Hi there,
The actual specifications are copyrighted, and you are unlikely to
find them for free online. Furthermore, they sound very complicated!
"This is a lossy compression, which means, you will certainly loose
some audio information when you use this compression methods. But,
this lost can hardly be noticed because the compression method tries
to control it. By using several quite complicate and demanding
mathematical algorithms it will only loose those parts of sound that
are hard to be heard even in the original form. This leaves more space
for information that is important."
http://www.dv.co.yu/mpgscript/mpeghdr.htm
The techniques used in MP3 compression include:
The masking effect
------------------
When two sounds play at once, and one is much louder than the other,
it's okay to get rid of the softer sound, because we couldn't hear it
anyway.
The minimal audition threshold
------------------------------
Sounds the average human cannot hear, are not required.
The joint stereo
----------------
Often much of the same information is duplicated between the right and
left channels. This information only needs to be there once.
There's also the reservoir of bytes, and the Huffman coding, which are
a bit more complicated. Plus, the level of compression you choose
affects the quality.
I've found three sites for you which explain how it all works, from
simplistic to technical.
MP3 Club Pro
http://www.mp3clubpro.com/english/techniques_en.html#signet4
(nice balance, translated from German)
Fraunhofer IIS
http://www.iis.fraunhofer.de/amm/techinf/layer3/
(quite technical)
R3 Mix (click on "quality" in the left menu)
http://www.r3mix.net/
(technical)
Search strategy: Searched for MP3 in Google Directory
Best wishes,
robertskelton-ga |
