[timmerk]

I've read that 128 AAC is better then 160 MP3, but is it even better then 192 MP3? What about 256 MP3 vs 128 AAC? I ask because I have duplicate songs, and am not sure which one I should delete.

(P.S. I know that it's a 128 KBPS bitrate MP3, and not just '128 MP3', etc.)

[Horsepoo!!!]

Well it depends...is cake better than pie?

[- - e r i k - -]

Can YOU tell the difference?

[timmerk]

No, I can't, but I wouldn't be able to sleep at night knowing I got rid of the better quality one.

[- - e r i k - -]

Get rid of the AAC then. 192Kbps MP3, especially encoded with LAME would be marginally better.

[peeb]

There are a lot of variables in the mix here - did you rip these from CD?

[timmerk]

The MP3s are from CDs and the AAC files are from the Apple Store.

[cgc]

Originally Posted by Horsepoo!!! 

Well it depends...is cake better than pie?

No. Mmmm...pie...*drool*

[King Bob On The Cob]

The MP3 should technically sound better if they came from the same source, but the iTMS rips from the master, so I don't know.

[Thinine]

Nah, the AAC will sound better in most cases. But really, I doubt you'd be able to tell the difference.

[peeb]

Why do you say the AAC will sound better in both cases?

[Aegis]

Yeah there's lots of factors here. Your ears. Your equipment. The encoder for the mp3 (iTunes isn't the best at mp3 encoding). The type of music.

I would guess that 160 AAC / 192 mp3 is probably the cutoff where most people can't distinguish it from a higher bitrate. If it were me personally I'd keep 192+ mp3's over 128 AAC.

[SpaceMonkey]

Originally Posted by Aegis 

Yeah there's lots of factors here. Your ears. Your equipment. The encoder for the mp3 (iTunes isn't the best at mp3 encoding). The type of music.

I would guess that 160 AAC / 192 mp3 is probably the cutoff where most people can't distinguish it from a higher bitrate.

Bingo.

Both AAC and MP3 are very broad definitions that basically describe the output side: how the software decodes the file to play the music. The process of creating that AAC or MP3 file can vary depending on the encoder used. MP3 is an older file format, and there are a lot of different encoders that have been developed for it. AAC is newer, and there haven't been as many encoders developed for it.

Among MP3 encoders, iTunes is considered to be not very good. A better MP3 encoder is the open-source project called "LAME," which is available on the Mac as a Unix executable and as part of a couple of different software packages. One of the more popular is called Max, which is a CD ripper and encoding tool.

Among AAC encoders, iTunes is considered to be very good.

Public listening tests indicate that the latest versions of LAME MP3 are indistinguishable from iTunes AAC files at ~128 kbps variable bit rate (VBR). So 128 kbps LAME MP3 = 128 kbps AAC.

[davedecay]

I love iTunes LAME.
iTunes-LAME Encoder 2.0.9b4 - MacUpdate

I'd guess a 192 kbps MP3 might sound better than a 128 kbps AAC, but it might also depend on the type of music and complexity.
Compare classical, newer rock, classic rock, or whatever you prefer. Newer CDs (and presumably AACs) are mastered differently from older, pre-CD music. They are, by and large, LOUDER, and use far more compression and expansion filters. This can have an effect on how MP3s/AACs sound when encoded from newer CDs. My guess is labels don't want people doing it, so they try to make compressed formats sound worse, which in turn encourages people to buy the CD instead of the lower-quality files.

If you really want to dig in, read some of the discussions on this board also:
Hydrogenaudio Forums -> MP3

Another informative link about compression & lossy formats:
The AudioFile: Understanding MP3 compression: Page 1

[peeb]

Originally Posted by davedecay 

My guess is labels don't want people doing it, so they try to make compressed formats sound worse, which in turn encourages people to buy the CD instead of the lower-quality files.

I have a hard time thinking there is a real conspiracy of this level.