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).