I've been ripping my CD's to MP3 using LAME, with -preset fast standar (or -V 2), since audio listening tests find that LAME with these settings is transparent and as good as top quality Ogg Vorbis or AAC, and MP3 is still a bit more supported than AAC.
Lately, I've been running out of space on my iPhone and I'm considering to start using AAC to compress my music, but there is no point using iTunes+ (AAC at 256 kbps) or AAC at 192 kbps since that would still occupy the same space. It should be AAC at 160 kbps or 128 kbps, I guess.
iTunes has an option to convert all my music to AAC 128 kbps when synchronizing the iPhone. Is 128 kbps AAC equivalent to the LAME encoding I've been using? If so, I could use that option, while I re-rip my collection to AAC 128 kbps.
What else would you recommend?
Best Answer
There's a few major variables at play here.
First of all, you have to determine the suitability of 128 Kb/s AAC for your listening. This isn't just about transparency though, but your listening environment. Chances are, the kind of places that you'll be playing music from your phone aren't rigorous enough listening environments that any encoding artifacts would be noticeable, much less bothersome.
Second, if you're talking about transcoding your MP3s to AAC when you sync to your phone, there's going to be some additional quality loss beyond a normal encode from the source CD. You'll have to listen for yourself to determine whether or not that's a problem for you. Considering the high quality of your MP3s, the resulting AACs should sound nearly as good as an encode from CD.
Finally, there's the whole question of bitrates and transparency. For a very large subset of the population, 128 Kb/s MP3 and AAC are both transparent without training or practice listening for artifacts. Unless you do critical listening like participating in listening tests, chances are that 128 Kb/s (or LAME @ -V 5) would be just fine.
Just as an anecdote, even though I've spend quite a bit of time personally listening for encoding artifacts and killer samples, 64 Kb/s AAC+ is good enough for me to listen to at work.