I keep seeing reference to iPods failing to play LAME-encoded VBRs properly. Is this a universal problem? My wife recently bought an iPod (4G, 20GB), and is using the same MP3 files that I had already prepared for my Rio Karma. They were encoded with ABR (which produces VBR files, right)? But she's never mentioned skipping problems.

As far as I understand, the newer iPods use very aggressive dynamic downclocking of the playback CPU, and cannot handle the sudden bitrate boosts in some LAME files.

ABR files are less likely to have big jumps in bitrate compared to VBR. With ABR, the bitrate does vary, but it varies around a specific average level, rather than purely varying in response to complexity of the encoded audio signal. Hence, iPods with this issue (for the reasons that Garf described) are less likely to have trouble with ABR than with VBR.

OK, thanks for the info. I use ABR in order to make space requirements rather more predictable, given the limited 20GB space available in both my Karma and my wife's iPod. Seems like perhaps as a lucky side-effect, these files will behave on the iPod.

Garf's description of reason for the problem is interesting. It suggests that it isn't just LAME-encoded files that will have the issue - presumably other VBR encoders will produce equally variable bitrates. Or is LAME radically different in this respect?

Also, am I to understand that this downclocking is how Apple have achieved improved battery life - by making their players even more compromised than they already were? Wouldn't surprise me if that's the case.

It must only happen on certain models, because I have lots and lots of LAME --aps files on my 3G iPod, and it plays them without any issues. I've never heard any skipping or pausing or anything like that from mine.

So this problem seems confined to newer units, I suspect.

The new ARM chips probably use a very aggressive power cycling feature which I guess is to blame here. The old iPods don't have this "feature", but their battery life suck

While this is true with factory gear, you can get a 2200 mah battery replacement made by "NuPower" for 1st and 2nd gen iPod models. Reports say that 20+ hours of battery life is not uncommon. I've not seen batts that big for any of the later models though.

The skipping issue is extremely inconsistent, I don't think anyone's found a sample that skips on all iPods of a given generation.

I hope the 20 GB 4th gen (color screen) model doesn't have this problem, I just bought one.

Do you mean the iPod nano?
U might wanna check on this...

Well, my Ipod has arrived, and yes it has the VBR problem
But the putting on the EQ trick works
Hopefully they will recognize this problem and one day do something about it, MP3 VBR is in the specs so they should do something about it!

Apart from this, I'm very pleased with it and also with foo_pod, I don't want to use more than one player.

As I understand it...the problem that people have reported with VBR files happens soley on the iPod mini & Nano models. I have a 3rd gen 20 gig iPod and almost every file on it has been encoded with LAME APS (VBR) and I have never had any problem with playback. In fact the sound quality is pretty damn good (IN MY OPINION!!!).

On a side note, my niece just got an iPod mini and I uploaded a few CDs to it that I had encoded with LAME 3.96.1 APS and I had no problems listening to those mp3s at all. So, I have never experienced any problems with the several iPods I've tried out.
J

Edit: Typo & I always have the EQ enabled on my iPod to enhance sound output. Not sure if that has any effect on the skipping problem people are reporting though.

Nope 4th gen ipod's 20 (and probably 60) GB with color screen also have the problem.