IIRFilterNode.getFrequencyResponse()
The getFrequencyResponse()
method of the IIRFilterNode
interface takes the current filtering algorithm's settings and calculates the frequency response for frequencies specified in a specified array of frequencies.
The two output arrays, magResponseOutput
and phaseResponseOutput
, must be created before calling this method; they must be the same size as the array of input frequency values (frequencyArray
).
Syntax
IIRFilterNode.getFrequencyResponse(frequencyArray, magResponseOutput, phaseResponseOutput);
Parameters
frequencyArray
- A
Float32Array
containing an array of frequencies, specified in Hertz, which you want to filter. magResponseOutput
- A
Float32Array
to receive the computed magnitudes of the freqency response for each frequency value in thefrequencyArray
. phaseResponseOutput
- A
Float32Array
to receive the computed phase response values in radians for each frequency value in the inputfrequencyArray
.
Return value
Exceptions
NotSupportedError
- The three arrays provided are not all of the same length.
Example
In the following example we are using an IIR filter on a media stream (for a complete full demo, see our stream-source-buffer demo live, or read its source.) As part of this demo, we get the frequency responses for this IIR filter, for five sample frequencies. We first create the Float32Array
objects we need, one containing the input frequencies, and two to receive the output magnitude and phase values:
var myFrequencyArray = new Float32Array(5); myFrequencyArray[0] = 1000; myFrequencyArray[1] = 2000; myFrequencyArray[2] = 3000; myFrequencyArray[3] = 4000; myFrequencyArray[4] = 5000; var magResponseOutput = new Float32Array(5); var phaseResponseOutput = new Float32Array(5);
Next we create a <ul>
element in our HTML to contain our results, and grab a reference to it in our JavaScript:
<p>IIR filter frequency response for: </p> <ul class="freq-response-output"> </ul>
var freqResponseOutput = document.querySelector('.freq-response-output');
Finally, after creating our filter, we use getFrequencyResponse()
to generate the response data and put it in our arrays, then loop through each data set and output them in a human-readable list at the bottom of the page:
var feedforwardCoefficients = [0.1, 0.2, 0.3, 0.4, 0.5]; var feedbackCoefficients = [0.5, 0.4, 0.3, 0.2, 0.1]; var iirFilter = audioCtx.createIIRFilter(feedforwardCoefficients, feedbackCoefficients); ... function calcFrequencyResponse() { iirFilter.getFrequencyResponse(myFrequencyArray, magResponseOutput, phaseResponseOutput); for(i = 0; i <= myFrequencyArray.length-1;i++){ var listItem = document.createElement('li'); listItem.innerHTML = '<strong>' + myFrequencyArray[i] + 'Hz</strong>: Magnitude ' + magResponseOutput[i] + ', Phase ' + phaseResponseOutput[i] + ' radians.'; freqResponseOutput.appendChild(listItem); } } calcFrequencyResponse();
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'getFrequencyResponse()' in that specification. |
Working Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 49 | 50 (50) | No support | ? | ? |
Feature | Android | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|
Basic support | ? | 50.0 (50) | ? | ? | ? | ? | 49.0 |
See also
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/iirfilternode/getfrequencyresponse