MP3 or AAC: Optimum setting for importing audio into iTunes?

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Joined: 02/12/2009

[edit 5/2009: Starting in iTunes version 8 for Mac, the settings described below are located in this menu: iTunes/Preferences/General/"Import Settings". In iTunes 7 and earlier, it's here: iTunes/Preferences/Advanced/Importing. ]

[edit: see the next post for a more complicated way to get even better quality.]

What's the optimum setting for importing audio into iTunes? In general, AAC sounds better than MP3 at equivalent rates, but MP3 is more widely compatible. Whether you pick MP3 or AAC, here's my opinion for the best settings:

mp3 settings
AAC settings

Before explaining, let me first say that I don't care about keeping filesizes small. Big files are fine by me because audio quality is most important (as long as the format is compatible with your software and hardware). If you're trying to fit 100,000 songs on an iPod you may disagree. But let me suggest that you can get the best of both by rotating your collection with smart playlists. Here's how. Then, you can keep your audio quality higher.

If you only use iTunes, and you have hundreds of Gigabytes of hard drive space, you could step it up to the Apple Lossless encoder. These files are huge but next to perfect. But they won't play in most other players beside iTunes and iPods.

No matter which format you pick, dial it up to the maximum kbps setting. It's doubtful that you'll run out of hard drive space much sooner than with a lower setting. But if you do, it's worth it. By that time, you might have a new computer anyway, and the next generation will have even bigger drives.

Another good argument for picking the highest rate available is to future-proof your collection. If you pick a low rate, don't come crying to me when you realize that you need to rip all your CDs again. Of course, it's inevitable that new developments will force you to convert your collection someday, but a higher rate will forestall that for longer. If you keep your CDs after they are ripped, mark them with a sticker indicating the date they were ripped and to what format/rate, (example: 1/1/2004, 320kMP3) because you'll someday need to do it again.
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I used to turn OFF "Variable Bit Rate" encoding (which results in Constant Bit Rate or CBR) because a few years ago some encoders didn't do VBR well, and some very old MP3 players couldn't handle VBR. But recent developments have changed my mind. VBR allows more of the original audio data to be retained in the same file size, and that player incompatibility problem is a thing of the past. So for MP3, I now recommend turning ON VBR, and setting the VBR quality to "Highest."

But for AAC, if you turn on VBR, iTunes won't let you go higher than 256. So for AAC, I leave VBR off and crank it up to 320.

The choice of "Joint Stereo" (only an option for MP3) is a bit more controversial because some MP3 encoders use an inferior way to get "Joint Stereo". The negative effects can be a lessened stereo image, and audible artifacts. In theory, "Joint Stereo" is better because it frees up room for more audio in the same bitrate, by skipping redundancies. But in certain situations, it has sounded worse. This is one item to listen to and judge for yourself. If you are using the LAME encoder (see below), Joint Stereo should be on. With iTunes' built-in encoder, listen and decide for yourself.

Personally, I turn off "Filter Frequencies Below 10Hz" (also only a default option for MP3). True, the human ear can't hear frequencies that low. But any filter has the potential to introduce aliasing effects at other frequencies, in the audible range. I've not tested this, but based on my knowledge of DSP theory, I choose to turn off this filter.

OK, now that you've got those settings right, check out this article about getting all the track information right:
/forum/mp3-metadata-id3-tag-filename-best-practice

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If you'd like to take it a step further, there's a relatively easy way to get better quality than with the stock iTunes encoder. This method is for OS X. (I think there's a way to do this on Windows, too.)

The LAME open source MP3 encoder is agreed by many to be superior than the MP3 encoder used by iTunes. There is an OS X application called iTunes-LAME which allows you to get the better LAME encoding while still using the great iTunes interface for managing your music. It is a seperate application which can be invoked from with iTunes, and it contains within it the LAME encoder.

First, download iTunes-LAME here:
http://blacktree.com/projects/itunes-lame.html
or here:
http://code.google.com/p/blacktree-itunes-lame/downloads/list

Run the app. (In recent versions of Mac OS, it won't show up in the Scripts menu in iTunes. In older Mac OSes, it shows up there as "Import with LAME".)

To learn about picking your encoding setting, read this:
http://wiki.hydrogenaud.io/index.php?title=Recommended_LAME

I use this encoder setting, which creates the highest quality constant-bit-rate stereo 320k MP3 file with full ID3v2 tags:
--preset insane -q 0 --add-id3v2 -m s --verbose
...which is the same as this,
-b 320 -q 0 --add-id3v2 -m s --verbose

You could stop here, because that should be everything you need.

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BUT, if you want to take it another step further, note that the iTunes-LAME front end has stopped development, and there have been more recent versions of LAME since the one it includes, v 3.96.1.

To get a more recent version of LAME (as of 5/2011, 3.98.4 is the latest OS X compiled version I found) to use with iTunes-LAME, download it here:
http://www.rarewares.org/mp3-lame-bundle.php
If that link expires, check here:
http://wiki.hydrogenaud.io/index.php?title=LAME_Compiles

Then, replace the LAME in iTunes-LAME like this:
1) Quit iTunes-LAME.
2) Control-click iTunes-LAME and select "Show Package Contents".
3) Use the newly downloaded file "lame" to replace the older version in this folder: iTunes-LAME.app/Contents/Resources/

When you next launch iTunes-LAME, the "about iTunes-LAME" window might not show the new version, but it's there. Unfortunately iTunes' "Encoded with" field (get info, summary tab) doesn't show a dot release (only showing "3.98" rather than "3.98.4").

(Note that if you check the iTunes-LAME preference "Put LAME version in comment", it actually only puts your encoding options there, and only if there's not already a comment.)

And if you'd like to dig in to the source code of the LAME encoder (or recompile for your system), here are links to the uncompiled project info:
http://lame.sourceforge.net/
http://sourceforge.net/projects/lame/

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