buymymojo.net/node_modules/@videojs/http-streaming/src/playlist.js
2021-07-02 19:29:34 +10:00

730 lines
22 KiB
JavaScript

/**
* @file playlist.js
*
* Playlist related utilities.
*/
import videojs from 'video.js';
import window from 'global/window';
import {isAudioCodec} from '@videojs/vhs-utils/es/codecs.js';
import {TIME_FUDGE_FACTOR} from './ranges.js';
const {createTimeRange} = videojs;
/**
* A function to get a combined list of parts and segments with durations
* and indexes.
*
* @param {Playlist} playlist the playlist to get the list for.
*
* @return {Array} The part/segment list.
*/
export const getPartsAndSegments = (playlist) => (playlist.segments || []).reduce((acc, segment, si) => {
if (segment.parts) {
segment.parts.forEach(function(part, pi) {
acc.push({duration: part.duration, segmentIndex: si, partIndex: pi, part, segment});
});
} else {
acc.push({duration: segment.duration, segmentIndex: si, partIndex: null, segment, part: null});
}
return acc;
}, []);
export const getLastParts = (media) => {
const lastSegment = media.segments && media.segments.length && media.segments[media.segments.length - 1];
return lastSegment && lastSegment.parts || [];
};
export const getKnownPartCount = ({preloadSegment}) => {
if (!preloadSegment) {
return;
}
const {parts, preloadHints} = preloadSegment;
let partCount = (preloadHints || [])
.reduce((count, hint) => count + (hint.type === 'PART' ? 1 : 0), 0);
partCount += (parts && parts.length) ? parts.length : 0;
return partCount;
};
/**
* Get the number of seconds to delay from the end of a
* live playlist.
*
* @param {Playlist} master the master playlist
* @param {Playlist} media the media playlist
* @return {number} the hold back in seconds.
*/
export const liveEdgeDelay = (master, media) => {
if (media.endList) {
return 0;
}
// dash suggestedPresentationDelay trumps everything
if (master && master.suggestedPresentationDelay) {
return master.suggestedPresentationDelay;
}
const hasParts = getLastParts(media).length > 0;
// look for "part" delays from ll-hls first
if (hasParts && media.serverControl && media.serverControl.partHoldBack) {
return media.serverControl.partHoldBack;
} else if (hasParts && media.partTargetDuration) {
return media.partTargetDuration * 3;
// finally look for full segment delays
} else if (media.serverControl && media.serverControl.holdBack) {
return media.serverControl.holdBack;
} else if (media.targetDuration) {
return media.targetDuration * 3;
}
return 0;
};
/**
* walk backward until we find a duration we can use
* or return a failure
*
* @param {Playlist} playlist the playlist to walk through
* @param {Number} endSequence the mediaSequence to stop walking on
*/
const backwardDuration = function(playlist, endSequence) {
let result = 0;
let i = endSequence - playlist.mediaSequence;
// if a start time is available for segment immediately following
// the interval, use it
let segment = playlist.segments[i];
// Walk backward until we find the latest segment with timeline
// information that is earlier than endSequence
if (segment) {
if (typeof segment.start !== 'undefined') {
return { result: segment.start, precise: true };
}
if (typeof segment.end !== 'undefined') {
return {
result: segment.end - segment.duration,
precise: true
};
}
}
while (i--) {
segment = playlist.segments[i];
if (typeof segment.end !== 'undefined') {
return { result: result + segment.end, precise: true };
}
result += segment.duration;
if (typeof segment.start !== 'undefined') {
return { result: result + segment.start, precise: true };
}
}
return { result, precise: false };
};
/**
* walk forward until we find a duration we can use
* or return a failure
*
* @param {Playlist} playlist the playlist to walk through
* @param {number} endSequence the mediaSequence to stop walking on
*/
const forwardDuration = function(playlist, endSequence) {
let result = 0;
let segment;
let i = endSequence - playlist.mediaSequence;
// Walk forward until we find the earliest segment with timeline
// information
for (; i < playlist.segments.length; i++) {
segment = playlist.segments[i];
if (typeof segment.start !== 'undefined') {
return {
result: segment.start - result,
precise: true
};
}
result += segment.duration;
if (typeof segment.end !== 'undefined') {
return {
result: segment.end - result,
precise: true
};
}
}
// indicate we didn't find a useful duration estimate
return { result: -1, precise: false };
};
/**
* Calculate the media duration from the segments associated with a
* playlist. The duration of a subinterval of the available segments
* may be calculated by specifying an end index.
*
* @param {Object} playlist a media playlist object
* @param {number=} endSequence an exclusive upper boundary
* for the playlist. Defaults to playlist length.
* @param {number} expired the amount of time that has dropped
* off the front of the playlist in a live scenario
* @return {number} the duration between the first available segment
* and end index.
*/
const intervalDuration = function(playlist, endSequence, expired) {
if (typeof endSequence === 'undefined') {
endSequence = playlist.mediaSequence + playlist.segments.length;
}
if (endSequence < playlist.mediaSequence) {
return 0;
}
// do a backward walk to estimate the duration
const backward = backwardDuration(playlist, endSequence);
if (backward.precise) {
// if we were able to base our duration estimate on timing
// information provided directly from the Media Source, return
// it
return backward.result;
}
// walk forward to see if a precise duration estimate can be made
// that way
const forward = forwardDuration(playlist, endSequence);
if (forward.precise) {
// we found a segment that has been buffered and so it's
// position is known precisely
return forward.result;
}
// return the less-precise, playlist-based duration estimate
return backward.result + expired;
};
/**
* Calculates the duration of a playlist. If a start and end index
* are specified, the duration will be for the subset of the media
* timeline between those two indices. The total duration for live
* playlists is always Infinity.
*
* @param {Object} playlist a media playlist object
* @param {number=} endSequence an exclusive upper
* boundary for the playlist. Defaults to the playlist media
* sequence number plus its length.
* @param {number=} expired the amount of time that has
* dropped off the front of the playlist in a live scenario
* @return {number} the duration between the start index and end
* index.
*/
export const duration = function(playlist, endSequence, expired) {
if (!playlist) {
return 0;
}
if (typeof expired !== 'number') {
expired = 0;
}
// if a slice of the total duration is not requested, use
// playlist-level duration indicators when they're present
if (typeof endSequence === 'undefined') {
// if present, use the duration specified in the playlist
if (playlist.totalDuration) {
return playlist.totalDuration;
}
// duration should be Infinity for live playlists
if (!playlist.endList) {
return window.Infinity;
}
}
// calculate the total duration based on the segment durations
return intervalDuration(
playlist,
endSequence,
expired
);
};
/**
* Calculate the time between two indexes in the current playlist
* neight the start- nor the end-index need to be within the current
* playlist in which case, the targetDuration of the playlist is used
* to approximate the durations of the segments
*
* @param {Array} options.durationList list to iterate over for durations.
* @param {number} options.defaultDuration duration to use for elements before or after the durationList
* @param {number} options.startIndex partsAndSegments index to start
* @param {number} options.endIndex partsAndSegments index to end.
* @return {number} the number of seconds between startIndex and endIndex
*/
export const sumDurations = function({defaultDuration, durationList, startIndex, endIndex}) {
let durations = 0;
if (startIndex > endIndex) {
[startIndex, endIndex] = [endIndex, startIndex];
}
if (startIndex < 0) {
for (let i = startIndex; i < Math.min(0, endIndex); i++) {
durations += defaultDuration;
}
startIndex = 0;
}
for (let i = startIndex; i < endIndex; i++) {
durations += durationList[i].duration;
}
return durations;
};
/**
* Calculates the playlist end time
*
* @param {Object} playlist a media playlist object
* @param {number=} expired the amount of time that has
* dropped off the front of the playlist in a live scenario
* @param {boolean|false} useSafeLiveEnd a boolean value indicating whether or not the
* playlist end calculation should consider the safe live end
* (truncate the playlist end by three segments). This is normally
* used for calculating the end of the playlist's seekable range.
* This takes into account the value of liveEdgePadding.
* Setting liveEdgePadding to 0 is equivalent to setting this to false.
* @param {number} liveEdgePadding a number indicating how far from the end of the playlist we should be in seconds.
* If this is provided, it is used in the safe live end calculation.
* Setting useSafeLiveEnd=false or liveEdgePadding=0 are equivalent.
* Corresponds to suggestedPresentationDelay in DASH manifests.
* @return {number} the end time of playlist
* @function playlistEnd
*/
export const playlistEnd = function(playlist, expired, useSafeLiveEnd, liveEdgePadding) {
if (!playlist || !playlist.segments) {
return null;
}
if (playlist.endList) {
return duration(playlist);
}
if (expired === null) {
return null;
}
expired = expired || 0;
let lastSegmentTime = intervalDuration(
playlist,
playlist.mediaSequence + playlist.segments.length,
expired
);
if (useSafeLiveEnd) {
liveEdgePadding = typeof liveEdgePadding === 'number' ? liveEdgePadding : liveEdgeDelay(null, playlist);
lastSegmentTime -= liveEdgePadding;
}
// don't return a time less than zero
return Math.max(0, lastSegmentTime);
};
/**
* Calculates the interval of time that is currently seekable in a
* playlist. The returned time ranges are relative to the earliest
* moment in the specified playlist that is still available. A full
* seekable implementation for live streams would need to offset
* these values by the duration of content that has expired from the
* stream.
*
* @param {Object} playlist a media playlist object
* dropped off the front of the playlist in a live scenario
* @param {number=} expired the amount of time that has
* dropped off the front of the playlist in a live scenario
* @param {number} liveEdgePadding how far from the end of the playlist we should be in seconds.
* Corresponds to suggestedPresentationDelay in DASH manifests.
* @return {TimeRanges} the periods of time that are valid targets
* for seeking
*/
export const seekable = function(playlist, expired, liveEdgePadding) {
const useSafeLiveEnd = true;
const seekableStart = expired || 0;
const seekableEnd = playlistEnd(playlist, expired, useSafeLiveEnd, liveEdgePadding);
if (seekableEnd === null) {
return createTimeRange();
}
return createTimeRange(seekableStart, seekableEnd);
};
/**
* Determine the index and estimated starting time of the segment that
* contains a specified playback position in a media playlist.
*
* @param {Object} options.playlist the media playlist to query
* @param {number} options.currentTime The number of seconds since the earliest
* possible position to determine the containing segment for
* @param {number} options.startTime the time when the segment/part starts
* @param {number} options.startingSegmentIndex the segment index to start looking at.
* @param {number?} [options.startingPartIndex] the part index to look at within the segment.
*
* @return {Object} an object with partIndex, segmentIndex, and startTime.
*/
export const getMediaInfoForTime = function({
playlist,
currentTime,
startingSegmentIndex,
startingPartIndex,
startTime
}) {
let time = currentTime - startTime;
const partsAndSegments = getPartsAndSegments(playlist);
let startIndex = 0;
for (let i = 0; i < partsAndSegments.length; i++) {
const partAndSegment = partsAndSegments[i];
if (startingSegmentIndex !== partAndSegment.segmentIndex) {
continue;
}
// skip this if part index does not match.
if (typeof startingPartIndex === 'number' && typeof partAndSegment.partIndex === 'number' && startingPartIndex !== partAndSegment.partIndex) {
continue;
}
startIndex = i;
break;
}
if (time < 0) {
// Walk backward from startIndex in the playlist, adding durations
// until we find a segment that contains `time` and return it
if (startIndex > 0) {
for (let i = startIndex - 1; i >= 0; i--) {
const partAndSegment = partsAndSegments[i];
time += partAndSegment.duration;
// TODO: consider not using TIME_FUDGE_FACTOR at all here
if ((time + TIME_FUDGE_FACTOR) > 0) {
return {
partIndex: partAndSegment.partIndex,
segmentIndex: partAndSegment.segmentIndex,
startTime: startTime - sumDurations({
defaultDuration: playlist.targetDuration,
durationList: partsAndSegments,
startIndex,
endIndex: i
})
};
}
}
}
// We were unable to find a good segment within the playlist
// so select the first segment
return {
partIndex: partsAndSegments[0] && partsAndSegments[0].partIndex || null,
segmentIndex: partsAndSegments[0] && partsAndSegments[0].segmentIndex || 0,
startTime: currentTime
};
}
// When startIndex is negative, we first walk forward to first segment
// adding target durations. If we "run out of time" before getting to
// the first segment, return the first segment
if (startIndex < 0) {
for (let i = startIndex; i < 0; i++) {
time -= playlist.targetDuration;
if (time < 0) {
return {
partIndex: partsAndSegments[0] && partsAndSegments[0].partIndex || null,
segmentIndex: partsAndSegments[0] && partsAndSegments[0].segmentIndex || 0,
startTime: currentTime
};
}
}
startIndex = 0;
}
// Walk forward from startIndex in the playlist, subtracting durations
// until we find a segment that contains `time` and return it
for (let i = startIndex; i < partsAndSegments.length; i++) {
const partAndSegment = partsAndSegments[i];
time -= partAndSegment.duration;
// TODO: consider not using TIME_FUDGE_FACTOR at all here
if ((time - TIME_FUDGE_FACTOR) < 0) {
return {
partIndex: partAndSegment.partIndex,
segmentIndex: partAndSegment.segmentIndex,
startTime: startTime + sumDurations({
defaultDuration: playlist.targetDuration,
durationList: partsAndSegments,
startIndex,
endIndex: i
})
};
}
}
// We are out of possible candidates so load the last one...
return {
segmentIndex: partsAndSegments[partsAndSegments.length - 1].segmentIndex,
partIndex: partsAndSegments[partsAndSegments.length - 1].partIndex,
startTime: currentTime
};
};
/**
* Check whether the playlist is blacklisted or not.
*
* @param {Object} playlist the media playlist object
* @return {boolean} whether the playlist is blacklisted or not
* @function isBlacklisted
*/
export const isBlacklisted = function(playlist) {
return playlist.excludeUntil && playlist.excludeUntil > Date.now();
};
/**
* Check whether the playlist is compatible with current playback configuration or has
* been blacklisted permanently for being incompatible.
*
* @param {Object} playlist the media playlist object
* @return {boolean} whether the playlist is incompatible or not
* @function isIncompatible
*/
export const isIncompatible = function(playlist) {
return playlist.excludeUntil && playlist.excludeUntil === Infinity;
};
/**
* Check whether the playlist is enabled or not.
*
* @param {Object} playlist the media playlist object
* @return {boolean} whether the playlist is enabled or not
* @function isEnabled
*/
export const isEnabled = function(playlist) {
const blacklisted = isBlacklisted(playlist);
return (!playlist.disabled && !blacklisted);
};
/**
* Check whether the playlist has been manually disabled through the representations api.
*
* @param {Object} playlist the media playlist object
* @return {boolean} whether the playlist is disabled manually or not
* @function isDisabled
*/
export const isDisabled = function(playlist) {
return playlist.disabled;
};
/**
* Returns whether the current playlist is an AES encrypted HLS stream
*
* @return {boolean} true if it's an AES encrypted HLS stream
*/
export const isAes = function(media) {
for (let i = 0; i < media.segments.length; i++) {
if (media.segments[i].key) {
return true;
}
}
return false;
};
/**
* Checks if the playlist has a value for the specified attribute
*
* @param {string} attr
* Attribute to check for
* @param {Object} playlist
* The media playlist object
* @return {boolean}
* Whether the playlist contains a value for the attribute or not
* @function hasAttribute
*/
export const hasAttribute = function(attr, playlist) {
return playlist.attributes && playlist.attributes[attr];
};
/**
* Estimates the time required to complete a segment download from the specified playlist
*
* @param {number} segmentDuration
* Duration of requested segment
* @param {number} bandwidth
* Current measured bandwidth of the player
* @param {Object} playlist
* The media playlist object
* @param {number=} bytesReceived
* Number of bytes already received for the request. Defaults to 0
* @return {number|NaN}
* The estimated time to request the segment. NaN if bandwidth information for
* the given playlist is unavailable
* @function estimateSegmentRequestTime
*/
export const estimateSegmentRequestTime = function(
segmentDuration,
bandwidth,
playlist,
bytesReceived = 0
) {
if (!hasAttribute('BANDWIDTH', playlist)) {
return NaN;
}
const size = segmentDuration * playlist.attributes.BANDWIDTH;
return (size - (bytesReceived * 8)) / bandwidth;
};
/*
* Returns whether the current playlist is the lowest rendition
*
* @return {Boolean} true if on lowest rendition
*/
export const isLowestEnabledRendition = (master, media) => {
if (master.playlists.length === 1) {
return true;
}
const currentBandwidth = media.attributes.BANDWIDTH || Number.MAX_VALUE;
return (master.playlists.filter((playlist) => {
if (!isEnabled(playlist)) {
return false;
}
return (playlist.attributes.BANDWIDTH || 0) < currentBandwidth;
}).length === 0);
};
export const playlistMatch = (a, b) => {
// both playlits are null
// or only one playlist is non-null
// no match
if (!a && !b || (!a && b) || (a && !b)) {
return false;
}
// playlist objects are the same, match
if (a === b) {
return true;
}
// first try to use id as it should be the most
// accurate
if (a.id && b.id && a.id === b.id) {
return true;
}
// next try to use reslovedUri as it should be the
// second most accurate.
if (a.resolvedUri && b.resolvedUri && a.resolvedUri === b.resolvedUri) {
return true;
}
// finally try to use uri as it should be accurate
// but might miss a few cases for relative uris
if (a.uri && b.uri && a.uri === b.uri) {
return true;
}
return false;
};
const someAudioVariant = function(master, callback) {
const AUDIO = master && master.mediaGroups && master.mediaGroups.AUDIO || {};
let found = false;
for (const groupName in AUDIO) {
for (const label in AUDIO[groupName]) {
found = callback(AUDIO[groupName][label]);
if (found) {
break;
}
}
if (found) {
break;
}
}
return !!found;
};
export const isAudioOnly = (master) => {
// we are audio only if we have no main playlists but do
// have media group playlists.
if (!master || !master.playlists || !master.playlists.length) {
// without audio variants or playlists this
// is not an audio only master.
const found = someAudioVariant(master, (variant) =>
(variant.playlists && variant.playlists.length) || variant.uri);
return found;
}
// if every playlist has only an audio codec it is audio only
for (let i = 0; i < master.playlists.length; i++) {
const playlist = master.playlists[i];
const CODECS = playlist.attributes && playlist.attributes.CODECS;
// all codecs are audio, this is an audio playlist.
if (CODECS && CODECS.split(',').every((c) => isAudioCodec(c))) {
continue;
}
// playlist is in an audio group it is audio only
const found = someAudioVariant(master, (variant) => playlistMatch(playlist, variant));
if (found) {
continue;
}
// if we make it here this playlist isn't audio and we
// are not audio only
return false;
}
// if we make it past every playlist without returning, then
// this is an audio only playlist.
return true;
};
// exports
export default {
liveEdgeDelay,
duration,
seekable,
getMediaInfoForTime,
isEnabled,
isDisabled,
isBlacklisted,
isIncompatible,
playlistEnd,
isAes,
hasAttribute,
estimateSegmentRequestTime,
isLowestEnabledRendition,
isAudioOnly,
playlistMatch
};