20 more technical terms every Mac user should know

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Audio formats

The audio world hasn’t escaped the alphabet soup of acronyms. You’re sure to encounter a number of these audio formats on the Mac as well as on the Web.

AIFF (Audio Interchange File Format): Audio files broadly come in two flavors—compressed and uncompressed. Compressed files are usually missing data that you can’t easily hear (though if you compress a file enough, you’ll certainly hear the difference). Uncompressed audio files reproduce the audio without performing tricks to remove data. They are therefore larger than compressed files.

AIFF files, which were originally developed by Apple, are uncompressed. AIFF files are supported by iTunes and used by professionals and others who seek the highest audio quality.

WAV (Waveform Audio File Format): This is another uncompressed audio file format. It was developed by Microsoft and IBM, and is more commonly found on Windows computers, though Macs can use them as well.

iTunes supports the most common audio formats.

MP3 (MPEG-1 or MPEG-2 Audio Layer III): MP3 files are compressed, and were quite popular in the early days of digital music because of their reduced file size. They continue to be used quite commonly today by many music services and devices. QuickTime, iTunes, and the Mac support MP3.

AAC (Advanced Audio Coding): AAC is another lossy compression format and one that’s gaining popularity. It’s the format for music you buy from the iTunes Store, and it’s Apple’s default format for encoding music within the iTunes application. AAC is widely used in other settings as well—on YouTube and in Nintendo DSi and PlayStation 3 game consoles.

AAC has gained popularity because it’s believed to produce better-sounding audio files at lower bit rates (the number of bits processed over time—the higher the bit rate, the better the sound, but also the larger the file). AAC files on the Mac are generally denoted by their .m4a extension. Tracks purchased from the iTunes Store that are copy protected (Apple dropped copy protection a few years ago) have a .m4p extension.

Apple Lossless: Although the name says “lossless,” these files are compressed (don’t ask). The resulting file size is between 40 and 60 percentthe size of the original uncompressed version and sounds indistinguishable from it (cue the audiophiles). Apple Lossless is supported by the Mac and OS X as well as by iOS devices.

WMA (Windows Media Audio): This is Microsoft’s lossy compression audio format. It’s not supported at all on iTunes for the Mac, though the Windows version of iTunes will convert WMA files to MP3 or AAC format for compatibility with iOS devices. At one time WMA files littered the Web, but because they’re not compatible with many of today’s devices, you see them less often.

Video formats

As with audio, video formats abound as well. The Mac supports the most common ones. They include:

MPEG-4: This is a broad standard that defines methods of video and audio compression. There can be variations in the MPEG-4 files you encounter, and these variations are based on the “part” designation. For instance, MPEG-4 part 2 uses a variety of codecs (which stands for compressor-decompressor)—technologies that compress and make movies playable on a variety of devices. Part 2 codecs tend to be older and are used in DivX, Xvid, 3ivx, and Apple’s QuickTime 6 technologies.

MPEG-4 part 10 is more modern and uses H.264 encoding, which produces smaller files that still look quite good. Today’s iTunes and QuickTime—and applications that rely on QuickTime (iMovie and Final Cut Pro, for example)—are compatible with the H.264 standard. Videos you find in iTunes usually bear the .m4v extension, indicating that they’re compressed using this codec.

QuickTime movies: QuickTime is far more than just an application or the engine that iTunes uses to play videos. It’s a layer of the Mac operating system that handles many of the Mac’s multimedia chores. In this discussion, however, we’re talking about the .mov files that QuickTime produces. QuickTime movie files are containers. And by that I mean that they can take advantage of a variety of codecs. You can, for example, create one QuickTime movie that uses the H.264 codec and another that employs Apple’s ProRes codec, yet both can have the .mov extension.

As a container, QuickTime supports a wide variety of codecs.

The important thing to know is that files that bear the .mov extension can almost always be played with QuickTime Player and iTunes. You must convert them before you can play them on an iPod or iOS device, however, as these devices don’t natively support .mov files.

AVI (Audio Video Interleaved): This is another movie container format—one made by Microsoft. Thanks to the more-universal MPEG-4 variations, AVI movies are disappearing from the Web.


You can’t throw a brick at the Internet without hitting yet another arcane acronym. And because you can’t, this series could go on forever. But it won’t, because, FWIW, YAIHBWTSOT (You And I Have Better Ways To Spend Our Time.)

One of those ways is for me to take a vacation. Class dismissed until July 25th!

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