Hi all,
I noticed a recent thread in Nabble's Csound-General list
regarding 0dbfs and clipping, which prompted a related
concern of mine.  As I'm not subscribed to that list
[too many lists already...] I'd like to bring it up here.

It seems to me that the 0dbfs scheme was designed in
the days when most or all output was integer, but I'm
not sure it is being applied to float values in the
best way.

When you are working to a maximum integer limit that
can't be exceeded, it seems right to be able to set
0dbfs to the level that corresponds to that limit,
so that generated signals can be scaled to that, and
you get warned if it is exceeded.

However, I find that the 0dbfs setting is also used to
scale floating output values -- so that the level
correponding to '0' dbfs is always rescaled to '1.000'.
When this output is going to a mixer -- as is usual in
real-time preformance, I guess -- it can be frustrating
because this may be insufficient to get a decent final
level, unless all the faders in the chain are set to
maximum.

In practice I overcome this by using a 0dbfs of less
than 1, but as a consequence I get many many "out of
range" messages.  It was a while before I realized
that these were totally meaningless!  Only the levels
*after* the mixer chain are relevant to clipping and
distortion.

I think there ought to be some decoupling here.
One solution would be to *not* scale floating output
by 0dbfs.  That setting would represent only a 'desired
limit': any higher signal would just trigger an 'out of
range' report, but would not be clipped or scaled.
Then one could set the signal levels in the csd to
whatever will give a suitable level to send to the mixer.

Alternatively, there could be either a new 'scaling'
system variable, or a command option to set the scale.
0dbfs would then continue to scale to 1.000, but the
scaling factor would be applied after that, to raise
the actual output to a suitable level.

What do you think?

	-- Pete --
	

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