Apple was hit with yet another patent infringement lawsuit this week. First, there was the suit over predictive typing, and now its the custom video backdrop feature in Leopardis iChat.

California-based Digital Background Corporation filed its case against Apple on November 14 in the Illinois Southern Federal District Court. The 1997 patent describes a process where the background in an incoming video signal is repaced by an alternate background in real time -- just like iChat can do.

While on the surface the patent and its description seem fairly clear cut, everything surrounding it is a bit murky.

The patent inventor, Michael Steffano of Austin, Texas, filed for the patent in 1997 after he founded Viewics Corporation -- a company he sold in 2001. The patent was actually assigned to The Metaphor Group in Irving, Texas, on June 9, 1998.

According to Patent Troll, Mr. Steffano recorded in 2004 that the patent had been assigned to Digital Property Management Group (DPMG) on March 18, 1997. Digital Property Group, however, wasnit actually formed until 2001. DPMGis sole member was Bruce Renourd, vice president of sales for Power Integrations -- a company that coincidentally Apple has done business with.

Canadais patent filing (available as a PDF) doesnit match the US filing, or Mr. Steffanois claims, and shows that the patent belonged to Viewics Corp.

So far, there doesnit appear to be any documentation linking this patent to Digital Background Corporation.

When a trail gets this convoluted, there is usually a surprise twist, and in this case, itis the parent company for Digital Background Corporation: Acacia Research, the same company that is suing Apple under the Autotext Technologies name over the predictive typing patent. Acacia Research doesnit actually create any products; Instead, it develops, acquires, and licenses patented technologies.

The company is asking for a permanent injunction to stop Apple from selling copies of Leopard that include the iChat backdrop feature, triple damages, and attorney fees. AppleInsider reports that the suit also asks for an order forcing Apple to recall Mac OS X 10.5 from wholesalers, destroy equipment that already has Leopard installed, and send letters to everyone that holds a copy of Leopard stating the "sale or solicited commercial transaction was wrongful."

Sticking with company policy, Apple has not commented on the case.