stream-audio-level/dist/index.js

Watch MediaStream audio level

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.watchStreamAudioLevel = void 0;
const averageFreqData = (bin, sampleRate, minHz, maxHz) => {
    let sum = 0;
    let n = 0;
    const binCount = bin.length;
    for (let i = 0; i < binCount; i++) {
        const hz = (i * sampleRate) / binCount;
        if (minHz !== undefined && hz < minHz) {
            continue;
        }
        if (maxHz !== undefined && hz > maxHz) {
            continue;
        }
        sum += bin[i];
        n++;
    }
    const average = sum / n;
    return average;
};
const maxFreqData = (bin, sampleRate, minHz, maxHz) => {
    let maxVal = -Infinity;
    const binCount = bin.length;
    for (let i = 0; i < binCount; i++) {
        if (maxVal < bin[i]) {
            const hz = (i * sampleRate) / binCount;
            if (minHz !== undefined && hz < minHz) {
                continue;
            }
            if (maxHz !== undefined && hz > maxHz) {
                continue;
            }
            maxVal = bin[i];
        }
    }
    return maxVal;
};
exports.watchStreamAudioLevel = (stream, onUpdate, opt) => {
    const calcMethod = (opt && opt.calcMethod) || 'average';
    const valueType = (opt && opt.valueType) || 'byte';
    const AudioContext = window.AudioContext || window.webkitAudioContext;
    const audioContext = new AudioContext();
    const analyser = audioContext.createAnalyser();
    const mediaStreamSource = audioContext.createMediaStreamSource(stream);
    const processor = audioContext.createScriptProcessor(2048, 1, 1);
    analyser.smoothingTimeConstant = (opt && opt.smoothingTimeConstant) || 0.1;
    analyser.fftSize = (opt && opt.fftSize) || 512;
    mediaStreamSource.connect(analyser);
    analyser.connect(processor);
    processor.connect(audioContext.destination);
    const calcF = calcMethod === 'average' ? averageFreqData : maxFreqData;
    const getFreqData = () => {
        if (valueType === 'byte') {
            const bin = new Uint8Array(analyser.frequencyBinCount);
            analyser.getByteFrequencyData(bin);
            return bin;
        }
        const bin = new Float32Array(analyser.frequencyBinCount);
        analyser.getFloatFrequencyData(bin);
        return bin;
    };
    const handler = () => {
        const bin = getFreqData();
        const v = calcF(bin, audioContext.sampleRate, opt && opt.minHz, opt && opt.maxHz);
        onUpdate(v);
    };
    processor.onaudioprocess = handler;
    return () => {
        processor.removeEventListener('audioprocess', handler);
        analyser.disconnect(processor);
        processor.disconnect(audioContext.destination);
        mediaStreamSource.disconnect(analyser);
        audioContext.close();
    };
};
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