Perhaps this post belongs in a portable audio forum.....it does relate to AAC however.

Given the following condions: 1) 3G iPod or iPod Mini, and 2) Shure E2c Earphones, is there a noticable difference in the sound quality between an iTunes encoded song at 128 and 192??? (of course it varies from song to song, assume rock in the style of Pearl Jam or Oasis for comparison)

I ask because I cannot notice a difference between 128 and 192 using my Sennheiser MX400s with my iPod, but will soon be upgrading to Shure E2cs and want to compress my songs in the best format. I have been using 128 because I can hear no advantage of 192 with my current headphones.

Users with high end phones are encouraged to respond.

Well, I'd recommend to get those headphones and then try if you can hear a difference.
This way you make shure you have exact results.

Or is time short so that you have to compress your music NOW?

Use ALAS ;-)

A better test is to differentiate between 128 and 192-encoded files on your computer or decent piece of sound equipment.
Even if you can tell the difference, you still probably won't notice it on the iPod.
The iPod isn't my choice for sound quality, just convenience.

Eh? Perhaps you mean ALE (Apple Lossless Encoder)?

Keep in mind that sound quality is pretty compromised in a portable environment, regardless of what bitrate you choose. The Shures will block a lot of sound, but there will still be some ambient noise.

For me, space is a much more important consideration. For my recent rips, I've been using ALE for the computer and AAC at 96 kbps for the iPod. Perhaps if I had done that from the start, all my music would fit on my iPod.

I've found this to be rather true myself. Actually, I did a little double-blind test of my own a few weeks ago with my iPod....I encoded some AAC samples at 128, 192, and 256kbps, randomly renamed them in the terminal without knowing which was which, and then played them, in shuffle mode, as a playlist. I then listened to the shuffled files with my SportaPros and recorded my impressions. Result: I couldn't tell the files apart enough times for it to be statistically significant (it was close to chance, actually ). On the computer, though, I can reliably ABX up to 192kbps AAC for some material. Thus, I've concluded that for the iPod, 128kbps is enough because the sound quality doesn't improve much thereafter; for the computer, it's definitely not enough. YMMV.

I use Etys (usually w/Meta amp) with my iPod, which are more revealing than the Shures, but I'd be surprised if most couldn't hear the difference between 128 and 192 AAC with decent equipment (the part rarely discussed around here). Everyones ears are different, as are everyones portable environments (at least in my case less compromised than many think when "portable" comes up), so like as been said, try for yourself. My default is 224 for the road (and trying ALAC [ALE is just the encoder, right?] for home with better equipment), but I usually can't tell the difference between 192 and 224, except for some acoustic stuff in relative quiet environments (this is more common with the ER4P/S). My trials have been limited though. I say use 192 and forget about it.

I don't own an iPod but I do use Etymotic ER-4S cans - Mac to USB DAC to hi-fi. All of my personal listening tests (and I emphasize PERSONAL here - use what works for you and your equipment) found 128 kbps AAC to be inferior. On my equipment I could reliably identify the 128 AAC's 80% of the time. 192 is usually transparent, although I did find a few things that were problematic. My solution, then, is to encode everything at 224, even though I'm certain 192 would be sufficient for most things. I have the HD space to do that and the extra cushion of 224 kbps provides peace of mind. This is what works for me, but, again, depending on your hearing and equipment used, your mileage may vary.

I don't know where this started, but the Apple Lossless codec is called ALAC (Apple Lossless Audio Codec).

Propably my fault.
I don't know about Shure headphones but when I last time tried to abx Apple-aac @ 128 it was a miserable failure. If you are uncertain, go with 160 kbps.

Some very good replies. Thanks.





That's what I was afraid of, when I upgrade to Shure phones, I will be able to tell a difference (like I can when burning an audio CD from 128 and 192 files and listening to it on my higher end home stereo).

I wonder why the Apple store does not offer AAC in 192 if this is the case? Probably has to do with so many still on dial-up.

Probably has more to do with the fact that for most people 128 kbps is enough of a bit rate to satisfy them. Even with MP3. When using MP3 I use alt-preset standard. When using AAC I have found that using iTunes's encoder at 128 kbps satisfies me as well and I'm pretty good at picking out encoding artifacts. I have only been able to successfully ABX a few songs on decent equipment and those songs had cymbals alone without any other instruments playing. But still the songs I could ABX didn't sound bad. It's personal preference again. I'm sure that Apple thought a while about what bit rate to use for their store and probably found the best quality to size ratio with 128 kbps on most music. I've heard of other online music stores such as Real's Rhapsody using 192 kbps AAC but this wasn't because Apple's 128 kbps weren't good but rather a marketing move to attract people away from iTunes.

It started at Apple. They refer to it as "Apple Lossless encoder" on their website, in iTunes documentation, and within iTunes itself. Never have I seen a reference to either "ALAC" or "Apple Lossless Audio Codec" from Apple.

Encoded files say ALAC.

You guys worry too much about semantics.

If you don't mind the risk of an occasional artifact, you'll probably get more play time out of your battery with 128kpbs files. Just another thing to consider.

Personally I was not satisfied with iTunes AAC 128 on my iPod. That was quite a disappointment, MP3 at 160 or 192 seemed to sound more lively!

Note that this is all subjective feelings, I did not conduce a ABX test to confirm that. But I am very happy with iTunes AAC 160 for portable use.

I think I'm going to go with 192 from here foreward. Howver, I have about 500 files on my PC now at 128 and I do not see me re-compressing those for a long time.

Priority now is:
Newly purchased music at AAC 192
Re-compress 1000 files still in WMA at AAC 192
Re-compress 3000 files in MP3 160 (before I discovered APS) at AAC 192
Re-compress 5000 files in MP3 APS at AAC 192
Re-compress 500 files in AAC 128 to AAC 192

All the while, everything first gets an Apple Lossless copy from the CD. I then compress from Apple Losselss (whick keeps the tag info!!!!) It will be a long time before I get everything at AAC 192.

DO NOT TRANSCODE, THIS WILL MAKE QUALITY WORSE. And for the MP3´s and AAC´s it is not necessary because the ipod can play both.

Just leave your files as they are!

The only transcoding will be done from Apple Lossless. All files are first ripped to WAV with EAC and then converted to AL in iTunes.

He doesn't want you to hurt good music