Axiom Home Page Forums General Discussion Technical Questions sittin here listening to my Ipod

Does anyone now what kind of sound loss you get from compressed audio files like AAC or MP3?
I've docked my Ipod to my stereo and it sounds good but I was wondering in what areas you get sound loss.
Ken, thought you might have an answer being a Mac IT guy.
Gotta love Macs!!!!
Bray

MP3 and AAC are designed to keep lots on information in areas we hear best (midrange) and lose information in areas that we humans generally aren't attuned to as much - lower end bass and the high-end of the spectrum.

The more compressed, the smaller that "sweet spot" of good sounding stuff gets. The human voice can be really, really compressed with pretty good sound quality. The more dynamic the source, the less compressed it needs to be to still sound "good."

Most of the time you can notice an MP3 or AAC by muddy bass and "swishy" sounding high-end stuff. Cymbals especially seem to suffer.

It's all a lot more complicated than that, but there it is in a nutshell. I usually stick to AAC at 192 or better, and that seems to be the best compromise between size and sound quality, or at least to my ears. I still use MP3 as well sometimes if I know it's not going to be played on a mac or ipod - again, I just use 192bps.

Thanks! That answers my question perfectly.
Bray

First of all, it depends on the encoder. There are many different MP3 and AAC encoders. The best of the AAC ones are iTunes, and the best of MP3 would be LAME encoders when using the --alt-presets(hydrogenaudio.org is your friend). VBR is a nice method of encoding.

In my experience, you don't really notice a difference with the higher bitrate stuff unless you listen to the lossy for a long time then hear the lossless. I tried this in a blind test, but it's really not much.

And, you'll notice it in the cymbals first and foremost. Don't bother listening for the rest if that song has cymbals - because if some other part of the music is screwed up a tiny bit with the lossy compression, the cymbals will probab ly be totally massacred anyway.

I use Itunes importing at 128kbps. That is the highest setting available. Is that lossless?
I bought the 40 GB model Ipod. So far I've got just over 3000 songs on it, and still have about 50 CDs worth of songs in my collection to download. Whats I really like about it is that I use it as an external hard drive to download images onto (I'm a photographer) which makes the whole thing a tax write off. It seems to be more stable than a maxtor or lacie external hard drive.

What version of iTunes are you running? If you're importing AAC, you can acutually choose Custom and go all the way up to 320kbps. 128 is not lossless. If you get the latest version of iTunes (4.6), you can import lossless (according to Apple) and with 2:1 compression. Nice iPod, btw...

I'm running OS10.2.8 and I dont think I can get the newest Itunes without OS??? Panther. Is that correct?? Really dont want Panther now because I heard that Cheetah will be out soon.

Actually, Tiger is the one that will be out, well, not soon, but before the end of the year. I believe iTunes 4.6 is available for 10.2.8, though. Check Software Update. In any case, I'm pretty sure that you can set custom AAC bitrates up to 320kbps in iTunes 4.0 and up.

Hi Bray, Thasp, all,

Some years ago, I was part of a listening panel doing double-blind tests of compression algorithms to be used for professional digital broadcasting and music distribution (including some from Dolby Labs). These tests were also duplicated by panels in the U.K and in Australia.

If the data rate was high enough--320 kbps--there was little or no difference in the various compression schemes. As the data rates went down, percussion instruments often showed up flaws. Castinets were really critical and cymbals as well. Also the sibilants on unaccompanied vocals would cause problems.

Pop/rock music generally wasn't as critical as classical works, but the sibilance flaws showed up on some vocals.
With the higher data rates, the compression schemes were essentially transparent. I've done comparisons of Dolby Digital 5.1 (a lossy compression scheme) with master mixes (no compression) and DD5.1 is essentially transparent.

Regards,

Thanks Ken, Thasp and Alan! You guys are a gold mine of info!
I had just done an update on my mac about a month ago, and was
updated to itunes 4.5 not 4.6. Since ,I have updated to 4.6,and found the custom settings to import lossless files. Does this mean I"m going to have to re-import my entire cd collection?
I'm afraid it does!! Crap!!
I think I probably have 48 hours in just importing what I've done so far.
Does it take longer and take up more hard drive space to import these lossless files?
Thanks again
Bray