Converting aac (m4a) to mp3

cfleck

cfleck

tired
I searched around for this but couldn't find anything. Forgive me if this has been addressed.

I'm considering converting my audio files to mp3. Currently the bulk are in aac (m4a) format. If I set the import setting on iTunes to mp3, I can just ctrl-click the songs I want and select "Convert Selection to MP3". Easy enough.

My question is, how much quality am I losing when I do this? I'd rather not have to re-rip my cds, but if the quality loss it significant I will.

Yes I know that I could just convert, listen, and make the call. I'm just a bit curious about the details.
 
Well in principle...

When you re-rip music you are taking a downgraded abstraction of a downgraded abstraction, so you will inevitably lose a bunch of quality, else you could improve your collection by converting everything to a higher bitrate.

It'll come down to whether the quality makes a difference to you, which will likely depend on how you listen to it. On a big stereo you'll notice the difference, you may not on a walkman or maybe an iPod (though with headphones like the apple earbuds the sound reproduction is pretty good).

Why are you considering mp3? It might make a difference. Also, if you decide to do the conversion, make sure you back up the aac files first, otherwise there'll be no going back.
 
I'm considering mp3 because I'm also considering an audio player that isn't an ipod. In my shopping I've found that a lot do not support aac. That led to a whole other train of thought that has me thinking about mp3 being the only player that has shown staying power.

So really it is a matter of it working everywhere for a long time.
 
Quality is very subjective, so it's impossible to say "how much" quality you'd be losing. Encoding to mp3 from AAC is just like encoding from a CD, only you're starting with a lower-quality source. So it'll be a close approximation of a close approximation of the CD.

What's the bitrate of your AAC collection? The higher the quality of the source, the less you'll notice the difference. I would personally not want to convert 128kbps AAC to mp3, because I think that quality level is just too low to remain "listenable" after further degradation. If it were 320kbps, though, I'd go ahead and I'd probably never notice the difference.

It also depends a lot on the kind of music you have. Anything with powerful drums, for example, will compress especially badly, and the quality loss will really be exacerbated by re-encoding. I've heard 128kbps mp3s that were re-encoded from WMA, and they were barely listenable because of how butchered the sound of the drums was. It wasn't so much a "beat" as it was rhythmic static! Violin music, on the other hand, compresses pretty well (at least to my ears).

That's really all I can say on the matter. My final advice: convert, listen, and make the call, just like you said. :)
 
I like the MP3 format because many in-car CD players support MP3 CD's (around 110 songs per disc) but not AAC CD's. Great for rental cars.
 
There are great variations in the quality you can achieve during an MP3 conversion. As everyone's said, the better source material the better end product, but the converter itself is also important.

I use the LAME encoder for all MP3 ripping, as it's been updated and tweaked since 1999 by crazy audiophile computer geeks. You can encode absolutely perfect MP3s in a straightforward fashion, and there's a nice standalone encoder you can call via an AppleScript command to encode whatever list you're looking at in iTunes.
 
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