The digital audio standard that changed the way many of us listen to music will soon undergo a change of its own.

Thomson Multimedia has announced an improved MP3 codec called MP3pro that purports to double performance - storing more music in less space, in tune with Microsoft's competing Windows Media audio standard.

Under the new codec (compressor/decompressor), a song recorded at 64 kbps will sound the same as one recorded under the old MP3 at 128 kbps, says Rocky Caldwell, a Thomson spokesperson.

In other words, for half the storage space you'll get the same quality. Programs and devices that use the new MP3pro codec will also continue to play existing MP3s.

Caldwell expects the new codec to begin appearing in PC-based MP3 applications within the next few months, and to appear in handheld MP3 players soon after that.

Thomson shares the patent rights with the Fraunhofer Institute, and it handles licensing of the technology, according to Caldwell. A Fraunhofer spin-off company called Coding Technologies developed the new MP3pro codec.

It's the portable devices where the improvements are most likely to be most appreciated. That's because most of today's handheld players have limited amounts of built-in storage, and adding more can be pricey.

Under the current MP3 standard, 32MB of storage gives you less than 30 minutes of play at the near-CD-quality compression rate of 128 kbps. Recording music at a lower compression rate such as 96 kbps requires less storage space but sacrifices audio quality.

Soon, a 32MB player that supports the new MP3pro standard will offer about an hour of music (recorded at 64 kbps) that sounds just as good as the previous MP3 recording at 128 kbps, according to Caldwell.

Microsoft claims its existing WMA standard - supported on a growing number of players - already provides an hour of quality music in 32MB.

Most PC-based MP3 application providers such as MusicMatch and Winamp are likely to offer MP3pro with little fuss, as it's simply a matter of downloading the upgrade.

Likewise, RealNetworks' popular RealPlayer already supports a number of formats, including Microsoft's WMA. However, not every handheld MP3 player will support the new standard.

Existing players locked into the MP3 format can't play the new standard. But some players capable of accepting new codecs should be able to use it, according to Caldwell. Thomson's own player, the RCA Lyra, supports both MP3 and WMA standards and will support the new MP3pro as well, he says.

All of Rio's current-generation players are upgradeable, so the company can offer a MP3pro upgrade, notes Jim Cady, president of Rio, which launched the pioneering Rio 300 MP3 handheld player in 1998. But its first-generation players, the Rio 300 and 500, do not support codec upgrades.