The actual encoding process consists of the following steps:
* The signal is converted from time-domain to frequency-domain using
forward modified discrete cosine
<http://en.wikipedia.org/wiki/Modified_discrete_cosine_transform> transform
(MDCT). This is done by using filter banks that take an appropriate number
of time samples and convert them to frequency samples.
* The frequency domain signal is quantized based on a psychoacoustic
<http://en.wikipedia.org/wiki/Psychoacoustics> model and encoded.
* Internal error correction codes are added;
* The signal is stored or transmitted.
* In order to prevent corrupt samples, a modern implementation of the
Luhn mod N algorithm <http://en.wikipedia.org/wiki/Luhn_mod_N_algorithm> is
applied to each frame
With AAC encoding you can compress the 6 channels of CD quality 5.1 into
space of an uncompressed stereo stream. I found the term "psychoacoustic"
interesting because it is a concept I was unaware until I started the
research into compressing audio data. I hope this answers your question.
If not, rephrase the question and I will try to answer you question better.
Joel
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
------------------------------------------------------------------------
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/naturerecordists/
<*> Your email settings:
Digest Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/naturerecordists/join
(Yahoo! ID required)
<*> To change settings via email:
<*> To unsubscribe from this group, send an email to:
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
------------------------------------------------------------------------
|