Supported file formats

While MP3 is by far the most popular file format for digital music, some players also support AAC (Advanced Audio Coding, compression technology part of the MPEG-2 standard) and WMA (Windows Media Audio) formats. Keep in mind that if your player doesn't support WMA, you won't be able to take full advantage of the many commercial music download services that use this format.

AAC and WMA offer better compression than MP3, which means better sound quality and smaller files. This is also the case for formats such as MP3 Pro or the open-source OGG (Vorbis) - both of which have yet to gain much support in the portable music player market.

Until recently, all Sony MP3 players came with software that you had to use to convert MP3s to its proprietary ATRAC standard. Recently they released their first player that offered a simple drag and drop file transfer, so hopefully they continue this trend in the future.

Another thing worth considering is lossless formats. All of the aforementioned options make your music smaller by compressing it, thus losing some of the data. Audiophiles may not be satisfied with the drop in sound quality associated with this, and would prefer to store a smaller number of higher quality tracks. Some options in this area include FLAC, WAV and Apple's proprietary lossless format. Until recently, storing a large quantity on lossless tracks was impossible due to space constraints, but with products like the 160GB Apple iPod classic hitting the market, this is a much more feasible option.

Aside from that, make sure your player can handle files encoded with Variable bit-rate (VBR) and ID3 version 2 tags. Most MP3s also use an ID3v2 tag, which is used to store information about the song, such as artist name, album details and genre.

Some devices will fall over if they encounter MP3 files with this feature, so check that ID3v2 tags are supported by your player. Check also that you can play low bit-rates such as 56Kbps, as well as high bit-rates such as 192Kbps, 256Kbps and 320Kbps.

The best place to do all this checking is the manufacturer's Web site.

There are some portable digital audio devices that don't play MP3 files. If you are interested in any of these, make sure they come with software that can convert your MP3 files to the proprietary format.