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Greetings Frank, how are you and yours?
I was wondering if you knew a bit about mp3 conversion algorithms used. It
seems to me that it would have to be a Fourier transform of the sampled waveform
to encode then reverse the process to decode for 'playback'. I'm not having much
luck finding the more technical details of the process. When I do a search I get
thousands++ of hits for conversion software ect. and little in the way of technical
stuff.
To save you a bit of time - I understand electronics, ie AD 'conversion' via
sampling the input signal, the 'ins and outs' of sample rates, 8-12-16 bit
AtoD etc. Also I have a fair bit of math (third year eng. level) and understand
Fourier transform functions [-- Fourier (fo rya; E fore er)
1 Francois Marie Charles (fran swa ma re sarl)
1772-1837; Fr. socialist & reformer
2 Baron Jean Baptiste Joseph (zan ba test zo zef)
1768-1830; Fr. mathematician & physicist
(C)1995 Zane Publishing, Inc. (C)1994, 1991, 1988 Simon & Schuster, Inc.]
I am particularily interested in "lossless" encoding as there is no way
that I am aware of to do that kind of encoding without losing something. The
only thing that approximates the analog signal is a wave file (in my mind).
Correct me where I go wrong (you reminded me of RIAA bandpass filters - oops):
We 'sample' the analog signal and use an AD converter to develop a binary file
called a 'wave' file with sample rate being important as the higher the sample
rate (frequency) the better the binary represents the original analog signal.
We then use an alogrithm to 'sample' the wave file and develop a 'compressed'
file for easier transmission and storage, reversing the process when the
'compressed' file is 'played back' where another algorithm 'rebiulds' an
APPROXIMATION of the original wave file which results in loss of frequency
response - the lower the 'bit rate' the higher the 'amount' lost.
All of this results in a 'loss' of frequency response, and if I remember
correctly our frequency range of hearing is 100 to 20 kHz. Above and below
our range of hearing we 'feel' the frequency rather that hear it.
Also - most modern electronics (for the last 50+ years) is designed to provide
a 'bandwith' well above and below human hearing frequencies. This most particularily
applies to 'storage' media - ie: vinyl records, tape Cds and whatever.
I ramble, do you have any info??
PS - I have been 'out of school' for nearly 40 years so am not 'up to date'
on some of the stuff used in the digital world.
--
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