How the iPod chokes on large files
That iPods have generally been bad with large files is a fact I have known since 2002 and my second generation 10GB iPod. By "large", I mean an audio file that's 10-30 hours in length - not your average song. All the files of these proportions in my possession happen to be audiobooks. I have never purchased a single audiobook off the iTunes Music Store, but I am not interested in hearing the argument that iPods are only supposed to play those audiobooks correctly which have been bought from the iTMS. That kind of argument would be, in my opinion, tosh.Anyway, political issues apart, here's the problem. On my 10GB 2G iPod, if I attempt to play an audiobook (i.e., an AAC file with the extension M4B) of a length that's around 20 hours or more, the iPod will simply get stuck. I once gave it the benefit of the doubt that it wasn't frozen by giving it the opportunity to get unstuck until its battery died but that was a no-go. However, it worked better with an 11-hour audiobook. By better I mean that it took a while for it to start playing, but it did eventually start and it remembered the playback position (the equivalent of a bookmark) like it was supposed to. Now, on my new iPod nano, I tried listening to the same 11-hour audiobook (which incidentally happens to be Harry Potter and the Prisoner of Azkaban narrated by Jim Dale, a most delightful listen) and although the iPod played it back and remembered where I paused it, the iPod was visibly choking on the file. Screen updates occured once every five to six seconds instead of continuously and any button presses also similarly worked after five to six seconds. This was actually quite annoying and it made changing the volume or scrolling through menus while the book was playing nearly impossible as the scroll wheel requires live action which is extremely hard to do on the five-second-delay model.
Another interesting facet to this issue is the fact that my iPods do not choke on MP3 files of the same lengths because I had converted my AAC version of Harry Potter and the Order of the Phoenix to MP3 and decided to remember where I last stopped listening on my own and the iPod played it back fine.
Now, I don't expect that my iPods are the only ones that have this affliction - I think it's got to do with the way the software works. The problem also seems to get worse as you progress through a large book like Harry Potter and the Prisoner of Azkaban. All said and done, I reported this issue to Apple way back in 2002 and they have done nothing to resolve it four years later. Granted that it is probably an issue that perhaps not too many people will experience, it is nonetheless an issue with the iPod's caching mechanism and needs to be resolved. Also, I do not know if this choking occurs on audiobooks bought off the music store, but since they are supposedly encoded in the same AAC format as my audiobooks, I don't see why it shouldn't occur if the books are of similar lengths.
The shuffle sometimes loses my place after an iTunes sync -- maybe one time in 10 or so -- which can be quite annoying; I now double-check it when I sync.
I encode from CDs, then combine and chapterize the files with Doug's AppleScripts' "Join Together." (A few older ones I converted from MP3s, then combined and chapterized.) I generally use 40kpbs mono or 96kbps stereo, depending on whether it's a straight reading or more of a "performance" with some non-voice elements. One I accidentally did at 256kbps made my 5G choke.
Don't know if any of that helps (it's not the same iPods you have, for starters). But you might try experimenting with encoding rates or with the method you're using to encode the files and see if you can get any better behavior.