zstd Compressed chd Files [Solved]

[GamaBurst]

Question about .chd files: Now that chdman is able to compress chd using zstd algorithm (which is in every way superior to other algorithms), does anyone know if there are plans to update the MiSTer to be able to read zstd compressed chd files?

[Atohmdiy]

I have zstd compression in my ssd with btrfs and it start to become used a lot in many linux related stuff (kernel...). But from what i understand it's build to be fast, xz is a lot slower but compress a lot more ?

[GamaBurst]

Decompression of zstd compressed files is done significantly faster than for files compressed using other algorithms.
It is therefore an added value in every way. smaller file size and faster reading.

This would help reduce the size of PSX, Saturn, PC-Engine and Mega CD full sets.

[dshadoff]

No plans AFAIK.
In order to do this in the first place, the CHD decode portions in Main Mister would need to upgrade the support libraries in order to include the new code.
But that would likely be dependent on zstd libraries being part of the linux distribution, which is another can of worms if it isn’t.

And this whole discussion happens every so often when people talk of alternate compression forms (and often come supplied with incomplete and/or inaccurate information). So in general, alternative compression formats don’t tend to be a priority item, especially with the falling cost of storage.

[GamaBurst]

I just learned that this was added the the 13/03/2024 unstable MiSTer main build, so an official main build supporting this will be release eventually.

[dshadoff]

Wow, that was a big pull request too !
I never heard anything about it in the discussion groups.