Some days ago I registered at www.itunes.at (iTunes Austria) to download music
from Apple's great iTunes music store.
At first everything looks really good and fine... the design of the shop, the iTunes
software and everything round it/them is amazin... typically for MAC.
But when I bought my first song form the music service (3 Doors Down -
Kryptonite *g*) I realized that the quality of the file is only about 128 Kilobits (!?)
I was really angry because I thougt that Apple represents "high quality" so that
everything from this company really is "really high quality". The 128 Kilobits are
not bad but they are not really high fidelity...
Because of my little problem with iTunes I searched through the internet and
asked some smart people about the issue... and I found a pleasent solution:
The files offered at iTunes are not MP3 encoded. They have got a special standard
called MPEG-4 AAC (Advanced Audio Coding).
The difference between MP3 and AAC is that a file encoded with AAC at 128
Kilobits is equal to a file encoded with MP3 at 160 to 192 Kilobits (depends on
the song, etc. )
So the AAC standard is cleverer than the MP3... same size, better quality.
An short excerpt of the AAC wikipedia article explains the differences
( Source: http://en.wikipedia.org/wiki/Advanced_audio_coding )
AAC's improvements over MP3
Some of its advances:
Sample frequencies from 8 Hz to 96 kHz (official MP3: 16 Hz to 48 kHz)
Up to 48 channels
Higher efficiency and simpler filterbank (hybrid → pure MDCT)
Higher coding efficiency for stationary signals (blocksize: 576 → 1024 samples)
Higher coding efficiency for transient signals (blocksize: 192 → 128 samples)
Much better handling of frequencies above 16 kHz
More flexible joint stereo (separate for every scale band)
What this all means to the listener is better and more stable quality than MP3 at
equivalent or slightly lower bitrates.
I hope that I could bring some light into this iTunes secret :-) so that no one
will wonder anymore about the 128 Kilbits in his/her music.
For more information about the differences of the music standards or some
other information visit the following websites:
http://www.apple.com/support/itunes/musicstore/songs/
(Official Apple Support Site)
http://en.wikipedia.org/wiki/Advanced_audio_coding
(Wikipedia Information Site)
Greetings & Have fun with your great iTunes music @ high quality :-)
Harry1984a


