a folder of BIN/CUE PS1 games.
Open a terminal in that folder.
chdman createhd -i input.raw -o output.chd -s source_size_in_bytes (Modern MAME often auto-detects size, but you may need -s for raw dumps.) Useful for modding or verifying: chdman
Storing raw, uncompressed disc images (like BIN/CUE, ISO, or GDI) for PlayStation, Sega Saturn, or arcade hard drives consumes terabytes of space. Enter (Compressed Hunks of Data MANager). What is CHDMAN? CHDMAN is a command-line tool bundled with MAME. It converts raw disk images into the CHD (Compressed Hunks of Data) format. This format applies lossless compression to disc sectors, often reducing file sizes by 40–60% without losing any data.
chdman createcd -i "Final Fantasy VII Disc 1.cue" -o "Final Fantasy VII Disc 1.chd" Use createcd with a GDI file. chdman copy -i old_v4
| Emulator | CHD Support | |----------|--------------| | MAME / MESS | ✅ Native | | RetroArch (MAME core) | ✅ | | DuckStation (PS1) | ✅ | | PCSX2 (PS2) | ✅ (since recent builds) | | Redream (Dreamcast) | ✅ | | AetherSX2 (Android PS2) | ✅ | | Flycast (Dreamcast/Naomi) | ✅ |
chdman extracthd -i harddrive.chd -o extracted.raw Checks the internal hashes without extracting: Enter (Compressed Hunks of Data MANager)
chdman extractcd -i game.chd -o extracted.cue For hard drives: