Translation between dbFS and Sample level

M

mattd

New member
I've got ProTools 7.

When I'm looking at a wave file on the main tracks display, I can move the cursor around inside the wave file. If I move the cursor left or right, a readout at the top of the window will tell me the exact time displacement in terms of measures/beats/fractions of beats. Fine. If I move the cursor up and down, another readout will tell me the value of the sample, which ranges any where from -32K to 32K.

What I want to know is how to translate the sample value into dbFS level. So, if one sample is 12K, is that -10dbFS? -16dbFS?

What's the formula?
 
probably easier to change vertical scale format display and simply zoom in to compare . . . if all you want is a rough idea of samples to dB

and formula does depend on bit dept of samples for 16 bit 0dB would correspond to 32767 sample with -6 db would be half that . .. if using 'float' (probably not something possible with PT) 0dB is 1 -6 db is .5

conversion is problematic as dB is a ratio, a logarithmic measure of a signals value relative to maximum value it can contain well actual formula, for 16 bit integer (easier to calculate in floating point, is something like: 20 * log10 (x / 32767) = dB where x is the specific sample value (and i will freely admit that I might have overlooked something rudimentary & significant in the formula . . . was kind of reasoning to get to it as I posted the rest of the stuff
 
Wouldn't it be simpler to play the track and look at the meters?


This seems like an extremely complicated way of trying to figure out what the level of each individual sample is. And how would knowing what each individual sample's dBFS value is help you?
 
The reason I want to know is curiosity -- I like to know what's going on under the hood, so to speak.

I was zooming in on a wave file and it occurred to me that samples didn't correspond linearly to dbFS. So, it seemed like it was some kind of exponential relationship, but not entirely clear what the numbers were.

The 20 * log(x/32K) seems to be the answer I was looking for. Thanks all for your help.

And as for changing the vertical scale, how is this done? I looked around in the manual and couldn't find it.
 
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