forked from Mirrors/freeswitch
97 lines
3.2 KiB
JavaScript
97 lines
3.2 KiB
JavaScript
/*
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The MIT License (MIT)
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Copyright (c) 2014 Chris Wilson
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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/*
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Usage:
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audioNode = createAudioMeter(audioContext,clipLevel,averaging,clipLag);
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audioContext: the AudioContext you're using.
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clipLevel: the level (0 to 1) that you would consider "clipping".
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Defaults to 0.98.
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averaging: how "smoothed" you would like the meter to be over time.
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Should be between 0 and less than 1. Defaults to 0.95.
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clipLag: how long you would like the "clipping" indicator to show
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after clipping has occured, in milliseconds. Defaults to 750ms.
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Access the clipping through node.checkClipping(); use node.shutdown to get rid of it.
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*/
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function createAudioMeter(audioContext,clipLevel,averaging,clipLag) {
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var processor = audioContext.createScriptProcessor(512);
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processor.onaudioprocess = volumeAudioProcess;
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processor.clipping = false;
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processor.lastClip = 0;
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processor.volume = 0;
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processor.clipLevel = clipLevel || 0.98;
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processor.averaging = averaging || 0.95;
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processor.clipLag = clipLag || 750;
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// this will have no effect, since we don't copy the input to the output,
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// but works around a current Chrome bug.
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processor.connect(audioContext.destination);
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processor.checkClipping =
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function(){
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if (!this.clipping)
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return false;
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if ((this.lastClip + this.clipLag) < window.performance.now())
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this.clipping = false;
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return this.clipping;
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};
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processor.shutdown =
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function(){
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this.disconnect();
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this.onaudioprocess = null;
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};
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return processor;
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}
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function volumeAudioProcess( event ) {
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var buf = event.inputBuffer.getChannelData(0);
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var bufLength = buf.length;
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var sum = 0;
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var x;
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// Do a root-mean-square on the samples: sum up the squares...
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for (var i=0; i<bufLength; i++) {
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x = buf[i];
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if (Math.abs(x)>=this.clipLevel) {
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this.clipping = true;
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this.lastClip = window.performance.now();
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}
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sum += x * x;
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}
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// ... then take the square root of the sum.
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var rms = Math.sqrt(sum / bufLength);
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// Now smooth this out with the averaging factor applied
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// to the previous sample - take the max here because we
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// want "fast attack, slow release."
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this.volume = Math.max(rms, this.volume*this.averaging);
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}
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