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I've recently been involved in a round of returns/repairs with Apple for a 20 GB iPod centering around an issue that is common to all models, including the new ones... but an issue that Apple has conveniently avoided mentioning, and instead taken misleading approaches when dealing with it.
This is a problem that not many people will encounter, but can be very annoying to those who do. When playing an uncompressed audio track (WAV or AIFF) from an iPod, it will stop every 2 minutes and 17 seconds for a few seconds, then continue playback... For another 2:17.
WAV and AIFF playback is supposedly supported: Audio formats supported: - Mac: AAC (up to 320 Kbps), MP3 (up to 320 Kbps), MP3 Variable Bit Rate (VBR), WAV, AIFF, Audible (Mac only) - Windows: MP3 (up to 320 Kbps), MP3 Variable Bit Rate (VBR), WAV [from Apple's iPod spec sheet] so what's the deal here?
The explanation: 2:17 of stereo 44.1kHz, 16-bit audio (what's encoded on a regular CD) is nearly exactly 24 MB... It seems that this is the size of the RAM cache in the iPod (it's actually 32 MB, but the other 8 are used for the system and temporary data, such as volume and EQ settings).
Apparently, what happens in the iPod is that it reads 24 MB at a time off the hard drive into the RAM cache, and then shuts down the hard drive (to prevent skips and save battery). Understandable and reasonable. However, here's the clincher - it only spins up the hard drive and refills the RAM cache AFTER it's emptied.
Rather than doing a refill at say 23 MB or so, giving you a seamless playback, they wait until the buffer is completely used, and then they dump it and do a full refill.
Most people won't notice this issue, since at 160 kbps MP3, you've got 25 minutes before the RAM buffer needs refilling, and a two second skip every 25 minutes is not noticed by most people (particularly since most people will skip to a new song at some point in there, thus resetting the buffer).
However, we've got a couple of misleading things here: Apple never actually lists what the RAM cache is. Instead, they list 'up to 25 minutes of skip protection', without
mentioning what the rate used for that is - it could be much more, if you're using mono 32kbps.
Second misleading point is calling it 'skip protection' at all. The other place that term is encountered is in portable CD players - which read-while-writing to the RAM buffer, and have ever since the beginning (back when the RAM buffer was only 5 seconds or so).
Third misleading point is the statement that the iPod supports AIFF and WAV playback... when they should specify that that's only if your files are under 2 minutes in length.
The iPod is still a good piece of hardware, but this cuts down its usefulness as a high-quality playback device, and should be noted by anyone interested in purchasing one for professional playback. Incidentally, none of this is mentioned yet anywhere on Apple's knowledge base.
UPDATE: Reportedly, this is fixed in Gen 3 iPods. I'm going to buy one and see.
I'm a 24 year-old audio engineer currently working in the broadcast industry, with 11 years of professional experience within the audio industry (including studio recording and sound reinforcement). I'm the assistant chief engineer of a decent-sized radio group that serves as the NPR outlet for two major market cities. My work is mainly repair/maintenance of electronics, audio gear, and transmitters.
It's the most low-stress job I've ever had.
Aside from the fact that they're a rich non-profit and they pay well, they also appreciate me and my skills as a talented problem solver who can rush in and put out fires before they grow too large. Every day, I get to point to something (or several somethings) and say "I fixed that. It is better for my having been here." While the money is nice, that sense of accomplishment and respect (both self- and from other people) is highly valuable.
If you have any questions regarding audio, electrical engineering, RF, radio/television/film, production, or music, feel free to ask. If you have any opinions regarding politics, religion, or philosophy, feel free to debate.