The decade-old MP3 digital sound recording format has been updated to become MP3pro. Pro now has double the compression rate of MP3 at the same sound quality.

Thomson and the Fraunhofer Institute, creators of the MP3 format, released a coder and decoder (codec) for the MP3pro format yesterday. For more information click here.

The new release achieves "parity or better" in terms of quality with the Windows Media Audio 8 format developed by Microsoft said Dave Arland, spokesman for Thomson.

MP3pro "dramatically improves sound quality in terms of bit rates," Arland said. An MP3pro file carries near CD-quality sound recorded at 64Kbps (kilobits per second), about equal to that of the Windows Media Audio version and about half the file size required for the same song in the standard MP3 format.

An MP3 music file recorded at 128Kbps (kilobits per second) will take up around 1MB (megabyte) of sound per minute. The new codec allows recordings of two minutes per megabyte without losing fidelity.

The original MP3 codec discarded some high pitch sounds in order to prevent encoding errors at low bit rate recordings, Arland said. The result sounded more like a tape recording than a CD, he said. An MP3pro recording uses two tracks, one like the old MP3 and another just for high-frequency sounds. The MP3pro "improves the high-end frequency response... the higher pitches are more distinct", explained Arland.

The new codec is backwards-compatible with MP3 players - an MP3pro player will be able to play MP3 files. However, existing MP3 players will have some trouble with high-pitch sounds on MP3pro files because the old readers won't play the secondary high-frequency track.

About 12 million portable devices and 250 million personal computers have an MP3 player, Thomson estimates. The firm is negotiating with several companies to use the new format in portable players and music download sites.

Windows media files carry digital rights management (DRM) protections, preventing unauthorized copying. MP3 files do not, and neither do MP3pro files, for now. One reason MP3s have outpaced the popularity of other formats has been the lack of copy protection, leading to bitter fights between music publishers and file swapping sites such as Napster, Windows Media Audio and RealNetworks.

MP3 has become synonymous with music on the internet - as well as synonymous with music piracy. "I think content restrictions are going to be a way of life," Arland said. "There's nothing to say that we can't add DRM [digital rights management] later. It's easy to do." Thomson had considered adding DRM capability to its first version, but chose to wait.