iTunes or CD quality- just not sounding that good anymore?

I've noticed a quality diff. on music that has been ripped from a CD. It is most noticeable on a good stereo. Make sure to adjust the settings so the quality is the best. The compression will be lower and the file size will be higher.

 

iTunes and ripped CD's usually end up as MP3, WMA, or other compressed audio files. For comparison, a normal CD delivers 1.4 MBits per second of data when playing audio. The typical MP3/WMA is encoded at 128 to 192 Kbits per second. This is 1/12th to 1/8th of the data rate, due to compression. Guess what, you don't get something for nothing; that compression technology is LOSSY. MP3/WMA files are only as good as CD's on a crappy system (portable player, earbuds) in a crappy environment (car, subway, office, sidewalk, etc). They won't stand up to a decent stereo in a quiet room environment.

If you want good music, always keep a CD quality copy and encode separately to MP3/WMA music folders just for portable use.

 

1.4MBit/s?

Wow, that's alot more than I thought. So even 320Kbit/s files are a long way short of CDs... You always see 320Kbit/s being toted as "CD Quality".

 

iTunes sound is unlistenable. I don't know how they get away with it. ...wait, yes I do.

 

1.4Mb/s is the raw digitized audio data rate, which is what CD's used before compression technology became cheap. When set to light compression 2:1, the losses/errors are generally undetectable. As you crank up the compression ratio, 3:1, 4:1 (where 320 Kb/s is) then it is just detectable if you are critical and listening carefully. Crank it up even further 8:1, 12:1 or higher, and it becomes progressively more noticeable, until it becomes atrocious.

 

You can also transfer your CDs to AIFF rather than MP3. Much better quality (1.4MBit/sec), and still plays on iPods. You can't get it on iTunes, though.
The big deal of all this is that you need a decent audio system to notice the difference. If you stick to crap computer speakers, you won't notice a thing.

 

Think of converting to MP3 like cutting the top and bottom off of the audio. Your only left with the middle. No real highs, no real lows. That's why they are so small.

 

Not really true.

MP3's and other audio compression methods work on a variety of principles, but they generally have full-range or almost full range frequency bandwidth (though you can set MP3 encoders to be narrower bandwidth if you want even more compression).

One of the methods used is psycho-acoustic perceptual coding. What that means is that the encoder eliminates relatively weaker lower frequency signals, below a certain amplitude threshold, when there is a strong high frequency signal present. This is because your ear doesn't really "hear" those lower frequency signals in that situation so the encoder saves the data costs of transmitting what it thinks you can't "hear".

Another method is to encode low frequency signals as mono rather than stereo. Your ear can't stereo-locate lower frequencies, so that data is combined to save bits again. This low frequency stereo-location limitation is why subwoofers are single speaker, even in a multi-channel audio system.

A third method is just based on the amount of signal information present at the time. If the signal is fairly simple, then the compressed data rate is naturally low and it gets encoded faithfully. If the signal is fairly complex (lots of frequencies, high dynamic range, lots of transients), then the encoder will lose some of the information in order to limit the bitrate; so crescendo's, as an example, won't sound right.

 

What about --ape/--aps mp3s? If you burn those how is the quality?

 

APE and APS are settings for the LAME encoder. They are presets that the LAME developers have optimized to give better encoding performance than the first generation MP3 encoders. One enhancement in these modes is that they have VBR (variable bit rate) capability turned on, meaning they can allocate more bits to more complex portions of the music and less to simpler portions, so the bitrate averages out to a lower level. Net result is that they are higher quality for a given bitrate than a "standard" MP3. But they are still lossy.

 

If your ripping something in itunes you plan on putting on a cd just go into the settings and switch it to wav format. Then burn the wav files. MP3 sourced cd's certainly won't sound great on a high end system. But by ripping it to wav files your aren't compressing it.