Apple iPod Technical Brief
and Usage Tips
Apple’s iPod has really expanded the market for
hard-drive-based portable music players. Major features include storage capacities
starting at 5GB, a compact size, fast file transfers (on and off the device), and
excellent sound quality for a portable player. Since it’s really a small computer,
it’s a fairly complicated device, and this article discusses some of its internals as
well as the computer-related aspects of using it. You’ll see a full review of the
iPod in September.
Sizing up the portables
There are several other hard-drive-based players on the
market right now like Remote Solution's PJB, the Creative Nomad Jukebox Zen, the RCA Lyra,
and the Archos Jukebox. Many of these are cheaper on a per-gigabyte basis than the iPod,
but none is as small. A good table showing some of these products is at www.kentidwell.com/ipod/. As I
write this, the Creative Nomad information covers an obsolete model and the PJB prices are
outdated, but the rest of the information is solid.
Looking at this on a gigabyte-per-dollar basis is
interesting, but misses the point. The iPod is just barely small enough (2.5" x
4" x 0.8") to carry with you easily, while the other players are too big: the
PJB is too long, the Archos too wide and deep. At 3" x 4.5" x 1", the Nomad
Zen comes closest, and it is really the only useful competitor to the iPod in the
"carry it with you everywhere" market. The iPod is also lighter than its
competitors at around seven ounces, versus 10 to 12 for most of the others.
File system
On the inside, a Macintosh iPod is formatted with the HFS+
file system, while the Windows version uses FAT32. What this means in simple terms is that
if you plug a Windows iPod into a Windows system, the unit’s hard drive will mount on
your system in the same way a regular hard drive does. Similarly, the Mac version looks
like a FireWire hard drive to that type of system. Apple’s Mac Software Updater,
available from their website, will convert the hard drive inside a Windows iPod to the Mac
version. They don’t recommend going the other way, but software like that available
at www.the-midfield.com/ipod.aspx
will turn a Mac iPod into a Windows one, and some hackers have done the same thing just by
reformatting the drive using Linux.
Skip protection
The iPod implements skip protection by putting a 32MB
memory buffer in the player. Now, if you’re playing stuff at CD quality, you will
burn through 32MB in about three minutes instead of 20. You’d think that the iPod
would be fine as long as it could read the hard drive every three minutes but,
disappointingly, that turns out not to be the case. The end result is that when playing CD
material, the iPod works about as well as a good CD portable, typically surviving a minute
or two when jostled before it starts to skip badly. The best theory I’ve seen
presented, from www.ipodhacks.com,
is that songs larger than the 32MB buffer aren’t actually buffered at all, and are
played straight from the hard drive.
Transfer speed
The speeds of current CD-ROM drives and computers allow you
to convert a full-length CD into a computer-usable digital form in a couple of minutes.
The iPod connects to your computer using a FireWire port, and with this interface you can
replace the entire contents of a 10GB iPod in 25 minutes.
Many of the other portable digital-audio devices use USB
1.1 as their interface. This tops out at 12Mbps. At that speed, updating 5GB worth of data
is going to take many hours. This was a huge limiting factor that prevented earlier
hard-drive systems like Remote Solution’s PJB from ever catching on. Some of the
newer products support USB 2.0, which ramps the speed up to 480Mbps to match FireWire
capabilities, assuming your computer also has a USB 2.0 port.
Computer-interface software
If you have a matching Apple Macintosh to go with your
iPod, life is easy. Use iTunes, organize your music, and off you go.
On the PC it’s a bit messier. The Windows iPods ship
with a version of MusicMatch Jukebox, an MP3 and music organization program that’s
fairly popular for no reason I have ever been able to fathom. I find the program difficult
to navigate, underwhelming in its support for simple features (try to batch convert a
bunch of WAV files to MP3 with it), and just thoroughly painful every time I touch it.
Before you install MMJB, when you plug the iPod in it will
show up in Windows as a removable media drive. After you complete installing the software
and reboot, the iPod only appears to MMJB, preventing other software that might want to
look at your iPod from working. Fixing this was my first non-obvious task. If it bothers
you, too, get the PortablesPlus interface to the iPod going. Right click on the iPod under
Attached Portable Devices and select the Options item. Under the iPod tab, you’ll
find two settings you need to change from their defaults. "Automatically launch
MUSICMATCH Jukebox on device connection" can be turned off, and "Enable FireWire
disk use" must be turned on for software that wants to see the iPod.
Here’s a typical example of why I hate MusicMatch
Jukebox: I added 9GB worth of WAV files to the program’s media library and told it to
copy them to the iPod. It complained that there wasn’t enough space to hold them all;
this was obviously a bogus warning because it was still there when I reduced the transfer
to less than 1GB. Regardless, once I overrode the warning it started transferring. After a
couple of files, it died. No error message -- it just stopped, for no apparent reason.
My older but reliable computer that I was using for these
tests has a Creative Technology Sound Blaster Audigy in it, and I’ve used the
FireWire port on that system before to throw dozens of gigabytes worth of information
around without a problem. I didn’t know what was happening.
XPlay Windows software for iPod
Finally reaching my level of disgust with MMJB (as I do
every couple of years when I try it again to see if things have improved), I tried
downloading XPlay from www.mediafour.com/products/xplay/.
This $30 program allows Windows computers to use the Windows or Macintosh version of the
iPod. Of course it doesn’t work unless you first do the "Enable FireWire disk
use" trick I outlined above, but after that I could navigate the program.
XPlay replaces the music library abstraction that many MP3
programs use nowadays with a simple mapping of the iPod interface into the Windows
Explorer system. When you double-click on the iPod, it shows the files on its hard drive,
and there’s an XPlay Music folder. Go into this folder and you see the
Playlist/Artists/Songs/et cetera as folders you can navigate into. Find the music
files you want to install on your Windows computer, drag and drop them over to the right
area of the iPod, and you’re done. I only encountered one issue with this interface:
XPlay seems to sort the file names for you before copying them. Sometimes I had to
struggle with the program to get the track order correct when I was copying an album I
wanted to play in its regular running order.
The minute I tried copying files over with XPlay, it
chugged along copying a dozen or so of them, then came back with "CRC Error."
Cyclic Redundancy Check errors mean that some number of the bits were corrupted during the
copy. With this program I could eventually fight through that and get all the files on the
iPod by doing the copy over again. (MMJB isn’t as smart about picking up from where
it left off if a copy aborts.) The nice descriptive error messages XPlay spat out
suggested I try a different computer to see if it was more compatible.
With my second system, a more bleeding-edge setup with
Creative’s newer Audigy 2 sound card, copying files to the iPod worked flawlessly.
The original Audigy was disappointing to me in a number of respects; on the other hand,
I’ve been very impressed with the Audigy 2. Its analog and speaker outputs sound as
good as any PC sound card I’ve ever heard, far better than the original Audigy. Its
price is more reasonable, and the DVD-Audio support is nice as well. I’ve also had
good luck with the iPod and the FireWire ports on the $30 (and sometimes even cheaper)
Inland u-Connect PCI to IEEE 1394 card. It uses Via’s chipset and works fine on both
PCs and older Macs that don’t have a built-in FireWire port.
If you’re comfortable with navigating the Windows
Explorer interface to move files around, I’d say spend the extra $30 to buy XPlay and
use that instead of MusicMaker Jukebox. This is an essential purchase in order to make the
iPod a happy Windows citizen. You’ll need another program to encode music into MP3 if
you go that route, but there are plenty of those available for free (like Winamp) that are
much better than MMJB as well. One of the things that is nice about the iPod design is
that there are some options available in this category. Some other MP3 playback devices
ship with proprietary software to load music into the player (which no one has bothered to
replicate and improve), so if those programs don’t work well for you, you’re out
of luck.
Equalization
The iPod includes a digital equalizer that can come in very
handy. There are 21 presets, some labeled with obvious applications (Treble Booster, Bass
Reducer) and others with intended musical styles (Hip Hop, Latin, and many others). Going
through all of the presets by ear, I was impressed. The way they’re implemented seems
clean -- I never got that feeling that the sound has been torn apart and reassembled,
which comes with your typical analog EQ box, and the frequency-transition curves were
reasonably smooth. Before I went too crazy trying to analyze everything by ear, I found
the following essential charts: www.modeemi.fi/~vesas/iPod_Audio.pdf. This guy hooked his iPod up to
an Audio Precision test station and graphed each of the EQ settings. The ones I identified
by ear as being way too much are clearly shown to be the more extreme settings when you
see their graphs. Rock has a +4dB boost at 20Hz and a +3.5dB peak at 20kHz, making it very
fat and bright. R&B is even worse, at nearly +6dB at 20Hz and +2.5dB at 20kHz. Even
Classical, which on a lot of EQ presets is a fairly benign setting, is +3.5dB at 20Hz and
+2.5dB at 20kHz, relative to its lowest point around 1.5kHz.
I did find some settings useful. Electronic is a relatively
smooth curve featuring +2dB of boost at 20Hz relative to its average, +1.5dB up at 20kHz,
and some shallow dips around 300Hz and 7kHz. Acoustic is also an interesting setting;
it’s +3dB at 20Hz, dropping steadily to -0.5dB by 20kHz, but with a big bump around
3-4kHz that pushes the response level back to the 20Hz level again. The boost around 3kHz
is similar to what HeadRoom does in their amps with the filter switch that some models
(but not the AirHead) include.
Watch out on all the EQ settings when you compare them with
flat. In almost every case, the average volume level goes up 1dB to 2dB in addition to the
larger boosts in specific spots, so a comparison is always going to make the EQ’d
version sound better initially, just because it’s louder. As EQ goes, the digital
setup on the iPod is far more useful than most, with its overall clean-filter
implementation and the existence of some subtle but useful response nudges. If you’re
using a Mac, it’s also possible to tag individual files with their own EQ settings
using iTunes, but I haven’t tested this myself.
iPod hacking
I predict that a year from now, as everyone’s
warranties expire on this unit, you’ll see an iPod upgrade scene similar to
what’s happening with TiVo hacking right now. It should be straightforward to take
apart an iPod and swap a 1.8" hard drive with more capacity into it as they become
available. The lithium-ion battery on the iPod will eventually die out, holding much less
than the ten hours of playtime it offers when it’s new; that could be replaced with a
new unit as well. Tom’s Hardware documents an iPod disassembly and shares similar
thinking on this subject at www17.tomshardware.com/mobile/20021003/ipod-02.html
if you’re curious. It’s also worth noting that Hitachi has already introduced
20GB and 40GB drives in the 1.8" form factor.
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