Emulator

[21:56:22] GC stuff doesn't roundtrip because our uncompress routine is kinda stupid, but the compression is lossless

Gamecube discs have garbage data in them just like Wii discs. Doesn't the compression routine wipe this data in order to achieve this compression? In which case, this would be expected behavior.

No. Gamecube compression is lossless, we don't scrub Gamecube discs at all.
Scrubbing Gamecube discs is dangerous and we refuse to do it.

I see, I didn't know that. Why is it more dangerous than Wii discs, can you elaborate on the dangerous part? I scrubbed all my GC discs with a separate tool when I ripped them so I could compress them with 7zip, so they always compressed well in Dolphin without me realizing.

I did some investigating of my own for this issue, I reripped four of my games, compressed and decompressed them and examined the differences. On all four, the last 360448 bytes (exactly 352k) was zeroed out where there used to be data. This starts at address 0x57000000 in the image.

If I have some time later, I may try to figure out what build this started in.

I did have time, and managed to track it down to build 4.0-4402.

https://dolphin-emu.org/download/dev/6df67bf38f52151ee5efb64edb4bc60ecce601ef/

Sweet! Thanks for the hard work. :D

What is the file size of the iso/gcm in bytes before compression and after decompression?

I don't have a copy of Nightfire, would it be OK if I give you the sizes for another iso?

Yes, any iso where you have seen this problem.

The Legend of Zelda - The Wind Waker:
Before compression - 1,459,978,240 bytes
After decompression - 1,459,978,240 bytes

Sorry if I wasn't clear on that. The decompressed images are the correct size (1,459,978,240 bytes), but the problem is they are zero-filled (0x00) for the last 352k instead of the data that should be there.

Could you try compressing with the latest dolphin and decompressing the gcz with an old version? And vice versa and let us know the results?

Will do!

Original image:
SHA-1 = eed83fea6eccb3ba4092b998fcdf4cc57f5ba6b4

Compressed by -4199, decompressed by -5168:
SHA-1 = abe18704d79021d41aff17c4d2285d515d6fbb71

Compressed by -5168, decompressed by -4199:
SHA-1 = eed83fea6eccb3ba4092b998fcdf4cc57f5ba6b4

You can try this, which should have it resolved:

http://dl.dolphin-emu.org/prs/pr-2042-dolphin-latest-x64.7z

-[Unknown]

I quick check shows PR 2042 does indeed fix the issue, I get the same MD5 after decompressing as before.