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Create it
So how do you get down with digital audio? You probably already have a ton of music, but converting your existing CD collection into a digital audio library is thankfully simple. You need a PC, a CD-ROM drive, and some software.
In the jargon, a software application that copies and compresses audio tracks is called a ripper. It extracts the music from a CD as a.wav file--an uncompressed copy of the song. Each minute of uncompressed audio takes approximately 10MB of space on your hard drive. To shrink the file size, your PC uses a codec (short for compressor/decompressor) to compress the sound.
The codec determines what information can be omitted to make the file smaller. The human ear can't hear every frequency; through a science called psychoacoustics, the codec removes bits that you would never hear to create a more manageable file size. Some people claim that they can distinguish compressed audio from uncompressed. See the "Compressed Audio Test Report" sidebar below for details of our tests on the four major audio codecs.
A compressed file's size depends on how much compression you apply; this compression is generally described as a playback bit rate. If you choose a high bit rate--say 320 kilobits per second--the file will be bigger, and less audio data will be taken out. If you pick a low bit rate--96 kbps, for example--you'll get a much smaller file, but the compression may cause noticeable aural defects (for more on the inner workings of MP3 compression, check out "How it Works: MP3"). Coding Technologies of Sweden has come out with a new format, called MP3pro, that is supposed to sound twice as good as standard MP3 (see "MP3pro Offers Better Sound in Less Space"); unfortunately, however, portable players that support this format are not yet available.
Popular applications that can rip and encode digital audio include Audiograbber, MusicMatch Jukebox, and RealJukebox. You can download free versions of the last two, but the pay versions speed up the encoding process and give you more control, so upgrading to them is probably worthwhile. For example, MusicMatch claims that the commercial version of MusicMatch Jukebox can rip music 25 percent faster than the free versions and can burn to CD-R discs at higher speeds.
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