Fw: [LAD] Total and Agerage RMS power calculation - Linux-audio-dev

25 Jun 2007

Hi,
Thanks for mail.
...
 Your terminology is not very clear. What exactly do you
mean by
'average' RMS and 'max' RMS ? The 'M' in RMS stands for
'mean',
so it is already an average over all samples considered, and 
I'm using 25ms of window for calculating Max RMS,meaning is in
every 25 ms I calculate RMS and compare it with previous value 
if current 25 ms RMS value is bigger than previous value I retain
this value, using this I find MAX RMS value for 25ms in file and call
it MAX RMS value as it is in adobe audition.

...
 That is, by definition of RMS = square Root of the Mean
of the 
Squares, the RMS value of the N samples, expressed in the same
unit as the samples themselves.  
...
  >AvgRMS = 20.0 * log10 ( rms /2^N-1) 
...
 You may be confusing two values of N here, the first
being the
number of samples, as in equation (1), and the second being
the number of bits. 
Sorry for confusion in dB conversion algorithm, it is surely
depth  of sample in number of bits.

...
  normalised_rms = rms / (2^(B-1))
and then convert to dB:
 normalised_rms_in_dB = 20 * log10 (normalised_rms). 
your are right here as i'm also doing the same. My requirement is
like  Adobe audition my application has to calculate the Average RMS power
for a wave audio file using time window system.
 I'm trying to do the same to calculate the Average RMS but confusion is  my 
calculated Avrg RMS value matches with Total RMS  value  of the adobe edition.
How to calculate the Average RMS , if above algorithm calculates Total RMS.

BR
chandrashekhar 

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