biquad~
Two-pole, two-zero filter
Description
biquad~ implements a two-pole, two-zero filter using the following equation:
y[n] = a0 * x[n] + a1 * x[n-1] + a2 * x[n-2] - b1 * y[n-1] - b2 * y[n-2]
You can specify the coefficients a0, a1, a2, b1, and b2 as signals or floats (if you make the filter explode by making the b coefficients too high, you can recover (after lowering them) with the clear message, or by turning the audio on and off).
Arguments
a0[float]
optional
Set the initial value for the a0 filter coefficient. If a signal is connected to the second inlet, the coefficient supplied as an argument is ignored.
a1[float]
optional
Set the initial value for the a1 filter coefficient. If a signal is connected to the third inlet, the coefficient supplied as an argument is ignored.
a2[float]
optional
Set the initial value for the a2 filter coefficient. If a signal is connected to the fourth inlet, the coefficient supplied as an argument is ignored.
b1[float]
optional
Set the initial value for the b1 filter coefficient. If a signal is connected to the fifth inlet, the coefficient supplied as an argument is ignored.
b2[float]
optional
Set the initial value for the b2 filter coefficient. If a signal is connected to the sixth inlet, the coefficient supplied as an argument is ignored.
Attributes
smooth[int]: 1
Toggles the smoothing of filter coeffient changes.
Common Box Attributes
annotation[symbol]
Sets the text that will be displayed in the Clue window when the user moves the mouse over the object.
background[int]: 0
Adds or removes the object from the patcher's background layer. background 1 adds the object to the background layer, background 0 removes it. Objects in the background layer are shown behind all objects in the default foreground layer.
color[4 floats]
Sets the color for the object box outline.
fontface[int]
Sets the type style used by the object. The options are:
plain
bold
italic
bold italic
Possible values:
0 = 'regular'
1 = 'bold'
2 = 'italic'
3 = 'bold italic'
fontname[symbol]
Sets the object's font.
fontsize[float]
Sets the object's font size (in points).
Possible values:
'8'
'9'
'10'
'11'
'12'
'13'
'14'
'16'
'18'
'20'
'24'
'30'
'36'
'48'
'64'
'72'
hint[symbol]
Sets the text that will be displayed in as a pop-up hint when the user moves the mouse over the object in a locked patcher.
ignoreclick[int]: 0
Toggles whether an object ignores mouse clicks in a locked patcher.
jspainterfile[symbol]
You can override the default appearance of a user interface object by assigning a JavaScript file with code for painting the object. The file must be in the search path.
patching_rect[4 floats]: 0. 0. 100. 0.
Sets the position and size of the object in the patcher window.
position[2 floats]
write-only
Sets the object's x and y position in both patching and presentation modes (if the object belongs to its patcher's presentation), leaving its size unchanged.
presentation[int]: 0
Sets whether an object belongs to the patcher's presentation.
presentation_rect[4 floats]: 0. 0. 0. 0.
Sets the x and y position and width and height of the object in the patcher's presentation, leaving its patching position unchanged.
rect[4 floats]
write-only
Sets the x and y position and width and height of the object in both patching and presentation modes (if the object belongs to its patcher's presentation).
size[2 floats]
write-only
Sets the object's width and height in both patching and presentation modes (if the object belongs to its patcher's presentation), leaving its position unchanged.
textcolor[4 floats]
Sets the color for the object's text in RGBA format.
textjustification[int]
Sets the justification for the object's text.
Possible values:
0 = 'left'
1 = 'center'
2 = 'right'
varname[symbol]
Sets the patcher's scripting name, which can be used to address the object by name in pattr, scripting messages to thispatcher, and the js object.
Messages
int
Converted to float .
The coefficients in inlets 2 to 6 may be specified by a number instead of a signal. If a signal is also connected to the inlet, the number value is ignored.
- filter-coefficient
[int]
float
The coefficients in inlets 2 to 6 may be specified by a float instead of a signal. If a signal is also connected to the inlet, the float is ignored.
- filter-coefficient
[float]
list
The five filter coefficients can be provided as a list in the left inlet. The first number in the list is coefficient a0, the next is a1, and so on. If a signal is connected to a given inlet, the coefficient supplied in the list for that inlet is ignored.
- a0
[float]
- a1
[float]
- a2
[float]
- b1
[float]
- b2
[float]
clear
Clears the biquad~ object's memory of previous inputs and outputs, resetting xn-1, xn-2, yn-1, and yn-2 to 0.
dictionary
The word dictionary , followed by a symbol that references a named filterdesign object dictionary (set via the name attribute), will cause the biquad~ object to use the dictionary values for filter coefficients.
- dictionary-name
[symbol]
signal
In left inlet: Signal to be filtered. The filter mixes the current input sample with the two previous input samples and the two previous output samples according to the formula:
yn = a0xn + a1xn-1 + a2xn-2 - b1yn-1 - b2yn-2.
In 2nd inlet: Amplitude coefficient a0, for scaling the amount of the current input to be passed directly to the output.
In 3rd inlet: Amplitude coefficient a1, for scaling the amount of the previous input sample to be added to the output.
In 4th inlet: Amplitude coefficient a2, for scaling the amount of input sample n-2 to be added to the output.
In 5th inlet: Amplitude coefficient b1, for scaling the amount of the previous output sample to be added to the current output.
In right inlet: Amplitude coefficient b2, for scaling the amount of output sample n-2 to be added to the current output. .
stoke
The word stoke , followed by a list that specifies a set of filter coefficient values, will preload the filter so that it starts in a given initial state, allowing the filter to be used for purposes such as a ringing oscillator.
- a0
[float]
- a1
[float]
- a2
[float]
- b1
[float]
- b2
[float]
Output
signal
The filtered signal.
See Also
| Name | Description |
|---|---|
| buffir~ | buffer-based FIR filter |
| cascade~ | Cascaded series of biquad filters |
| comb~ | Apply a comb filter effect |
| cross~ | Third-order crossover filter |
| filtercoeff~ | Signal-rate filter coefficient generator |
| filtergraph~ | Filter editor |
| lores~ | Resonant lowpass filter |
| onepole~ | Single-pole lowpass filter |
| reson~ | Resonant bandpass filter |
| svf~ | State-variable filter with simultaneous outputs |
| teeth~ | Comb filter with feedforward and feedback delay control |