NullSoft is the maker of the popular MP3 player, called WinAmp -- or is it? That's the question brought forward by the suit. "We did not file this case lightly," said Henry D. Gradstein, a partner with law firm Gradstein, Luskin & Van Dalsem, representing PlayMedia. "We researched both products extensively and believe that we can prove our claims." On Friday, PlayMedia filed a complaint in Los Angeles District Court accusing NullSoft of copying its AMP digital music player to create the basic engine of NullSoft's popular WinAmp. The Los Angeles company is asking for $20m (£12m) in damages and a court order forbidding NullSoft from distributing its software. The case is confused by the fact that initially NullSoft was copying PlayMedia's software, and had a license to do it. The code used by NullSoft comprised parts of the "engine" needed to decode highly-compressed CD-quality music files known as MPEG-1, Layer 3 files or MP3. Originally, this code had been provided to NullSoft from PlayMedia. "While it is true that WinAmp initially licensed code for the decoding of MPEG audio files from Tomislav Uzelac [of PlayMedia], this code was replaced with proprietary code developed by NullSoft as of June 1998," stated NullSoft in its response to the suit. Not so, said attorney Gradstein. "We were originally told that NullSoft stopped using the code in April 1998," he said. "We think that is not true." Instead, PlayMedia believes a hefty portion of WinAmp is just a repackaged version of its AMP software. PlayMedia was quick to quash any speculation that it was acting against MP3, vilified by the music industry as the music pirates' format of choice. "I want to be clear that this suit has nothing to do with MP3's intrinsic legitimacy as a format for the playback and enjoyment of music," said Brian Litman, CEO of PlayMedia, in a statement. In October, the Recording Industry Association of America (RIAA) filed suit against multimedia hardware maker Diamond Multimedia Systems Inc. alleging that the company's portable MP3 player, the Rio PMP300, threatened their copyrights. A court weighing the preliminary injunction against Diamond disagreed. The PlayMedia suit raises the spectre of the music industry's claims. Computer software is protected as intellectual property under the Computer Software Act of 1980. NullSoft will seek action against PlayMedia, it said in the statement. Take me to the MP3 Special