Lawsuit accuses Apple, Dell, HTC of infringing MP3-related patent

Hybrid Audio is the owner of U.S. Patent No. RE40,281, entitled "Signal Processing Utilizing a Tree-Structured Array." Reissued in 2008, it describes "signal processing" that is accomplished by "splitting a signal into subbands using a plurality of filter banks connected to form a tree-structured array."

The application references "audio signals," but makes no mention of MP3 files or the MPEG-1 Layer III standard. But the lawsuit targets Apple, HTC and Dell for creating devices that allow playback of MP3 files.

Specifically named in the complaint are a number of Apple products, including the iPod nano, iPhone 4, iPad, MacBook Pro, and iTunes software. The suit targets products "that contain or use hardware and/or software for processing audio information in accordance with the MPEG-1 Layer III (MP3) standard."

Other products named include the HTC Evo 4G smartphone, and a number of computers from Dell including Inspiron, Studio, Alienware, Adamo and XPS.

Little about Hybrid Audio LLC can be found online, but the patent was first filed in 1997 by a Massachusetts company called "Aware, Inc." Hybrid Audio seeks damages from the companies it is suing, and asserts that they are infringing, contributing to infringement, and inducing infringement of the '281 patent.