Apple is facing a lawsuit over technology within its popular iPod digital music player and two related applications., which makes software for transmitting audio and video files over the internet, filed the suit yesterday in federal court in San Francisco.

The company alleges that Apple infringed on four patents for its iTunes jukebox application, QuickTime products and the iPod. is seeking an injunction to prevent further infringement and royalties from Apple’s use of the technology.

The suit is in response to one filed in January by Apple. That suit sought to clear Apple from any potential infringement claims and declare the patents invalid, according to has claimed a victory over another industry giant, Microsoft. In March 2005, Microsoft settled a patent quarrel by paying $60m (about £34m) for a non-exclusive licence for some of the same patents now disputed.

The suit comes as Apple faces other legal and legislative challenges that could affect its iTunes and iPod business.

In France, legislation is being debated that would require companies that use DRM (digital rights management) to reveal details about their technology that would allow other companies to make interoperable systems.

It could force Apple to disclose details of its proprietary DRM system, called Fair Play, which would break the exclusive link between its iTunes music store and iPod players. Apple has criticised the proposal, saying it could increase piracy.

On this side of the Atlantic, Apple faces a suit filed by the Beatles' record label, Apple Corps. The label is seeking an injunction against the computer company's use of its logo in advertisements and the iTunes Music Store.