Mike Rivers writes:
On 11/19/2010 10:22 AM, Randy Yates wrote:
Mike writes:
dBFS is a peak level.
That's not the way I understand it. Am I wrong? It's
no different than dBu or dBV - just a different "reference"
level. Thus it would be an RMS measure.
We're getting wrapped around the axle here since I don't know what
your real question is. What you're asking is kind of abstract.
Is dBFS abstract? If so, then I guess I'm asking an abstract
question.
My question is this: What is the definition of dBFS?
dBFS is dB referenced to full scale which is all the bits on
dBu is dB referenced to .775 volts
dBV is dB referenced to 1 volt
Any of those can be RMS or peak.
Peak is significant when dealing with digital levels, but the only
level that's really significant is the one beyond which you can't go
higher, and that's only one level, 0 dBFS
If dBFS is defined as
dBFS = 20 * log_10(XRMS / (RMS value of full-scale sine wave),
where XRMS is the RMS value of the digital data stream, and you're
generating a "digital square wave," then you are wrong. The digital
square wave can go to +3dBFS as defined above.
So you're saying then it's FS sine.
If you say so. Please ask your REAL question if you have one. Are you
looking for a solution to a problem? Or trying to interpret some
marketing goof's data sheet or manual? If you're just looking for
definitions and conventions, then you have them.
It seems that there really is no standard definition. That's the
problem. It's not a matter of abstractness, but rather of
well-definedness.
--
Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven.
Digital Signal Labs % She love the way Puccini lays down a tune, and
% Verdi's always creepin' from her room."
http://www.digitalsignallabs.com % "Rockaria", *A New World Record*, ELO