Re: [AV Media Matters] Digitizing Audio and Video-ReallyBigPost

[Jim Wheeler <Jimwheeler@aol.com>]

Alyssa

There is NO way that spinning or not spinning a disk can effect the
level of 
magnetism of a disk.  I wonder where that idea came from?

Also, the spinning video heads on a videotape recorder are fixed in the 
scanner and do NOT move!  I ran an experimental scanner at 800 rps and
nothing went 
wrong.  Think about that; in a single second, that scanner made 800 
revolutions!  Most scanners run at a very slow speed of about 30 rps.  

Be careful with information from someone who is speaking out of their
field.  
There are many "old wives tales" that keep getting repeated.  

Computer tapes do not use redundant recording because that would double
the 
amount of data to be recorded.  Instead, error correction is used.  At
Ampex, 
we were using Miller-squared error correction about 30 years ago and
then 
Reed-Solomon about 20 years ago.  New error correction algorithms are
always being 
developed. The Ampex digital videotape machines I helped design, all
have 
about three layers of error correction.   

As a test, I removed about a square inch of oxide.  During playback, I
had to 
look at a large monitor in a dimly lit room to see the area with no 
recording.  That demo convinced me that digital recording was here to
stay.

DAT is a consumer format so DAT machines do not have sophisticated error

correction.  DataTapes use sophisticated error correction because they
MUST 
preserve the data of banks, insurance companies, etc.

BEST

Jim Wheeler

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