EQ()

EQ

Equalizer instrument (peak/notch, shelving and high/low pass filter).

in RTcmix/insts/jg

quick syntax:

EQ(outsk, insk, dur, AMP, EQTYPE, inputchan, PAN, BYPASS, FILTFREQ, FILTQ[, FILTAMP])

CAPITALIZED parameters are pfield-enabled for table or dynamic control (see the maketable or makeconnection scorefile commands). Parameters after the [bracket] are optional and default to 0 unless otherwise noted.

Param Field	Parameter	Units	Dynamic	Optional	Notes
p0	output start time	seconds	no	no
p1	input start time	seconds	no	no
p2	input duration	seconds	no	no
p3	amplitude multiplier	relative multiplier of input signal	yes	no
p4	EQ type	“lowpass”, “highpass”, “lowshelf”, “highshelf”, “peaknotch”; or numeric codes for the EQ type (0: lowpass, 1: highpass, 2: lowshelf, 3: highshelf, 4: peaknotch	yes*	no	* only dynamic when using numeric codes
p5	input channel	-	no	no
p6	pan	0-1 stereo; 0.5 is middle	yes	no
p7	bypass filter	0: bypass off, 1: bypass on	yes	no	usually use 0
p8	filter frequency	Hz	yes	no
p9	filter Q	values from 0.5 to 10.0, roughly	yes	no
p10	filter gain	dB	yes	yes	shelf and peak/notch only

Parameters labled as Dynamic can receive dynamic updates from a table or real-time control source.

Author: John Gibson, 7 Dec 2003; rev for v4, 7/23/04 Based on formulas by Robert Bristow-Johnson (“Audio-EQ-Cookbook”) and code by Tom St Denis (see musicdsp.org)

EQ is an “equalizer” (another name for “filter”) instrument able to instantiate several different types of audio filters.

Usage Notes

EQ can be set to do several different types of filters (peak/notch, shelving and high/low pass types), depending on the setting of p4 (“EQTYPE”).

A standard ‘biquad’ DSP filter algorithm is used to build these different types of filters.

In addition to the filter frequency and gain, the ‘Q’ (“FILTQ”, p9) can be used to determine how ‘steep’ the filter will be. Filter parameters are interpreted depening on what type of filter (p4) is selected.

The MULTEQ instrument allows for the processing of multiple bands, each (up to 8) a separate instantiation of EQ.

The output of EQ can be either mono or stereo.

Sample Scores

very basic:

   rtsetparams(44100, 2)
   load("EQ")
   
   rtinput("mystereofile.wav")
   inskip = 0
   dur = DUR()
   amp = 0.6
   bypass = 0
   type = "lowshelf"
   freq = 500
   Q = 3.0
   gain = 6.0
   
   EQ(0, inskip, dur, amp, type, 0, 1, bypass, freq, Q, gain)
   EQ(0, inskip, dur, amp, type, 1, 0, bypass, freq, Q, gain)

slightly more advanced:

   rtsetparams(44100, 2)
   load("EQ")
   
   rtinput("mysound.aiff")
   inskip = 0
   dur = DUR()
   
   start = 2
   amp = 1
   bypass = 0
   
   //type = "lowpass"
   type = "highpass"
   //type = "lowshelf"
   //type = "highshelf"
   //type = "peaknotch"
   
   pan = maketable("line", 100, 0,1, 1,0)
   freq = makeconnection("mouse", "x", min=200, max=2000, dflt=min, lag=50,
            "freq", "Hz", 1)
   Q = 1.0
   gain = makeconnection("mouse", "y", min=-30, max=20, dflt=0, lag=50,
            "gain", "dB", 1)
   
   EQ(start, inskip, dur, amp, type, inchan=0, pan, bypass, freq, Q, gain)

EQ

quick syntax:

Usage Notes

Sample Scores

See Also