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Compressed ISO
Filename extension .cso
Internet media type application/x-compressed-iso
Developed by Booster
Type of format Disk image
Container for ISO images

.CSO is a compression method for the ISO image format. It is used to compress dumped PlayStation Portable UMD games, and is an alternative to the .DAX compression method. It is also sometimes called "CISO".

It was the first compression method for ISO. It was created so that more memory space can be saved. Booster created the first code; it was later optimized for better compression. Other formats tried to replace it by fixing up certain issues such as lag in games, such as .DAX and .JSO. However at the time, the popular application homebrew "DevHook" used CSO. .DAX needed another loader, and .JSO was basically unused.

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.[1] 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 UMD games, the PSP port of PicoDrive supports compressed Sega Mega-CD disc images in the CSO format.[2]


  1. ^ "CSO compression". Archived from the original on 23 February 2008. Retrieved 2008-02-28. 
  2. ^ "PicoDrive for PSP v1.35b - bugfixes and major feature added". Archived from the original on 12 December 2007. Retrieved 2007-12-11. 

External links[edit]

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/.CSO — Please support Wikipedia.
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670978 news items

CSO Online

CSO Online
Fri, 27 Mar 2015 13:15:00 -0700

Slack, a popular start-up focused on collaboration in the workplace, said on Friday that a database storing user profile information was compromised in February. The incident lasted four days, but the company said that only a small number of users were ...

CSO Online

CSO Online
Fri, 27 Mar 2015 10:15:00 -0700

Mobile malware is a growing problem, but researchers from University of Alabama at Birmingham have figured out a new way of detecting when shady mobile apps get up to no good, such as trying to call premium-rate numbers unbeknowst to a phone's ...

CSO Online

CSO Online
Fri, 27 Mar 2015 07:34:29 -0700

Many technology companies, like Adobe, face the daunting challenge of implementing a comprehensive security program across a mixture of both legacy infrastructures, acquired product platforms, and newly deployed cloud-based SaaS offerings. Successful ...
Fri, 27 Mar 2015 12:41:15 -0700

In his capacity as a CSO Young was responsible for code enforcement and traffic control. “James' seriousness about his career, coupled with his devotion to the community of Prineville, has shown me that he's ready to take the next step. I'm very proud ...

CSO Online

CSO Online
Thu, 26 Mar 2015 17:22:30 -0700

Open-source software projects are often well intended, but security can take a back seat to making the code work. OpenDaylight, the multivendor software-defined networking (SDN) project, learned that the hard way last August after a critical ...

CSO Online

CSO Online
Fri, 27 Mar 2015 04:03:45 -0700

The total number of distributed denial of service attacks declined steadily last year, from more than 450,000 attacks in the first quarter to fewer than 150,000 in the fourth quarter -- but the size and complexity of the average attack both increased ...

Chicago Tribune

Chicago Tribune
Fri, 27 Mar 2015 08:33:45 -0700

So it was incumbent on the CSO management to return the favor by inviting de Waart back through the front door. He got his payback on Thursday night at Symphony Center, where the program this time was entirely of his own making, not something he ...

Chicago Tribune

Chicago Tribune
Fri, 20 Mar 2015 08:51:39 -0700

The weekend CSO subscription concerts, with conductor Charles Dutoit completing a two-week, all-French mini-festival, amount to nothing less than a Yo-Yo Ma marathon of French works for cello and orchestra. Few, if any, of our top cellists would have ...

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