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    BiquadFilterNode

    The BiquadFilterNode interface represents a simple low-order filter, and is created using the AudioContext.createBiquadFilter() method. It is an AudioNode that can represent different kinds of filters, tone control devices, and graphic equalizers. A BiquadFilterNode always has exactly one input and one output.

    • Number of inputs 1
    • Number of outputs 1
    • Channel count mode "max"
    • Channel count 2 (not used in the default count mode)
    • Channel interpretation "speakers"

    Properties

    Inherits properties from its parent, AudioNode.

    BiquadFilterNode.frequency Read only
    Is a k-rate AudioParam, a double representing a frequency in the current filtering algorithm measured in hertz (Hz).
    BiquadFilterNode.detune Read only
    Is an a-rate AudioParam representing detuning of the frequency in cents.
    BiquadFilterNode.Q Read only
    Is a k-rate AudioParam, a double representing a Q factor, or quality factor.
    BiquadFilterNode.gain Read only
    Is a k-rate AudioParam, a double representing the gain used in the current filtering algorithm.
    BiquadFilterNode.type
    Is a string value defining the kind of filtering algorithm the node is implementing.
     
    The meaning of the different parameters depending of the type of the filter (detune has the same meaning regardless, so isn't listed below)
    type Description frequency Q gain
    lowpass Standard second-order resonant lowpass filter with 12dB/octave rolloff. Frequencies below the cutoff pass through; frequencies above it are attenuated. The cutoff frequency. Indicates how peaked the frequency is around the cutoff. The greater the value is, the greater is the peak. Not used
    highpass Standard second-order resonant highpass filter with 12dB/octave rolloff. Frequencies below the cutoff are attenuated; frequencies above it pass through. The cutoff frequency. Indicates how peaked the frequency is around the cutoff. The greater the value, the greater the peak. Not used
    bandpass Standard second-order bandpass filter. Frequencies outside the given range of frequencies are attenuated; the frequencies inside it pass through. The center of the range of frequencies. Controls the width of the frequency band. The greater the Q value, the smaller the frequency band. Not used
    lowshelf Standard second-order lowshelf filer. Frequencies lower than the frequency get a boost, or an attenuation; frequencies over it are unchanged. The upper limit of the frequencies getting a boost or an attenuation. Not used The boost, in dB, to be applied; if negative, it will be an attenuation.
    highshelf Standard second-order highshelf filer. Frequencies higher than the frequency get a boost or an attenuation; frequencies lower than it are unchanged. The lower limit of the frequencies getting a boost or an attenuation. Not used The boost, in dB, to be applied; if negative, it will be an attenuation.
    peaking Frequencies inside the range get a boost or an attenuation; frequencies outside it are unchanged. The middle of the frequency range getting a boost or an attenuation. Controls the width of the frequency band. The greater the Q value, the smaller the frequency band. The boost, in dB, to be applied; if negative, it will be an attenuation.
    notch Standard notch filter, also called a band-stop or band-rejection filter. It is the opposite of a bandpass filter: frequencies outside the give range of frequencies pass through; frequencies inside it are attenuated. The center of the range of frequencies. Controls the width of the frequency band. The greater the Q value, the smaller the frequency band. Not used
    allpass Standard second-order allpass filter. It lets all frequencies through, but changes the phase-relationship between the various frequencies. The frequency with the maximal group delay, that is, the frequency where the center of the phase transition occurs. Controls how sharp the transition is at the medium frequency. The larger this parameter is, the sharper and larger the transition will be. Not used

    Methods

    Inherits methods from its parent, AudioNode.

    BiquadFilterNode.getFrequencyResponse()
    From the current filter parameter settings this method calculates the frequency response for frequencies specified in the provided array of frequencies.

    Example

    The following example shows basic usage of an AudioContext to create a Biquad filter node. For a complete working example, check out our voice-change-o-matic demo (look at the source code too).

    var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
    
    //set up the different audio nodes we will use for the app
    var analyser = audioCtx.createAnalyser();
    var distortion = audioCtx.createWaveShaper();
    var gainNode = audioCtx.createGain();
    var biquadFilter = audioCtx.createBiquadFilter();
    var convolver = audioCtx.createConvolver();
    
    // connect the nodes together
    
    source = audioCtx.createMediaStreamSource(stream);
    source.connect(analyser);
    analyser.connect(distortion);
    distortion.connect(biquadFilter);
    biquadFilter.connect(convolver);
    convolver.connect(gainNode);
    gainNode.connect(audioCtx.destination);
    
    // Manipulate the Biquad filter
    
    biquadFilter.type = "lowshelf";
    biquadFilter.frequency.value = 1000;
    biquadFilter.gain.value = 25;

    Specifications

    Specification Status Comment
    Web Audio API
    The definition of 'BiquadFilterNode' in that specification.
    Working Draft  

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support 10.0webkit 25.0 (25.0)  Not supported 15.0webkit
    22 (unprefixed)
    6.0webkit
    Feature Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
    Basic support ? 26.0 1.2 ? ? ? 33.0

    See also

    Document Tags and Contributors

    Last updated by: teoli,