GCZ, RVZ and WIA size comparison

Published: Dec 29, 2020, last updated: Jul 30, 2025

Reading time: 2 min

Tags: Emulation, Formats, Games, Media, Software

For as long as I can remember, the Dolphin emulator has supported GCZ compression, and since version 5.0-12188, it has added two new formats, WIA and RVZ (as outlined in this blog post). The original post has a quick overview of size comparisons, but it doesn’t detail how well each compression method works.

I tried this with Kururin Squash!, a Japanese exclusive Gamecube game and sequel to the GBA exclusive Kuru Kuru Kururin. No junk data was removed during any of these tests.

The compressed sizes were as follows, with percentage values to match:

Format	Size (bytes)	Relative size (percent)
ISO (Original)	1,459,978,240	610.57
ISO (Uncompressed)	239,116,400	100.00
GCZ (Standard)	107,272,770	44.87
WIA (No Compression)	239,149,168	100.01
WIA (Purge)	229,449,768	95.96
WIA (2MiB, bzip2, level 1)	106,515,768	44.55
WIA (2MiB, bzip2, level 5)	105,127,440	43.97
WIA (2MiB, bzip2, level 9)	104,732,188	43.79
WIA (2MiB, LZMA, level 1)	91,674,188	38.34
WIA (2MiB, LZMA, level 5)	86,715,744	36.26
WIA (2MiB, LZMA, level 9)	86,618,716	36.22
WIA (2MiB, LZMA2, level 1)	91,688,008	38.34
WIA (2MiB, LZMA2, level 5)	86,728,708	36.27
WIA (2MiB, LZMA2, level 9)	86,728,708	36.27
RVZ (128KiB, bzip2, level 1)	106,771,616	44.66
RVZ (128KiB, bzip2, level 5)	106,339,216	44.47
RVZ (128KiB, bzip2, level 9)	106,339,216	44.47
RVZ (512KiB, bzip2, level 1)	106,568,640	44.57
RVZ (512KiB, bzip2, level 5)	105,239,600	44.01
RVZ (512KiB, bzip2, level 9)	105,093,188	43.95
RVZ (2MiB, bzip2, level 1)	106,515,768	44.55
RVZ (2MiB, bzip2, level 5)	105,127,440	43.96
RVZ (2MiB, bzip2, level 9)	104,732,188	43.80
RVZ (128KiB, LZMA, level 1)	96,654,712	40.42
RVZ (128KiB, LZMA, level 5)	92,597,268	38.72
RVZ (128KiB, LZMA, level 9)	92,521,648	38.69
RVZ (512KiB, LZMA, level 1)	93,891,916	39.27
RVZ (512KiB, LZMA, level 5)	89,668,640	37.50
RVZ (512KiB, LZMA, level 9)	89,586,320	37.47
RVZ (2MiB, LZMA, level 1)	91,674,188	38.34
RVZ (2MiB, LZMA, level 5)	86,715,744	36.27
RVZ (2MiB, LZMA, level 9)	86,618,716	36.22
RVZ (128KiB, LZMA2, level 1)	96,666,280	40.43
RVZ (128KiB, LZMA2, level 5)	92,608,300	38.73
RVZ (128KiB, LZMA2, level 9)	92,532,604	38.70
RVZ (512KiB, LZMA2, level 1)	93,905,124	39.27
RVZ (512KiB, LZMA2, level 5)	89,681,068	37.51
RVZ (512KiB, LZMA2, level 9)	89,598,776	37.47
RVZ (2MiB, LZMA2, level 1)	91,688,008	38.34
RVZ (2MiB, LZMA2, level 5)	86,728,708	36.27
RVZ (2MiB, LZMA2, level 9)	86,631,708	36.23
RVZ (128KiB, Zstandard, level 1)	111,340,684	46.57
RVZ (128KiB, Zstandard, level 5)	105,730,496	44.22
RVZ (128KiB, Zstandard, level 10)	104,140,564	43.56
RVZ (128KiB, Zstandard, level 22)	100,217,436	41.91
RVZ (512KiB, Zstandard, level 1)	109,719,948	45.89
RVZ (512KiB, Zstandard, level 5)	103,921,924	43.46
RVZ (512KiB, Zstandard, level 10)	102,535,204	42.88
RVZ (512KiB, Zstandard, level 22)	97,270,064	40.68
RVZ (2MiB, Zstandard, level 1)	108,380,880	45.33
RVZ (2MiB, Zstandard, level 5)	100,285,556	41.94
RVZ (2MiB, Zstandard, level 10)	98,800,396	41.32
RVZ (2MiB, Zstandard, level 22)	93,857,212	39.25

As you can see, from this extremely limited test, the best performing archive format is LZMA using a 2MiB block size at compression level 9. It doesn’t matter which container, out of RVZ and WIA you use.