CHD files

CHD

CHD is a lossless compression format originally developed for MAME, for the hard-drive contents of certain arcade machines. It has since been used in several other emulators as a means of storing CD-ROM game data. For CD-based games, it compresses the contents of a disc image (.cue + .bin files) to a single .chd file.

Creating CHDs from CD-ROMs

CHD files can be created using the chdman program, developed by the MAME project.
It is a command line application and creating a .chd file from an existing .cue is performed by running:

chdman createcd -i <game.cue> -o <game.chd>

To compress every file in a directory, use:

cd /path/to/folder
for i in *.cue; do chdman createcd -i "$i" -o "${i%.*}.chd"; done

To compress every file in subdirectories within a folder, use:

cd /path/to/folder
for i in */*.cue; do chdman createcd -i "$i" -o "${i%.*}.chd"; done

Windows

The following archive contains a MAME 0.205 version of CHDMAN and Windows batch files that can be used to quickly convert your PSX games to CHD (V5): Download

Run the appropriate batch file in the same folder as the ROM(s) you wish to compress, and it will search subfolders for .cue files to compress. If a .chd is not generated after running the appropriate batch, then something is wrong with the ROM(s) .cue.

MacOS

In MacOS, chdman can be installed through Homebrew, with the following command:

brew install rom-tools

Linux

On Debian based systems, including RetroPie, chdman can be found in the mame-tools package and can be installed with:

sudo apt install -y --no-install-recommends mame-tools