* "Remko van der Vossen" <[EMAIL PROTECTED]> on Mon, 01 May 2000
| You stripped away my and someone elses original point, modern dat
| compression is strictly in the digital sense of the word,
Because you and "someone else" ignored my point that CD-DA sampling is a
form of *ANALOG* data compression.
| Analog data has no specific size, yes on a 60 min tape exactly 60 mins of
| audio wil go on, but if you speed up the tape less will go on,
Which is not really all that relevant to CLV Laserdisc, which is
fundamentally identical to CLV Compact Disc, which is the original
comparison that I made. The differences are in media size and composition,
not effective data density.
| But that is compression too... in a matter of fact someones original
| statement is true, anything you'll do to make it smaller is a form of
| compression as long as you get the same or mostly the same back when you
| decode it again...
That was *my* original statement.
| So resampling at a lower rate for instance is not a compression as you
| don't get the original data back. ADC is not a compression as there is no
| way you can measure the size of a analog recording in bits.
Not true. On otherwise identical media, the analog recording takes up more
space than PCM sampled from the same source (LD vs. CD).
| It is a conversion, you get something else back as what you put in hence
| ADC, Analog to Digital Conversion.
And when you go back again, you get out mostly what you put in. The
process of "compression" previously described has been exhibited to the
letter.
| JPEG is a compression too, and all it does in principle is leave a lot of
| color data out of the picture as the human eye is more sensitive to contrast
| and brightness then coloring.
And as the average human ear is sensitive in the 20Hz-20kHz range but not
to the 20kHz-25kHz range, so the CD-DA sampling frequency is set to throw
out the bits of anything higher than 22.05kHz. Sony and Philips engineers
experimented with sample rates as high as 50kHz, if not higher, but decided
that a sample rate higher than 44.1kHz would have been too expensive for
the consumer market. So they are doing exactly the same thing that ATRAC
does: remove sounds that the average person cannot hear.
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