Apple iPod portable music player Page 2
Parts choices are said to have been made with an emphasis on sound quality, availability, and "time to market" considerations. Parts vetted include PortalPlayer's own MP3 decoder and controller chip, a Wolfson Microelectronics D/A converter, a Sharp flash-memory chip, Texas Instruments' IEEE1394a interface controller, and a Linear Technologies power-management and battery-charging system. The essential innard is the hard disk drive (HDD), which is amazingly tiny—a 1.8" Toshiba design built to fit Toshiba's PCMCIA cards.
The iPod's PCB is a marvel of parts density—so much so that I was almost completely at sea when confronted with it. The largest item, by far, is the Sony-Fukashima lithium-ion battery, molded to fit over the HDD. The back of the circuit board is dominated by the LCD display and the controls, which are attached directly to the board. The board's landscape is dominated by three large chips, presumably the buffer, CPU, and FireWire controller (the only item I'm sure of, since it's next to the 32-pin input). The rest of the board is jammed with surface-mount components.
What are you going to play?
The iPod can be used as an external hard drive for Apple computers—in fact, that's how it shows up on a Mac desktop—but its OS and Apple's iTunes4 software are what distinguish it as an MP3 player. PC users can't use iTunes4, so the CD that comes with the iPod includes MusicMatch software as well as iTunes. iTunes4 is available as a free download from Apple's website. In addition to supporting the iPods, iTunes4 includes several features not available in older versions of Apple's music-management software.
Some of these—such as music streaming, Shared Music, and cover artwork display—are interesting enough, but not germane to a discussion of the iPod's sound quality. The two biggest changes from older versions are linked. One is access to Apple's iTunes music-download website, not currently available to the 90% of computer users who use PCs. The other is the ability to "rip" music in MPEG-4 auto audio coding (AAC) format as well as MP3. (See Sidebar, "Bottom Liners," for details on how this relates to the iTunes website.)
MPEG-4 AAC (ISO/IEC 14496-3, Subpart 4) builds on MPEG-2 AAC's compression technology for data rates greater than 32kbps; at lower data rates, it employs additional tools that augment MPEG-2 AAC, adding scalability and error-resilience characteristics. AAC incorporates temporal noise-shaping, backward-adaptive linear prediction, and enhanced joint-stereo coding techniques. Apple included AAC in its QuickTime 6 software for a variety of reasons, but lists audio quality as the most important of them, citing the many advances in perceptual audio coding and compression that have been achieved in the decade since MP3's development. Apple says, "AAC takes full advantage of these advances, resulting in higher quality output at lower data rates, allowing even modem users to hear a difference."
Ah, modem users...Surely one of AAC's big selling points is its ability to improve compression, packing higher audio quality into smaller files. And, given the tiny size of the iPod and its battery, increased power-management efficiency didn't hurt, either—less processing power is required for decoding AAC files. Additional AAC hot buttons include support for multichannel audio of up to 48 full-frequency channels, and higher-rez sampling rates (up to 96kHz!).
The iPod supports several other audio formats in addition to AAC and MP3, including Audible (designed to download spoken-word files from audible.com, variable bit-rate (VBR) MP3, Audio Interchange File Format (AIFF), and WAV. (All of this choice is available only to Mac users—those syncing their iPods to PCs have to make do with MP3.)
The high-resolution ripping option is AIFF (so closely associated with Apple that some wags insist it stands for Apple's Interchange File Format). The format creates files that contain the raw audio data, channel information (monophonic or stereophonic), bit depth, and sample rate, as well as application-specific data areas, which allow different applications to add information to the file header that aren't removed when the files are processed by other applications—a feature of greater interest to folks who create music on their computers than to those of us transferring pre-recorded music to our storage media. In other words, AIFF is a memory hog, but it's an audiophile's kind of memory hog, since it throws away no data in an attempt to compress the file size.
But iTunes4 does more than rip recordings to stored-file status; it also organizes your music collection and allows you to arrange it into playlists. And it transfers all or any portion of your ripped files to the iPod—a process that's astonishingly fast, thanks to the IEEE1394a connection.
Using iTunes4 is stone simple. It's just as easy to use and intuitively simple as all those raving Apple enthusiasts claim. At least, I think so. As someone who has only recently purchased his first Apple computer, I have grown used to the MusicMatch music-management software, and my memories of learning to use that software have grown so dim that it seems second nature to me now. iTunes4 has a few foibles that differ from the way MusicMatch does things, but I won't swear they're less intuitive, just different from what I've grown used to. Except for one thing: Music Match automatically accesses the CD Data Base (CDDB) for CD and track information when you insert a CD in the disk drive; in iTunes4, you have to pull down the Advanced menu on the toolbar and click "Get track information" (footnote 1). If that strikes you as a trivial inconvenience, we're on the same wavelength.
Footnote 1: Our thanks to reader Gordon Neault, who reminded us that to access the CDDB database automatically on a Mac, you launch iTunes, go to iTunes: Preferences: General, and click the box at "connect to the Internet when needed." The iPod "is a music player an audiophile can love," summed up Mr. Neault.—John Atkinson