[DC LoCo] /. News: Apple's Lossless Audio Codec (ALAC) Now Open Source

Kevin Cole dc.loco at gmail.com
Fri Oct 28 18:16:44 UTC 2011

And, to belabor the explanation a bit further via analogy rather than
total accuracy:

Let's say you have a phrase like "the lazy brown fox did not jump over
the lazy brown dog's back."  A lossless compression could analyze it
and note that "the", "lazy" and "brown" occur multiple times.  So it
recodes as something like "[1=the, 2=lazy, 3=brown]1 2 3 fox did not
jump over 1 2 3 dog's back."  The part in brackets [...] is the
encryption key or hash table, and the rest is the encrypted message,
or hashed message.

A lossy compression may determine that "the" is "mostly noise" in the
signal, and can be eliminated entirely or shortened to "a", or that
"did not" can be contracted to "didn't" without bothering to record
anywhere that these changes were made to the original.  In the case of
eliminating or replacing "the" with "a", the listener / reader may
very well notice the change.  On the other hand, hearing or reading
"didn't" in place of "did not" is less likely to be noticed by the
casual listener / reader.

A crude analogy, but hopefully illustrative.

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