AAC vs. MP3 LAME vs. Uncompressed (long post)

[LagunaSol]

Carrying over a topic from the old forums....

I've been doing some head to head testing of some compression formats in trying to decide whether to re-encode all my CDs to AAC. To recap, I originally ripped all my CDs using MP3 192 VBR in iTunes, using the default encoder. I eventually came to the conclusion that they sounded like, uh, crap. So I did some research and decided to re-rip everything using LAME alt-preset-extreme, which I believe is 320 VBR (or so). The results were much, much more satisfying, despite the horrendously slow encoding times and large file sizes.

Now along comes AAC, and even though I have a 30G iPod, the more songs I can stuff on it while retaining great sound quality, the better. So I've been doing some critical listening using, admittedly, mediocre equipment (Sony MDR-CD780 headphones, about $150).

I ripped Bruce Springsteen's The Rising using various formats (with a sample file size of one song (Into the Fire) for reference):

AIFF (uncompressed, same as WAV for you Windows users) (51.2 MB)
MP3 LAME alt-preset-extreme (8.6 MB)
AAC 192 (7 MB)
AAC 160 (5.8 MB)
AAC 128 (4.7 MB)

I already know I'm not happy with standard iTunes MP3 192 encoding, and wouldn't even give standard MP3 128 (shudder) a chance.

Files were opened in QuickTime and played simultaneously, blindly toggling between versions.

My conclusions (and I hope others do some similar testing to confirm or dispute my findings/opinions):

AAC 128 vs. AIFF (uncompressed)
I could differentiate between AAC 128 and uncompressed AIFF fairly reliably. It was very close, but the vocals were a touch muddier and more fatiguing in the AAC version. I would expect this (it is a compressed file after all).

AAC 128 vs. MP3 LAME extreme
I could not reliably differentiate between the two. This is a good thing, as I know I can now double my song storage space with comparable quality. Goodbye MP3 LAME, hello AAC!

AAC 192 vs. AIFF (uncompressed)
I could not reliably differentiate between the two. The AAC 192 vocals are brighter and cleaner than the AAC 128, and close enough to AIFF that I couldn't tell them apart.

AAC 160 vs. AIFF (uncompressed)
Again, I could not reliably differentiate between the two. This is very good; I know I can drop down to 160 kbps and keep pretty darn good quality. There may be a slight difference in quality, but not enough that I could perceive it or be bothered by it.

I also took my iPod into a local electronics store that carries some high-end equipment. I patched into a $5,000 Denon receiver and a set of $1,500 Energy speakers (not fanatical audiophile quality I'm sure, but better than anything I'll ever own, at least on the receiver side). This test was not effective for me: I couldn't switch between song versions on the fly. I'd have to stop the song, scroll to the next version, hit play, and start the song from the beginning (or try to scrub to the same spot I left off). This didn't work for me at all. All versions sounded pretty good, even the AAC 128.

Bottom line? AAC is the Next Great Thing. I'll have no problems paying .99 for songs online at the 128 rate. Sure, I'd prefer 160 at least, but that's fine. 128 sounds pretty darn fine, especially at 1/10 the file size of the uncompressed original.

Now my dilemma; do I re-rip everything using AAC 128, 160, or 192? I'm certainly going to AAC, that's for sure. AAC 160 seems like the safest choice for me for good quality and good file size. Sounds as good (to me) as LAME extreme, at 1/3 smaller file size.

Any contrasting opinions?

[LagunaSol]

I finally found a couple more resources on this topic:

http://www.macintouch.com/itunes15.html#may09

http://www.recordstorereview.com/misc/aacmp3.shtml

I was surprised by Gunnar's findings (second link). He certainly appears to know far more about this type of testing than I do, has better equipment, and knows what to listen to when comparing the different encoding schemes. I'm not able to describe the differences I hear as he can. But to me, standard MP3 encoding in iTunes has noticeably *bad* results. To me, AAC at 128 sounds better than standard iTunes MP3 192, and I have a hard time telling the difference between AAC 128 and LAME alt-preset-extreme (approx. 320 VBR).

His music selection of course makes a difference, and he may listen more critically than I do, but my threshold for "quality" sound seems to lie at the AAC 160 or 192 level. Perhaps I need to test on a good stereo system. Maybe this is how I can justify such a purchase to the wife. :p

I have similar findings. Using AAC, my ears stop working around 160bit. I can not tell the difference between 160 and 320 AAC. I can tell the difference between LAME standard and AAC 160. I can not tell the difference between LAME extreme and AAC 160. I encode at AAC 192 just in case I come accross a hard to encode track.

[eustacescrubb]

I have the same track he used ("I Surrender Dear"), so I'll have to keep what he wrote in mind when I get to the "K"s in my re-encoding project. For now, I use 160k AACs.

[Ignodium]

So is 192kbps AAC really worse than 160kbps? I want to re-encode into AAC soon, so it matters to me which is better.