Optimizing CHD block sizes for CD-ROM systems...

[Alopex]

I know to use a hunk size of 2048 for PS2/DVD and PSP games when using CHDMan, but now I'm looking for the "most effective compression, but without impacting performance" for each of the CD-ROM based platforms. I've seen collections using a hunk size of 2448 rather than the default 19584, and I'm wondering what to go with to rebuild my collection... have any recommended block sizes for any particular consoles been established at all? Is 2448 really just a performant sweet zone for standard CDs? Do any systems have a weird disc format that benefits from a different hunk size? Is it even worth changing the hunk size for older, less taxing systems, like Sega CD/PC-Engine unless I'm trying to run them on a potato?

Any advice would be appreciated.

 

[secreto7]

I'd say better not bother that much with CHD at least for CD based games.

Apparently it have problems for preserving some data for CDs, and the devs I think said it wasn't really meant for lossless archival.

See all the info here:
Post in thread 'Ymir' https://retrogametalk.com/threads/ymir.9038/post-210186

 

[Deleted member 132407]

It can be a pain since some disc images can't be converted, some are better off left alone.

 

[Alopex]

I'd say better not bother that much with CHD at least for CD based games.

Apparently it have problems for preserving some data for CDs, and the devs I think said it wasn't really meant for lossless archival.

See all the info here:
Post in thread 'Ymir' https://retrogametalk.com/threads/ymir.9038/post-210186

It depends, the vast majority of games have no issues in the format and the few that do aren't gamebreaking, and if I hit a game with index issues, I can just decompress it. Other than the Dreamcast CHDs deleting padding bytes, I haven't encountered any systems whose games do not restore data byte-for-byte to raw format, and any cue sheet problems can be compensated for by keeping backups of the originals.

The format may not be perfect yet, but the convenience and space saving is well worth it when most of the caveats can be worked around.

 

[secreto7]

It depends, the vast majority of games have no issues in the format and the few that do aren't gamebreaking, and if I hit a game with index issues, I can just decompress it. Other than the Dreamcast CHDs deleting padding bytes, I haven't encountered any systems whose games do not restore data byte-for-byte to raw format, and any cue sheet problems can be compensated for by keeping backups of the originals.

The format may not be perfect yet, but the convenience and space saving is well worth it when most of the caveats can be worked around.

You could be right, better if it's like you say.
Just wanted to inform.

Post automatically merged: Jul 10, 2025

Also appreciate your input, since I tried to use them but desisted because of that and it was a bit of a hassle to me.