.CSO is a compression method for the
ISO imageformat. It is used to compress dumped PlayStation Portable UMDgames, and is an alternative to the .DAXcompression method.
At one time, .DAX was the compression standard among PSP games. However, with the wildly popular homebrew application "
DevHook" using the .CSO compression standard, .CSO has become more popular. Due to compression, one may also experience slightly longer loading times when playing .CSO games instead of ISO imageformat.
CSO provides nine levels of compression. While the highest levels of compression can introduce slowdown and lengthy load-times in software which relies heavily on disc streaming, even the lower levels are capable of substantial compression. [cite web | url=http://www.fileinfo.net/extension/cso | title=CSO compression | accessdate=2008-02-28] This is partially due to the data layout of a UMD, though more frequently due to the use of
Dummy Files as both an anti-piracy tool and a means to more optimally lay the data out physically on the disc.
In addition to being used for compressing
PlayStation Portable UMDgames, the PSP port of PicoDrive supports compressed Sega Mega-CDdisc images in the CSO format [cite web | url=http://pspupdates.qj.net/PicoDrive-for-PSP-v1-35b-bugfixes-and-major-feature-added/pg/49/aid/108461 | title=PicoDrive for PSP v1.35b - bugfixes and major feature added | accessdate=2007-12-11] .
Related file formats
* BWT, BWI, BWS, BWA
* CSO (.cso)
* DAA (.daa)
* MDF/MDS (.mdf)
* NRG (.nrg)
* DMG (Apple disk image) (.dmg)
* UIF (Universal Image Format) (.uif)
* IMA (.ima)
* IMG (.img)
* DK (.dk)
* WIM (.wim)
* [http://filext.com/detaillist.php?extdetail=.cso&Search=Search File Extension Details for .CSO]
Wikimedia Foundation. 2010.