The min, max, and average values are calculated from per-window RMS values. The audio selection is divided into a series of overlapping windows, and for each window, the per-window RMS value is calculated as follows: for each sample in the window, square the amplitude and add to an accumulator; afterwards, take the square root of the accumulated sum divided by the window's sample count. The statistics are then updated from each resulting per-window RMS value, as follows:
Min: the minimum of all the per-window RMS values
Max: the maximum of all the per-window RMS values
Average: the average of all the per-window RMS values (sum of the per-window RMS values divided by the number of windows)
The "Total" statistic is calculated directly from the samples, not from the per-window RMS values, hence the slight difference, but the method is similar: for each sample in the entire selection, square the amplitude and add to an accumulator; afterwards, take the square root of the accumulated sum divided by the total sample count. Basically the Average and Total values differ because of the nature of averaging; neither is more or less "correct".
Hope that helps.
ck [PS: I assume you were referring to Average vs. Total RMS; I'm not aware of a value labeled "Peak RMS" anywhere in WaveShop.]
Last edit: Chris Korda 2013-06-19
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Hi there,
I would like to know how the two RMS values are calculated, as I am curious why they differ.
Thanks,
JSS
The min, max, and average values are calculated from per-window RMS values. The audio selection is divided into a series of overlapping windows, and for each window, the per-window RMS value is calculated as follows: for each sample in the window, square the amplitude and add to an accumulator; afterwards, take the square root of the accumulated sum divided by the window's sample count. The statistics are then updated from each resulting per-window RMS value, as follows:
Min: the minimum of all the per-window RMS values
Max: the maximum of all the per-window RMS values
Average: the average of all the per-window RMS values (sum of the per-window RMS values divided by the number of windows)
The "Total" statistic is calculated directly from the samples, not from the per-window RMS values, hence the slight difference, but the method is similar: for each sample in the entire selection, square the amplitude and add to an accumulator; afterwards, take the square root of the accumulated sum divided by the total sample count. Basically the Average and Total values differ because of the nature of averaging; neither is more or less "correct".
Hope that helps.
ck
[PS: I assume you were referring to Average vs. Total RMS; I'm not aware of a value labeled "Peak RMS" anywhere in WaveShop.]
Last edit: Chris Korda 2013-06-19
Yes, I did mean Average vs Total RMS, Max RMS would be what I meant by 'peak'. Can the title be changed, in case others have the same question?
Thanks for the explanation!
JSS
Last edit: John Spencer 2013-06-20