twilio-video/es5/webaudio/workaround180748.js

Twilio Video JavaScript Library

'use strict';
var detectSilence = require('./detectsilence');
/**
 * This function attempts to workaround WebKit Bug 180748. It does so by
 *
 *   1. Calling `getUserMedia`, and
 *   2. Checking to see if the resulting MediaStream is silent.
 *   3. If so, repeat Step 1; otherwise, return the MediaStream.
 *
 * The function only repeats up to `n` times, and it only waits `timeout`
 * milliseconds when detecting silence. Assuming `getUserMedia` is
 * instantaneous, in the best case, this function returns a Promise that
 * resolves immediately; in the worst case, this function returns a Promise that
 * resolves in `n` * `timeout` milliseconds.
 *
 * @param {Log} log
 * @param {function(MediaStreamConstraints): Promise<MediaStream>} getUserMedia
 * @param {MediaStreamConstraints} constraints
 * @param {number} [n=3]
 * @param {number} [timeout=250]
 * @returns Promise<MediaStream>
 */
function workaround(log, getUserMedia, constraints, n, timeout) {
    n = typeof n === 'number' ? n : 3;
    var retry = 0;
    // NOTE(mroberts): We have to delay require-ing AudioContextFactory, because
    // it exports a default instance whose constructor calls Object.assign.
    var AudioContextFactory = require('./audiocontext');
    var holder = {};
    var audioContext = AudioContextFactory.getOrCreate(holder);
    /**
     * We can't use async/await yet, so I need to factor this out.
     * @returns {Promise<MediaStream>}
     */
    function doWorkaround() {
        return getUserMedia(constraints).then(function (stream) {
            var isSilentPromise = constraints.audio
                ? detectSilence(audioContext, stream, timeout).catch(function (err) {
                    log.warn('Encountered an error while detecting silence', err);
                    return true;
                })
                : Promise.resolve(false);
            return isSilentPromise.then(function (isSilent) {
                if (!isSilent) {
                    log.info('Got a non-silent audio MediaStreamTrack; returning it.');
                    return stream;
                }
                else if (n <= 0) {
                    log.warn('Got a silent audio MediaStreamTrack. Normally we would try \
to get a new one, but we\'ve run out of retries; returning it anyway.');
                    return stream;
                }
                log.warn("Got a silent audio MediaStreamTrack. Stopping all MediaStreamTracks and calling getUserMedia again. This is retry #" + ++retry + ".");
                stream.getTracks().forEach(function (track) { return track.stop(); });
                n--;
                return doWorkaround();
            });
        });
    }
    return doWorkaround().then(function (stream) {
        AudioContextFactory.release(holder);
        return stream;
    }, function (error) {
        AudioContextFactory.release(holder);
        throw error;
    });
}
module.exports = workaround;
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