Programmer Guide/SPU Reference/RMSB

RMSB - frequency band rms

Usage:

RMSB X SR DEF P1 P2 P3 REF TYP TABLE COL WIN DBREF

Inputs:

X	amplitude spectrum vector (linear!!!)
SR	sampling rate in Hz
DEF	type of band/frequency definition {Direct, Equal, Geometric}
P1,P2,P3	band definitions parameters (depends on DEF - see table below)
REF	Absolute, Band|Relative}
TYP	type of rms output values {Power, LInear, LOgarithmic}
TABLE	name of parameter table
COL	1st column for rms values in output table
WIN	either a number (length of signal window) or a vector (length = length of signal window)
DBREF	reference value for logarithmic output

Outputs:

Y	band rms values

Function:

This function computes the energy in different frequency bands of the spectrum X. The input X must be a magnitude spectrum (linear magnitudes) with an equally spaced frequency scale and a frequency range from 0 to SR/2 (e.g. an fft spectrum). The energy bands are defined by the inputs DEF and P1-P3 in the following manner:

Table 20: Frequency band definitions selected by input DEF

value of DEF	P1	P2	P3	description
0 or DIRECT	fmin1 ...fminn	fmax1 ...fmaxn	-	The energy in the frequency bands [fmin1,fmax1] .. [fminn,fmaxn] is computed. Overlapping bands are possible.
1 or EQUAL	fmin	fmax	n	The frequency range [fmin,fmax] is split into n bands with equal bandwidth b=(fmax-fmin)/n. The boundaries of the n frequency bands are set to [fmin+i.b, fmin+(i+1).b] (with: i=0,..,n-1)
2 or GEOMETRIC	fmin	fmax	n	The frequency range [fmin,fmax] is split into n bands with constant bandwidth ratio q=(fmax/fmin)1/n. The boundaries of the n frequency bands are set to [fmin.qi, fmin.q(i+1)] (with: i=0,..,n-1)

To compute the energy in a frequency band the squared magnitudes inside the band are added. The input REF can be used to compute relative or absolute energy values.

Table 21: Compute relative or absolute rms values

value of REF	energy computation
0, 1, FULL orABSOLUTE	The energy ei is the sum of all aj2 with frequency fj is inside the band i.
2, 3, BAND orRELATIVE	The energy ei is computed as described above and than multiplied with k=2/SR.bi. This mode can be used to compute the energy density in a band.

Before the computed energy values are stored in the output Y, they are converted according to the value of input TYP.

Table 22: Type of output values

value of TYP	value stored in Y (and in the table columns)
0 or POWER	energy values ei as computed
1 or LINEAR	ei1/2
2 or LOGARITHMIC	10.log10(ei)

If a table (defined by TABLE and COL) is specified, the values are also stored in the columns COL to COL+n-1 of the table. In each evaluation cycle the columns of one entry are filled (starting at entry 0).