iTunes Encoding Strategies
Building a digital music library used to be a simple matter of inserting a CD into your computer and encoding the songs as MP3 files. Today the process is a little more complicated. iTunes 4.5 and later not only supports the popular MP3 format but also gives you the option of encoding files in the AAC (Advanced Audio Coding) format or in a new format called Apple Lossless. So which one should you use?
Each format offers a different compromise between file size, sound quality, and compatibility. The key to picking the right format for your digital music library is to find the compromise that best suits the way you listen to music. Here’s a look at the current encoding options built into the most recent versions of iTunes and the situations that call for each one. I’ll also examine options for converting songs from one format to another.
If Size Matters
As your music library grows, the amount of disk space it requires may become an issue. When you want to use disk space efficiently and fit as much as possible on your iPod, your best bet is to use one of the two lossy audio formats: MP3 and AAC.
An MP3 or an AAC file isn’t a bit-for-bit duplicate of a digital recording; instead, it’s a very accurate approximation. When you rip a CD into one of these formats, iTunes analyzes the recording and discards portions of it that most of us can’t hear anyway. This deliberate lessening of quality makes MP3 and AAC files roughly one-tenth the size of the original tracks on a CD.
Of the two formats, AAC is more efficient—it allows you to encode at a lower bit rate and still get excellent sound. For example, an AAC file encoded at 128 Kbps generally sounds as good as an MP3 file encoded at 160 Kbps, but the AAC file uses less disk space (AAC and MP3 use different criteria when deciding what information to discard).
By default, iTunes encodes AAC files at 128 Kbps and MP3s at 160 Kbps. However, you can specify a different bit rate by opening iTunes’ Importing preference pane and selecting Custom from the Setting menu. For example, some users prefer the sound of AAC files encoded at 160 or 192 Kbps.
If Sound Matters
To my ears, MP3 and AAC files sound great. But golden-eared audiophiles cringe at the notion of compromised sound quality. For these users, Apple created the new Apple Lossless encoder.
True to its name, Apple Lossless doesn’t discard any audio information when encoding. As a result, Apple Lossless files sound truer to the originals, but they don’t use disk space as efficiently as MP3 or AAC files. Apple Lossless files are roughly half the size of the originals—several times larger than their MP3 or AAC equivalents. This may be a problem if you’re trying to shoehorn a large music library into an iPod mini.
In fact, even if you have only a small music library, Apple Lossless files may not be a good option for listening to music on your iPod. The large files cause the iPod’s hard drive to spin up more often, requiring more-frequent battery charges.
With drawbacks like these, why use Apple Lossless? One reason is sound quality: if you have good hearing and good audio equipment, you will be able to tell the difference. High frequencies have more sparkle while bass lines sound less muddy.
Another reason to use Apple Lossless is to hedge against format obsolescence. If you ripped hundreds of CDs into MP3 files a few years ago, you’re stuck with relatively low-quality files unless you rerip the CDs. By using Apple Lossless, you can build a digital music library that won’t make you cringe as your listening skills and equipment improve. Indeed, this is the reason some serious audio buffs use the AIFF or WAV format to encode their CDs—these uncompressed formats don’t affect sound quality. Unfortunately, they also gobble up about 10MB of disk space for every minute of music—not exactly ideal for storing thousands of songs.
If Compatibility Matters
Having great sound is important, but it won’t do you much good if you can’t play your music. Newer encoding schemes such as AAC and Apple Lossless don’t have the wide support that the MP3 format has. So they may limit you in terms of what you can do with your music outside of iTunes and the iPod.
Every iPod can play MP3 and AAC files (older iPods need a software update for AAC). But Apple Lossless works only on iPods with a dock connector. If you use a non-Apple MP3 player, you’re even more limited: they don’t support AAC or Apple Lossless.
Likewise, many newer car and home stereo systems can play CDs containing MP3 files, making this a great way to store long music mixes for a road trip or a party. But if you burn a playlist as an MP3 CD, iTunes skips over AAC and Apple Lossless tracks.
You can detour around some of these compatibility barriers by taking advantage of iTunes’ ability to convert between audio formats.
Unprotected AAC to MP3 To make a copy of an AAC file that you can play on a third-party MP3 player, open iTunes’ Importing preference pane, and select MP3 Encoder from the Import Using drop-down menu. Because you’re converting from one lossy format to another, use the Higher Quality option to minimize further loss in quality.
Next, select the tracks you want to convert and, from iTunes’ Advanced menu, choose Convert Selection To MP3. iTunes creates MP3 versions of the tracks and adds them to your music library.
This process leaves your original AAC files unchanged, so you’ll have two versions of each song you convert. To deal with the duplicates, corral them into a smart playlist with the criterion Kind Is MPEG Audio File.
Protected AAC to MP3 Creating MP3s from music you’ve purchased at the iTunes Music Store is trickier. iTunes won’t convert a purchased song—doing so would strip the song of its copy protection. To work around this limitation, burn the protected songs to an audio CD, and then rip the CD into MP3.
Conversions to Avoid Incidentally, there’s no point in converting an MP3 or an AAC file into Apple Lossless format. You can’t create a lossless audio file from a lossy version any more than you can re-create a complete novel from a Reader’s Digest condensed book. Similarly, there’s no reason to convert an MP3 into AAC format. MP3 has the compatibility edge, and the sonic damage that a conversion would impose wouldn’t be worth the slightly better storage efficiency.
Build a Master Library
If disk space isn’t a major concern for you, and if you have enough patience, you can use iTunes’ conversion tools to get the best of both worlds: maintaining a master music library in Apple Lossless format, and then creating lossy versions of tracks for your iPod.
Start by ripping your CDs into Apple Lossless format. When you want to move some selected tunes to your iPod or other MP3 player, set your Importing preferences to the correct format and choose Convert Selection from the Advanced menu. Put your iPod in manual-update mode to avoid also transferring the Apple Lossless versions. Then drag the newly converted files onto the iPod icon.
You can delete the converted files after transferring them, or, if you want to keep them for future use, create a smart playlist to help keep track of them.
To Each Its Own
Although I’ve focused on the encoding options built into iTunes 4.5 and later, there are plenty of other encoders on the market, such as FLAC and Ogg-Vorbis, and they have their own loyal followings. In fact, the encoder showdown feels almost like a replay of the Betamax-versus-VHS wars of the 1980s. Thankfully, there’s almost always a way to convert music from one digital format to another.