@l5i/dashjs/src/streaming/rules/SwitchRequestHistory.js

A reference client implementation for the playback of MPEG DASH via Javascript and compliant browsers.

/**
 * The copyright in this software is being made available under the BSD License,
 * included below. This software may be subject to other third party and contributor
 * rights, including patent rights, and no such rights are granted under this license.
 *
 * Copyright (c) 2013, Dash Industry Forum.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *  * Redistributions of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation and/or
 *  other materials provided with the distribution.
 *  * Neither the name of Dash Industry Forum nor the names of its
 *  contributors may be used to endorse or promote products derived from this software
 *  without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS AND ANY
 *  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 *  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 *  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 *  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

import FactoryMaker from '../../core/FactoryMaker';
import SwitchRequest from './SwitchRequest';

const SWITCH_REQUEST_HISTORY_DEPTH = 8; // must be > SwitchHistoryRule SAMPLE_SIZE to enable rule

function SwitchRequestHistory() {
    let switchRequests = []; // running total
    let srHistory = []; // history of each switch

    function push(switchRequest) {
        if (switchRequest.newValue === SwitchRequest.NO_CHANGE) {
            switchRequest.newValue = switchRequest.oldValue;
        }
        if (!switchRequests[switchRequest.oldValue]) {
            switchRequests[switchRequest.oldValue] = {noDrops: 0, drops: 0, dropSize: 0};
        }

        // Set switch details
        let indexDiff = switchRequest.newValue - switchRequest.oldValue;
        let drop = (indexDiff < 0) ? 1 : 0;
        let dropSize = drop ? -indexDiff : 0;
        let noDrop = drop ? 0 : 1;

        // Update running totals
        switchRequests[switchRequest.oldValue].drops += drop;
        switchRequests[switchRequest.oldValue].dropSize += dropSize;
        switchRequests[switchRequest.oldValue].noDrops += noDrop;

        // Save to history
        srHistory.push({idx: switchRequest.oldValue, noDrop: noDrop, drop: drop, dropSize: dropSize});

        // Shift earliest switch off srHistory and readjust to keep depth of running totals constant
        if ( srHistory.length > SWITCH_REQUEST_HISTORY_DEPTH ) {
            let srHistoryFirst = srHistory.shift();
            switchRequests[srHistoryFirst.idx].drops -= srHistoryFirst.drop;
            switchRequests[srHistoryFirst.idx].dropSize -= srHistoryFirst.dropSize;
            switchRequests[srHistoryFirst.idx].noDrops -= srHistoryFirst.noDrop;
        }
    }

    function getSwitchRequests() {
        return switchRequests;
    }

    function reset() {
        switchRequests = [];
        srHistory = [];
    }

    return {
        push: push,
        getSwitchRequests: getSwitchRequests,
        reset: reset
    };
}

SwitchRequestHistory.__dashjs_factory_name = 'SwitchRequestHistory';
const factory = FactoryMaker.getClassFactory(SwitchRequestHistory);
export default factory;