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Old 03-28-2007, 10:25 PM   #31
EAGLE EYE
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Quote:
Originally Posted by Infinity tha God View Post
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something i learned in school that i thought was interesting.

mp3 audio
mpeg layer 3
motion picture experts group

cd quality- 44.1kHz, 16 bit resolution

a 2 track, stereo interleaved file
x
44.1kHz (or 44100 samples per second)
x
16 bits
___________
1411200 (samples per bit)

itunes offers their mp3's at a rate of 128kbps.

divide the number above by 128kbps ( 128000 bits per second) and you get 11.025. so the mp3 is compressed at a ratio of about 11:1.
for every 11 bits of dynamic range, you are getting 1 bit back.

now do the opposite and divide 128000 by 1411200.
0.0907029.......
converting that into a percentage, we get about 9%. this is how much is left of the original audio at 128kbps.
so 91% of the audio signal has been removed from the original waveform.
the data is removed permanently, based on priority.
low priority to keep masked frequencies, and frequencies outside of 20Hz-20kHz (the range of human hearing).
highest priority to keep are frequencies from 1kHz- 4kHz (mid range).

Ive been aware of most of this ^ for some time now. Also with all the money apple is raking in from selling songs through iTunes for $0.99 they should of been using the .flac file format since day one, when they launched the iTunes store.

Heres a brief description of what .flac files are:


Free Lossless Audio Codec (FLAC) is a popular file format for audio data compression. Being a lossless compression format, FLAC does not remove information from the audio stream, as do lossy compression formats such as MP3 and AAC.

Like other methods of compression, FLAC's main advantage is the reduction of bandwidth and/or storage requirements, but without sacrificing the integrity of the audio source. For example, a digital recording (such as a CD) encoded to FLAC maintains the quality of the audio perfectly. Audio sources encoded to FLAC are typically reduced in size 40 to 50 percent. FLAC is suitable for everyday playback and audio archival, with support for tagging, cover art and fast seeking. FLAC's open source royalty-free nature makes it well-supported by many software applications. FLAC playback support in portable audio devices and dedicated audio systems is growing.[1] Josh Coalson is the primary author of FLAC.
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