Re: [LAD] Calculate R M S

  Tnx a lot @ all for great info.
> loudness to ITU/EBU standards at the next LAC (if the paper is
> accepted).
>
> Some filtering followed by RMS detection will provide a good
> approximation to subjective loudness.
 It  means block schema of Automatick Gain/Volume Control is (can
 be)
 Filter -- RMS_Calculator -- Volume_control 
 In exact such order ?
 (- For example in FFT are used Rectangular(no window) , Hann,
 Hamming, Barlow ... windows. -)
 What are the most common filters for ACG and "Loudness" control ?
> > How to calculate RMS with hi-precision for frequencies > 10
> kHz ?
> > With inerpolation or so ?
>
> Nothing special is needed for high frequencies.
 Why not ?
 So far i unterstand the best way for RMS calc would be SQRT of
 integral of power2 of sound signal function.
 Real signal is not sequence of sampled rectangles, but smooth
 function.
 Can not happen so what that rectangle inaccuracy of each sample by
 freq > 10KHZ ,
 in end effect will accumulate big inaccuracy ?
> > What is reference ( 0dB ) RMS for example for 16bit PCM
> signal 1024
> > samples ?
>
> Normally to do the calculations you convert first to floating point
> in the range +/- 1.0. If you read a file libsndfile will do that
> for
> you, for realtime if you use Jack all samples are already in that
> format.
>
> The reference for dB is what you make it. Normally full scale for a
> sine wave is set to '0 dB' The EBU 'target' loudness is -23 dB on
> that scale (which is quite low for most popular music, but probably
> OK for general purpose use).
 U mean that normally full amplitude sine wave is defined as 0dB RMS
 signal ?
 Can U plz gimme some examples ?
 What is RMS value dB of  +/-maximum_angular signal 
 _-_-_-_-_-
 ( such values - 4k times 0x8000 and 4k times 0x7FFF  .... ) ?
 What is RMS value dB of  sine wave , peak/amplitude normalized
 to 0x8000-0x7FFF  (or 1.0) ?
  Tnx in Advance
 Alfs Kurmis.
  ----

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Received on Fri Feb 18 20:15:04 2011