@l5i/dashjs/src/dash/utils/TimelineConverter.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 EventBus from '../../core/EventBus';
import Events from '../../core/events/Events';
import FactoryMaker from '../../core/FactoryMaker';

function TimelineConverter() {

    let context = this.context;
    let eventBus = EventBus(context).getInstance();

    let instance,
        clientServerTimeShift,
        isClientServerTimeSyncCompleted,
        expectedLiveEdge;

    function initialize() {
        resetInitialSettings();
        eventBus.on(Events.TIME_SYNCHRONIZATION_COMPLETED, onTimeSyncComplete, this);
    }

    function isTimeSyncCompleted() {
        return isClientServerTimeSyncCompleted;
    }

    function setTimeSyncCompleted(value) {
        isClientServerTimeSyncCompleted = value;
    }

    function getClientTimeOffset() {
        return clientServerTimeShift;
    }

    function setClientTimeOffset(value) {
        clientServerTimeShift = value;
    }

    function getExpectedLiveEdge() {
        return expectedLiveEdge;
    }

    function setExpectedLiveEdge(value) {
        expectedLiveEdge = value;
    }

    function calcAvailabilityTimeFromPresentationTime(presentationTime, mpd, isDynamic, calculateEnd) {
        let availabilityTime = NaN;

        if (calculateEnd) {
            //@timeShiftBufferDepth specifies the duration of the time shifting buffer that is guaranteed
            // to be available for a Media Presentation with type 'dynamic'.
            // When not present, the value is infinite.
            if (isDynamic && (mpd.timeShiftBufferDepth != Number.POSITIVE_INFINITY)) {
                availabilityTime = new Date(mpd.availabilityStartTime.getTime() + ((presentationTime + mpd.timeShiftBufferDepth) * 1000));
            } else {
                availabilityTime = mpd.availabilityEndTime;
            }
        } else {
            if (isDynamic) {
                availabilityTime = new Date(mpd.availabilityStartTime.getTime() + (presentationTime - clientServerTimeShift) * 1000);
            } else {
                // in static mpd, all segments are available at the same time
                availabilityTime = mpd.availabilityStartTime;
            }
        }

        return availabilityTime;
    }

    function calcAvailabilityStartTimeFromPresentationTime(presentationTime, mpd, isDynamic) {
        return calcAvailabilityTimeFromPresentationTime.call(this, presentationTime, mpd, isDynamic);
    }

    function calcAvailabilityEndTimeFromPresentationTime(presentationTime, mpd, isDynamic) {
        return calcAvailabilityTimeFromPresentationTime.call(this, presentationTime, mpd, isDynamic, true);
    }

    function calcPresentationTimeFromWallTime(wallTime, period) {
        return ((wallTime.getTime() - period.mpd.availabilityStartTime.getTime() + clientServerTimeShift * 1000) / 1000);
    }

    function calcPresentationTimeFromMediaTime(mediaTime, representation) {
        const periodStart = representation.adaptation.period.start;
        const presentationOffset = representation.presentationTimeOffset;

        return mediaTime + (periodStart - presentationOffset);
    }

    function calcMediaTimeFromPresentationTime(presentationTime, representation) {
        const periodStart = representation.adaptation.period.start;
        const presentationOffset = representation.presentationTimeOffset;

        return presentationTime - periodStart + presentationOffset;
    }

    function calcWallTimeForSegment(segment, isDynamic) {
        let suggestedPresentationDelay,
            displayStartTime,
            wallTime;

        if (isDynamic) {
            suggestedPresentationDelay = segment.representation.adaptation.period.mpd.suggestedPresentationDelay;
            displayStartTime = segment.presentationStartTime + suggestedPresentationDelay;
            wallTime = new Date(segment.availabilityStartTime.getTime() + (displayStartTime * 1000));
        }

        return wallTime;
    }

    function calcSegmentAvailabilityRange(voRepresentation, isDynamic) {
        // Static Range Finder
        const voPeriod = voRepresentation.adaptation.period;
        const range = { start: voPeriod.start, end: voPeriod.start + voPeriod.duration };
        if (!isDynamic) return range;

        if (!isClientServerTimeSyncCompleted && voRepresentation.segmentAvailabilityRange) {
            return voRepresentation.segmentAvailabilityRange;
        }

        // Dynamic Range Finder
        const d = voRepresentation.segmentDuration || (voRepresentation.segments && voRepresentation.segments.length ? voRepresentation.segments[voRepresentation.segments.length - 1].duration : 0);
        const now = calcPresentationTimeFromWallTime(new Date(), voPeriod);
        const periodEnd = voPeriod.start + voPeriod.duration;
        range.start = Math.max((now - voPeriod.mpd.timeShiftBufferDepth), voPeriod.start);

        const endOffset = voRepresentation.availabilityTimeOffset !== undefined &&
            voRepresentation.availabilityTimeOffset < d ? d - voRepresentation.availabilityTimeOffset : d;
        range.end = now >= periodEnd && now - endOffset < periodEnd ? periodEnd : now - endOffset;

        return range;
    }

    function calcPeriodRelativeTimeFromMpdRelativeTime(representation, mpdRelativeTime) {
        const periodStartTime = representation.adaptation.period.start;
        return mpdRelativeTime - periodStartTime;
    }

    /*
    * We need to figure out if we want to timesync for segmentTimeine where useCalculatedLiveEdge = true
    * seems we figure out client offset based on logic in liveEdgeFinder getLiveEdge timelineConverter.setClientTimeOffset(liveEdge - representationInfo.DVRWindow.end);
    * FYI StreamController's onManifestUpdated entry point to timeSync
    * */
    function onTimeSyncComplete(e) {

        if (isClientServerTimeSyncCompleted) return;

        if (e.offset !== undefined) {

            setClientTimeOffset(e.offset / 1000);
            isClientServerTimeSyncCompleted = true;

        }
    }

    function calcMSETimeOffset(representation) {
        // The MSEOffset is offset from AST for media. It is Period@start - presentationTimeOffset
        const presentationOffset = representation.presentationTimeOffset;
        const periodStart = representation.adaptation.period.start;
        return (periodStart - presentationOffset);
    }

    function resetInitialSettings() {
        clientServerTimeShift = 0;
        isClientServerTimeSyncCompleted = false;
        expectedLiveEdge = NaN;
    }

    function reset() {
        eventBus.off(Events.TIME_SYNCHRONIZATION_COMPLETED, onTimeSyncComplete, this);
        resetInitialSettings();
    }

    instance = {
        initialize: initialize,
        isTimeSyncCompleted: isTimeSyncCompleted,
        setTimeSyncCompleted: setTimeSyncCompleted,
        getClientTimeOffset: getClientTimeOffset,
        setClientTimeOffset: setClientTimeOffset,
        getExpectedLiveEdge: getExpectedLiveEdge,
        setExpectedLiveEdge: setExpectedLiveEdge,
        calcAvailabilityStartTimeFromPresentationTime: calcAvailabilityStartTimeFromPresentationTime,
        calcAvailabilityEndTimeFromPresentationTime: calcAvailabilityEndTimeFromPresentationTime,
        calcPresentationTimeFromWallTime: calcPresentationTimeFromWallTime,
        calcPresentationTimeFromMediaTime: calcPresentationTimeFromMediaTime,
        calcPeriodRelativeTimeFromMpdRelativeTime: calcPeriodRelativeTimeFromMpdRelativeTime,
        calcMediaTimeFromPresentationTime: calcMediaTimeFromPresentationTime,
        calcSegmentAvailabilityRange: calcSegmentAvailabilityRange,
        calcWallTimeForSegment: calcWallTimeForSegment,
        calcMSETimeOffset: calcMSETimeOffset,
        reset: reset
    };

    return instance;
}

TimelineConverter.__dashjs_factory_name = 'TimelineConverter';
export default FactoryMaker.getSingletonFactory(TimelineConverter);