What is the best compressed iTunes format?

Yea, I've ripped 500-plus CDs twice, and don't recommend it one little bit. Unless you're either starting from scratch or really biting the bullet for a total conversion to a computer-based source, no reason at all to redo everything. Sounds like you've got the perfect plan. Cheers and enjoy.

Right, three things.

First and foremost: yes, once you rip things lossless, you never have to touch the CDs again. Far as I'm concerned, that's the whole point.

Second, on my version of itunes, when you plug an ipod in, and you then select it from the menu on the left, you get the screen with various tab-like choices on the top to manage what's on the thing ("Summary, Apps, Movies, TV.".. etc.) On the "Summary" tab, there are three areas ("ipod" "version" "options") and the third "option" is "convert higher bit rate songs to 128 kbps AAC." If you select that, it's precisely what it'll do for you when you sync. No fuss, no muss, and a full ipod.

Third, our genuine Remo is of course correct, if you want full auto, 128 kbps AAC is your only option. Typical Apple: you want it easy, it's our way or not at all. But, you can also get itunes to manually make you a copy of any track you want in any other format that itunes supports (AAC, mp3, AIFF, Apple Lossless, WAV -- basically anything but FLAC). How to do this, however, aint obvious.

The itunes "help" file explains it thusly:

To convert a song’s file format:
Choose iTunes > Preferences, click General, and click Import Settings.

In the Import Using pop-up menu, choose the format you want to convert songs to, and click OK to save the settings.

Select one or more songs in your library and choose Advanced > Create [Format] Version.

In the off chance that this made no sense at all, it kinda goes like this. Both in your "Advanced" pull-down menu and in the right click menue for any given track, you will be presented with the option to "Create [blank] Version", where [blank] is the default import setting. In other words, if your default setting is to import AIFF, and you have just ripped your entire library AIFF, this option will very helpfully (and apparently without a touch or irony) give you the opportunity to make another AIFF copy. Lovely.

BUT, and I suspect you may see where this is going, if you change your import preferences (say to whatever bit rate mp3 floats your boat), then this same right click / "advanced" option will then the present you with the ability to make a copy in whatever your new default is. You can then select your entire library (or as many or few tracks as you like) and make a copy of all of it in whatever format you want (just remember to switch your default back before ripping any more CDs, or that's what you'll get from them as well).

To sum up, the Apple way is either their way or the hard way -- but you can usually get the job done.... Personally, I like the easy way (think it's spelled l.a.z.y.), but also because I am fanatical about best possible quality on the full rig, but neither care about nor appreciate any difference once it goes on the ipod. But, if your ears and/or the gear you run the ipad through appreciate the benefit of higher bit rate lossy-ness (and I won't pretend that's a particularly difficult task) then you're stuck doing it the hard way and juggling multiple copies of each track in different formats. Enjoy, and as long as you do, you're of course doing it just right.

My two cents, rip everything lossless. Full stop. Eventually, you will come to regret it if you do not do it right the first time. Whether that is AIFF, WAV or Apple Lossless really dosn't matter -- they are all bit perfect and cross-convertible. Storage is super cheap, get them ripped and archived, and know you have them. As beteen lossless formats, don't know any real sonic difference personally, but AIFF or WAV is thought by some to be better, as both are bit perfect and uncompressed. Apple Lossless is in fact lossless, but compressed to about (I thought) 1/2 the size. I use AIFF, but not sure it's important.

Now, all that said, when you put them on a portable unit (ipad/pod/phone, etc), I always set the synching preferences to automatically convert to AAC (the compression/trimming ratio from AIFF to AAC is about 10:1). This way, you have the benefits of everything archived lossless, while your portable versions -- where the format just ain't going to get you that much of a differnce and putting a premium on quantity over quality makes sense at least to me -- convert automatically. Just to re-tweak the math, let's guess that 500 CDs would run you roughly 300gigs AIFF (think I actually have > 700 just north of 350gigs, but anyway). If you set it to automatically convert to AAC when synching, you can easily fit all 500 CDs on a 32gig ipod. Just saying....

Finally, you could rip things twice and essentially have two archived libriaries on disk someplace -- but it's a lot easier to rip lossless and then have a program do the converting for you. As you can go lossless to more compressed, but not the other way -- just make sure to start with lossless and you only need to rip once. Wether you ultimately keep sets of each or just convert on synching is up to you. (The only practical difference that I am aware of is that synching takes significantly longer if you are also simultaneously down-converting to AAC. 300 gigs could run you over 10 hours, so a good overnight task.) Just my two cents.

I'll double check when I get home, but if I am remembering correctly, when you plug in a device to sync, go to the “General Preferences” (or rough equivalent) tab for that specific device and there should be a radial button to check, towards the bottom third of the page, that says something along the lines of “convert higher resolution formats to AAC when syncing.” Check that, and it will automatically do all of the converting work for you while it syncs. In other words, it's a device-specific setting and is not at all related to your import settings. Hope that helps.

Having two libraries, with a primary lossless and then a smaller copy is also a perfectly sensible way to go. For my usage, however, I've found the auto-converting feature while syncing to be both tidier and easier than maintaining separate libraries (which I've tried and gave up on once I discovered the button to ask the computer to do it for you).

Mysterious stuff, no? No accounting for (or predicting) synergies, daffy combos, or personal taste -- far as I'm concerned. I've got a pair of Grado RS-80s that I use on the AAC stuff through the iPad/pod, mostly to and from work on the subway. Like'em just fine for that, in fact, think they sound surprisingly great. But when I tried the Grados on the home rig (all AIFF, Ayre QB-9, dedicated Headroom Home amp for the cans), it was downright unlistenable. Strident, harsh, painful, even. Plain couldn't do it. Actually, I was entirely floored by how genuinely unpleasant it was. Go figure? (But, then, my baseline for cans is Senn HD-600s with Cardas wires, which have got to be near as dark and syrupy as it comes....).

Anyway, not totally surprised to hear that, at least in some cases, there appear to be significant variances in iPod DACs / hardware. I can attest that the itunes software has been noticeably improving on the sonic end also, for what thats worth. Maybe something driver end? Could also be that the hardware at issue was in fact designed to optimize, balance or otherwise sound best with lower bitrate material? Gosh, I'm really reaching here.... Generally, I always assumed that the differences in sound through an iPod would be dominated by factors other than file format to the point where differences in software format wouldn't be particularly determinative. My basis form this assumption? Well, nothing whatsoever, actually. Just a guess that I've been happy enough to just go with. Anyway, very interesting "hard" results. And even more interesting when it's not what you expected going in. Keep us posted. Cheers.

Way I understand ALAC is that it is 100% lossless, but runs a compression algorithm to reduce file size. Think a self executing zip file that automatically unzips itself in RAM every time you play it, while the disk copy remains compressed. FLAC, I think, is similar, but with a variable, user-selectable compression ratio (from 0 to more), whereas ALAC is the Apple version, which invariably means two things: compression ratio is fixed because Apple picks it for you and FLAC not supported on Apple. (And by "fixed" I mean not user-adjustable, I think the compression ratio on ALAC is very variable, just adjusted in secret by the Apple tech boffins and their sneaky algorithms depending on the nature of the track. Again, think zip files – depending on the nature of the file and density, it will be more or less compressable).

The only theoretically possible source of sonic difference between ALAC and an uncompressed lossless format (AIFF / WAV) is the processor burden of uncompressing the ALAC files every time you access them. Once upon a time, that may have mattered more, but with current processors I expect it really doesn't. (Although folks do still argue about it.)

Finally, the explanation for different bitrates on lossless files that has made the most sense to me is that all the bitrate represents is filesize divided by length of the track (kbps, kb/s, to be precise). So, if you compress a track, making the file size smaller, it will read as having a lower bitrate as against the same track uncompressed. But lossless / bit perfect is just that, compression or no, so the bitrate stat for a lossless track is really pretty much meaningless. Put differently, track density or complexity may well have an impact on the compression efficiency and ratio, so there's your source of variability, but all bitrate represents is that result (compressed file size) divided by length. Nothing to lose sleep over.

Flip side, when you pick a bit rate as the controlling factor for track compression – rather than anything to do with the track itself -- it’s kinda like the tail wagging the dog. You’ve imposed an arbitrary variable, mashed the track through it, and then discarded everything else so that your pre-determined kb/s = X equation comes out to equal X. What’s left is only what wasn’t lost, ie deleted, in order to make this arbitrary number (and hence the opposite of lossless). This, in turn, is I expect why “variable bit rate” makes sense, cause it gives the algorithms “discretion” (flexibility?) to take the nature and complexity of the track into account, from second to second adjusting bit rate in accordance with what is actually going on, instead of just hacking and slashing to make an arbitrary number – but in such a way to come out with an average “X” result to meet the predetermined outcome. (OK, that last one was pure guesswork.) So, for ALAC, bitrate is an arbitrary number, but a meaningless arbitrary number. While, for a loss-y format, bit rate is still an arbitrary number, but a fantastically meaningful one because it is what was chosen to determine how much of the original lossless file survived.