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Choosing the Right File Format for Your Digital Music

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MP3, AAC, WMA, or FLAC? Lossy compression or lossless? Low bitrate or high? These are all important questions when ripping your CDs and building a big digital music library. In this article, Ultimate Digital Music Guide author Michael Miller walks you through all the options and helps you decide which is the right file format for your digital music.
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When you’re building a digital music library – via either downloading or ripping from CD – you have some choices to make. First and foremost is the file format for your digital collection; which file format you choose determines, to some extent, which music player apps you can use, which portable music players or smartphones you can buy, and which music player hardware you can install. That’s because not every app or device is compatible with every available file format; rip your music in the wrong format and it won’t play on your iPhone or Sonos music player.

Part of the file format decision includes whether to go with lossy or lossless compression, and which bitrate to employ. There are compromises to be had; which is more important to you, audio quality or file size? Go with superior sound quality and you might not have enough storage space for your entire library. Go with smaller file size and your ears may notice the difference.

Which file format, compression, and bitrate should you choose? It depends to a large degree on what’s most important to you – and which compromises you’re willing to make.

Choosing Between Lossy and Lossless Compression

Let’s start with the issue of compression, because that drives the file format choice. Why is that? Because some file formats use lossy compression, and some use lossless compression. You have to make the choice between lossy and lossless to determine which file formats are available.

Some of you are no doubt wondering what this lossy/lossless stuff is. Well, it’s all about file size and audio quality – two issues that go hand in hand.

Uncompressed audio, such as what you have on a physical CD, results in very large file sizes. Think about it; a typical ten-song compact disc takes up between 350MB and 400MB of storage space. Now, there’s more than enough room on a CD for those ten track (you can store up to 800MB on a single CD), but that’s not the case with other storage media.

In particular, if you tried to store your entire music collection in its original uncompressed format on your 16GB iPhone, you’d run out of space somewhere around album number forty. It’s even an issue on personal computers; even though most new PCs come with 500GB (or larger) hard drives, if you have a very large music library, you’ll eat up that storage space sooner rather than later.

The solution, of course, is to compress audio files so that they have significantly smaller file sizes, and thus take up less storage space. The type and degree of compression used determines how much space savings you get.

Unfortunately, the compression you use also determines the resulting sound quality of the audio file. The more compression you use, the lower the fidelity. So if you need really small files (which you do for smartphone use), you end up with severely compromised musical playback. If you want to preserve some semblance of the original sound quality, then you have to use less compression – which produces larger files. Like I said, it’s a compromise.

When it comes to compression, then, you have three choices:

  • No compression. As you no doubt figured out for yourself, an uncompressed file offers the best audio quality – but at very large file sizes. This is not an option for most people.
  • Lossy compression. Lossy compression works by sampling the original audio file and removing those ranges of sounds that the average listener presumably can’t hear. This approach creates the smallest file sizes, but at noticeable degradation of audio quality. The amount of degradation depends on the type of compression used, the amount of compression used, and the bitrate at which the audio file was recorded. You’ll probably be forced to employ some form of lossy compression if you’re storing your music for playback on an iPhone or other portable device.
  • Lossless compression. If you care about audio fidelity, lossy compression just doesn't cut it. No matter high the sampling rate or how good the compression algorithm, lossy files don't sound quite as good as the originals. For serious music lovers, lossless compression is a better compromise in terms of audio quality vs. file size. Lossless audio compression works more or less like traditional computer ZIP compression; redundant bits are taken out to create the compressed file, which is then uncompressed for playback. So what you hear has exact fidelity to the original, while still being stored in a smaller-sized file. Of course, a lossless compressed file isn't as near small as a file with lossy compression; while a lossy file might be 10% the size of the original, uncompressed file, a file with lossless compression is typically about 50% the original's size. This is why lossless compression isn't recommended for portable music players, where storage space is limited – although it works just fine if you’re storing your library on a computer’s hard disk. (You can easily store 1,000 CDs on a 300GB hard disk, using any lossless compression format.)

So if you have all the disk space in the world (which you probably don’t), going the uncompressed route obviously yields the best sound. If disk space is at a premium, however, you want to go with some sort of lossy compression and accept the lower audio quality. And if you care about both sound quality and file size, consider some sort of lossless compression.

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