Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!malcolm
From: malcolm@Apple.COM (Malcolm Slaney)
Newsgroups: comp.dsp
Subject: Digital Output and VU meters
Keywords: digital, DA, VU, video
Message-ID: <50010@apple.Apple.COM>
Date: 8 Mar 91 01:53:08 GMT
Organization: Apple Computer Inc., Cupertino, CA
Lines: 21

OK, now for something different....I won't mention the words Ny**ist or
ov**samp****....  This isn't all digital but wreck.audio seems hopeless.

I have a bunch of digital sounds (both 8 and 16 bit) and I often copy
them onto video tape.  I was recently copying a tape and it was preceeded
by color bars with a 0dB tone.  That made it real easy to set the input 
level on the other deck....just match the 0dB.

So, now I want to do the equivalent thing with the digital audio that I'm
dubbing onto video tape.  The question is....what digital levels would
best correspond to 0dB?  Should I put in a full-scale sine wave at some
frequency and assume that my real signals will be ok?  Most of my digital 
samples are full-scale speech.  (i.e. they are scaled just enough so they 
don't clip.)   I don't understand VU meters and tape saturation well enough
to know where to start.

Perhaps it makes sense to find the peak power in my full-scale digital
speech signals, and then generate a sine wave with the same power and call
that 0dB.  What do people think?

								Malcolm