Although the digital TV switchover is still absorbing a lot of headlines and leaving many Americans confused, TV maker Funai has launched several silent legal attacks against competitors over the past 12 months.

Funai launched legal attacks on companies it accused of infringement on two patents related to HD technology:  patent 5,329,369 ("Asymmetric picture compression") and patent 6,115,074 ("System for forming and processing program map information suitable for terrestrial, cable or satellite broadcast").

One such company targeted by Funai is Vizio, which has filed an antitrust and unfair competition suit in the United States District Court, Central District of California.  Vizio said Funai is "acting alone and in concert with others, unlawfully restrained trade and monopolized the market for the licensing of technology used to interpret and retrieve information from a digital television broadcast signal, as well as the market for digital television sets and receivers."

Vizio believes Funai unlawfully acquired the rights to patent 6,115,074, saying Funai violated the Clayton Act, Sherman Act, and other U.S. federal and state laws related to standards all TV manufacturers must follow.

Vizio's lawsuit comes one day after the International Trade Commission (ITC) enforced a ruling saying Funai's infringement suit related to the asymmetric picture compression patent was invalid.

"Vizio, as America's HDTV Company, has been instrumental in making high quality flat panel TVs more affordable for Americans. Especially in light of the nation's digital TV transition, we won't allow a foreign competitor to divert us from our mission to bring affordable high quality HDTVs to millions of Americans," Vizio co-founder and VP sales of marketing Laynie Newsome said in a statement.