twilio-video/es5/webaudio/detectsilence.js

Twilio Video JavaScript Library

'use strict';
/**
 * Return a Promise that resolves after `timeout` milliseconds.
 * @param {?number} [timeout=0]
 * @returns {Promise<void>}
 */
function delay(timeout) {
    timeout = typeof timeout === 'number' ? timeout : 0;
    return new Promise(function (resolve) { return setTimeout(resolve, timeout); });
}
/**
 * Attempt to detect silence. The Promise returned by this function returns
 * false as soon as audio is detected or true after `timeout` milliseconds.
 * @param {AudioContext} audioContext
 * @param {MediaStream} stream
 * @param {?number} [timeout=250]
 * @returns {Promise<boolean>}
 */
function detectSilence(audioContext, stream, timeout) {
    timeout = typeof timeout === 'number' ? timeout : 250;
    var source = audioContext.createMediaStreamSource(stream);
    var analyser = audioContext.createAnalyser();
    analyser.fftSize = 2048;
    source.connect(analyser);
    var samples = new Uint8Array(analyser.fftSize);
    var timeoutDidFire = false;
    setTimeout(function () { timeoutDidFire = true; }, timeout);
    /**
     * We can't use async/await yet, so I need to factor this out.
     * @returns {Promise<boolean>}
     */
    function doDetectSilence() {
        if (timeoutDidFire) {
            return Promise.resolve(true);
        }
        analyser.getByteTimeDomainData(samples);
        // NOTE(mpatwardhan): An audio MediaStreamTrack can be silent either due to all samples
        // being equal to 128 or all samples being equal to 0.
        return samples.some(function (sample) { return sample !== 128 && sample !== 0; })
            ? Promise.resolve(false)
            : delay().then(doDetectSilence);
    }
    return doDetectSilence().then(function (isSilent) {
        source.disconnect();
        return isSilent;
    }, function (error) {
        source.disconnect();
        throw error;
    });
}
module.exports = detectSilence;
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