Sound quality penalty with AAC 256 VBR vs. Apple Lossless
Reply #6 – 2007-09-17 15:31:07
1. What are the audible artifacts of lossy compression when using higher bit rates like 256? 2. I’ve heard that AAC is superior to MP3 at lower bitrates, but what about higher ones like 256 or 320? 3. What differences would I be able to hear between files encoded at AAC 256 VBR, vs. Apple Lossless if using a decent set of earphones? (I’m currently planning to get a pair of Shure SE210s with the iPod). The previous answers are technically correct - we don't have your ears - but we can reflect the combined experiences of many people and many listening tests as follows. 1. Unless you have a really bad encoder, artifacts are few and far between at 256 kbps. There are killer samples, but most of the time most people won't hear any difference from the lossless original (i.e. it is transparent) under proper blind test (ABX or ABC/HR) conditions. For a highly-rated encoder like iTunes or Nero for AAC-LC or LAME for MP3, you'll be fine for the vast, vast majority of your music. 2. From around 128kbps, the LAME v3.97 (-V5 --vbr-new) MP3 is almost as good as iTunes AAC, and both are widely considered to be mostly transparent or most differences that can be perceived are not annoying. For most people LAME -V3 --vbr-new (~160 bps) is pretty robustly transparent and LAME -V2 --vbr-new (190-200kbps) is very robustly transparent. For compatibility (e.g. if you get a car stereo that supports MP3 but not AAC) you might consider using MP3 as it remains by far the most widely supported lossy compression format. If you're sensitive to pre-echo, you might find that AAC's improved time resolution is an advantage over MP3 at any bitrate. You're very unlikely to hear much difference between any of the good encoders once you are above about 160-170 kbps in VBR mode, and there's little to be gained as you go even higher (e.g. 256 or 320 kbps). 3. You're very unlikely to be able to tell the difference between any good lossy encoder (including iTunes) at 256 kbps and the lossless original for the vast majority of music regardless of your earphones. For that matter, 160 kbps or 192 kbps is already at that point. With loudspeakers, it's even harder to tell the difference than with earphones/headphones.