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Posted by Richard Crowley on 11/29/07 23:41
"Eeyore" wrote ...
> There is a BIG difference however. A true CODEC operates
> in real time. Zipping and unzipping files is however not a real
> time process.
>
> Wikipedia also takes the view that codecs must be real time.
> http://en.wikipedia.org/wiki/Codec
> "A codec is a device or program capable of performing encoding
> and decoding on a digital data stream or signal. "
Sorry, I can't see the words "real time" anywhere in your quote
(or on the whole page, for that matter). Can you help us find them?
Furthermore, it can be BOTH. You can take WAV files and
encode them into FLAC (as a batch process, likely very-much
faster than "real-time"), and then take the FLAC file and decode
them *in real-time* when you want to listen to them.
> Note 'data stream' or 'signal'. NOT file.
Nothing operates on "files" as such. Anything you do with
a file turns it into a "data stream" from the CPU's POV.
You cannot read a "file" without turning it into a datastream
nor can you write a "file" without it exsiting as a datastream
on the way from the HD controller to the drive. (And indeed,
as the HD head reads or writes the "file".)
Furthermore, we have a problem with defining "real time".
When we talk on a cellphone, we are (mostly) unconsious
of the fact that it isn't really "real-time" due to the nature of
the time-domain sharing of the cellsite with hundreds of
phones. It is very fast, but not technically "real-time" in the
strictest sense. You can demonstrate the effect by calling
someone standing next to you and noting the difference
between through-the-air real-time vs. the encoding, trans-
mission, and decoding through the cell phones.
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