Help with all this digital stuff?

[Eric Siegerman]

On Thu, May 06, 2004 at 10:55:47AM -0400, Paul Mather wrote:
> The lower the bitrate, the more quality you throw away to
> fit things in (but the smaller the resultant encoded file size).

Be aware that this throwing-away is irreversible. [1]  Thus, as
you convert from one format to another to still another, there
*can* be generational losses, as with analog.

This isn't true of straight bit-for-bit copying (of either the
compressed or the uncompressed data); that's what has the RIAA in
such a tizzy.  But depending on the device, bit-for-bit copies
might not be possible.  E.g. with (some?) minidisc recorders, the
device does lossy compression while recording and decompresses on
playback, and that compression can't be turned off.

The way to avoid generational losses if you want to work on the
material (edit home videos, clean up clicks and pops on stuff
recorded from vinyl, etc.) is to keep it uncompressed on your
computer, or else to use only lossless compression like the
"shorten" program; and when you're finished, only then convert it
to a lossily compressed format for playback.  (And burn the
lossless version to a CD/DVD as a backup, even if it isn't
directly playable, in case you decide down the road that the
material needs more work).

[1] The technical term is "lossy compression", as opposed to
"lossless compression" as in WinZip.  Lossy compression smoothes
out fine detail, the challenge being to choose detail that is
imperceptible (or at least less perceptible) by the human nervous
system.  By very rough analogy, think of a naturalistic painting
of a cat, vs. a high-res photograph taken in good light.  The
photo will have captured every single hair.  The painter won't
have bothered, but that won't cause the viewer any trouble.  But
as the artist makes takes less effort to draw all that furry
detail, the result becomes less realistic, until you end up with
a cartoon sketch.  That's analogous to turning up the compression
level until you end up with the tinny squawk that's all that
telephones are capable of.

--

|  | /\
|-_|/  >   Eric Siegerman, Toronto, Ont.        erics at telepres.com
|  |  /
It must be said that they would have sounded better if the singer
wouldn't throw his fellow band members to the ground and toss the
drum kit around during songs.
        - Patrick Lenneau