videojs-hls.js
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/*
* video-js-hls
*
*
* Copyright (c) 2013 Brightcove
* All rights reserved.
*/
(function(window, videojs, document, undefined) {
videojs.hls = {
/**
* Whether the browser has built-in HLS support.
*/
supportsNativeHls: (function() {
var
video = document.createElement('video'),
xMpegUrl,
vndMpeg;
// native HLS is definitely not supported if HTML5 video isn't
if (!videojs.Html5.isSupported()) {
return false;
}
xMpegUrl = video.canPlayType('application/x-mpegURL');
vndMpeg = video.canPlayType('application/vnd.apple.mpegURL');
return (/probably|maybe/).test(xMpegUrl) ||
(/probably|maybe/).test(vndMpeg);
})()
};
var
// the desired length of video to maintain in the buffer, in seconds
goalBufferLength = 5,
// a fudge factor to apply to advertised playlist bitrates to account for
// temporary flucations in client bandwidth
bandwidthVariance = 1.1,
/**
* A comparator function to sort two playlist object by bandwidth.
* @param left {object} a media playlist object
* @param right {object} a media playlist object
* @return {number} Greater than zero if the bandwidth attribute of
* left is greater than the corresponding attribute of right. Less
* than zero if the bandwidth of right is greater than left and
* exactly zero if the two are equal.
*/
playlistBandwidth = function(left, right) {
var leftBandwidth, rightBandwidth;
if (left.attributes && left.attributes.BANDWIDTH) {
leftBandwidth = left.attributes.BANDWIDTH;
}
leftBandwidth = leftBandwidth || window.Number.MAX_VALUE;
if (right.attributes && right.attributes.BANDWIDTH) {
rightBandwidth = right.attributes.BANDWIDTH;
}
rightBandwidth = rightBandwidth || window.Number.MAX_VALUE;
return leftBandwidth - rightBandwidth;
},
/**
* A comparator function to sort two playlist object by resolution (width).
* @param left {object} a media playlist object
* @param right {object} a media playlist object
* @return {number} Greater than zero if the resolution.width attribute of
* left is greater than the corresponding attribute of right. Less
* than zero if the resolution.width of right is greater than left and
* exactly zero if the two are equal.
*/
playlistResolution = function(left, right) {
var leftWidth, rightWidth;
if(left.attributes && left.attributes.RESOLUTION && left.attributes.RESOLUTION.width) {
leftWidth = left.attributes.RESOLUTION.width;
}
leftWidth = leftWidth || window.Number.MAX_VALUE;
if(right.attributes && right.attributes.RESOLUTION && right.attributes.RESOLUTION.width) {
rightWidth = right.attributes.RESOLUTION.width;
}
rightWidth = rightWidth || window.Number.MAX_VALUE;
return leftWidth - rightWidth;
},
/**
* TODO - Document this great feature.
*
* @param playlist
* @param time
* @returns int
*/
getMediaIndexByTime = function(playlist, time) {
var index, counter, timeRanges, currentSegmentRange;
timeRanges = [];
for (index = 0; index < playlist.segments.length; index++) {
currentSegmentRange = {};
currentSegmentRange.start = (index === 0) ? 0 : timeRanges[index - 1].end;
currentSegmentRange.end = currentSegmentRange.start + playlist.segments[index].duration;
timeRanges.push(currentSegmentRange);
}
for (counter = 0; counter < timeRanges.length; counter++) {
if (time >= timeRanges[counter].start && time < timeRanges[counter].end) {
return counter;
}
}
return -1;
},
/**
* Calculate the total duration for a playlist based on segment metadata.
* @param playlist {object} a media playlist object
* @return {number} the currently known duration, in seconds
*/
totalDuration = function(playlist) {
var
duration = 0,
i = playlist.segments.length,
segment;
while (i--) {
segment = playlist.segments[i];
duration += segment.duration || playlist.targetDuration || 0;
}
return duration;
},
/**
* Constructs a new URI by interpreting a path relative to another
* URI.
* @param basePath {string} a relative or absolute URI
* @param path {string} a path part to combine with the base
* @return {string} a URI that is equivalent to composing `base`
* with `path`
* @see http://stackoverflow.com/questions/470832/getting-an-absolute-url-from-a-relative-one-ie6-issue
*/
resolveUrl = function(basePath, path) {
// use the base element to get the browser to handle URI resolution
var
oldBase = document.querySelector('base'),
docHead = document.querySelector('head'),
a = document.createElement('a'),
base = oldBase,
oldHref,
result;
// prep the document
if (oldBase) {
oldHref = oldBase.href;
} else {
base = docHead.appendChild(document.createElement('base'));
}
base.href = basePath;
a.href = path;
result = a.href;
// clean up
if (oldBase) {
oldBase.href = oldHref;
} else {
docHead.removeChild(base);
}
return result;
},
/**
* Initializes the HLS plugin.
* @param options {mixed} the URL to an HLS playlist
*/
init = function(options) {
var
mediaSource = new videojs.MediaSource(),
segmentParser = new videojs.hls.SegmentParser(),
player = this,
currentSrc,
extname,
srcUrl,
segmentXhr,
downloadPlaylist,
fillBuffer;
// if the video element supports HLS natively, do nothing
if (videojs.hls.supportsNativeHls) {
return;
}
currentSrc = player.currentSrc();
// when the video element is initializing, currentSrc may be undefined
// grab the src from the video element because video.js doesn't currently
// expose it
if (!currentSrc) {
currentSrc = player.el().querySelector('.vjs-tech').src;
}
extname = (/[^#?]*(?:\/[^#?]*\.([^#?]*))/).exec(currentSrc);
if (typeof options === 'string') {
srcUrl = options;
} else if (options) {
srcUrl = options.url;
} else if (extname && extname[1] === 'm3u8') {
// if the currentSrc looks like an m3u8, attempt to use it
srcUrl = currentSrc;
} else {
// do nothing until the plugin is initialized with a valid URL
videojs.log('hls: no valid playlist URL specified');
return;
}
// expose the HLS plugin state
player.hls.readyState = function() {
if (!player.hls.media) {
return 0; // HAVE_NOTHING
}
return 1; // HAVE_METADATA
};
player.on('seeking', function() {
var currentTime = player.currentTime();
player.hls.mediaIndex = getMediaIndexByTime(player.hls.media, currentTime);
if (segmentXhr) {
segmentXhr.abort();
}
fillBuffer(currentTime * 1000);
});
player.hls.useViewportSelection = true;
/**
* Chooses the appropriate media playlist based on the current
* bandwidth estimate and the player size.
* @return the highest bitrate playlist less than the currently detected
* bandwidth, accounting for some amount of bandwidth variance
*/
player.hls.selectPlaylist = function() {
var
bestVariant,
effectiveBitrate,
sortedPlaylists = player.hls.master.playlists.slice(),
mappedPlaylists = [],
i = sortedPlaylists.length,
variant;
sortedPlaylists.sort(playlistBandwidth);
// determine best variant by bandwidth
while (i--) {
variant = sortedPlaylists[i];
// ignore playlists without bandwidth information
if (!variant.attributes || !variant.attributes.BANDWIDTH) {
continue;
}
effectiveBitrate = variant.attributes.BANDWIDTH * bandwidthVariance;
// since the playlists are sorted in ascending order by bandwidth, the
// current variant is the best as long as its effective bitrate is
// below the current bandwidth estimate
if (effectiveBitrate < player.hls.bandwidth) {
bestVariant = variant;
break;
}
}
// determine best variant by resolution
// we only want to run this if bandwidth routine above determined a best variant and override is true (default)
if (bestVariant && player.hls.useViewportSelection) {
// reset i
i = sortedPlaylists.length;
// map the playlists by resolution
// NOTE - this needs to be separate routine because eventually we want to set to index+1
while(i--) {
variant = sortedPlaylists[i];
// ignored playlists without resolution information
if (!variant.attributes || !variant.attributes.RESOLUTION || !variant.attributes.RESOLUTION.width || !variant.attributes.RESOLUTION.height) {
continue;
}
mappedPlaylists.push(variant);
}
// set index to the available mapped renditions
i = mappedPlaylists.length;
// sort by resolution [currently widths]
mappedPlaylists.sort(playlistResolution);
// iterate through the mapped playlists and assign a best variant based on rendition resolution
while (i--) {
variant = mappedPlaylists[i];
// override the bandwidth best variant with the best rendition variant
if (variant.attributes.RESOLUTION.width <= player.width() && variant.attributes.RESOLUTION.height <= player.height()) {
bestVariant = variant;
// TODO - select the variant one index higher than the best variant to account for dimension variance
/*
if( mappedPlaylists[i+1] != undefined )
{
bestVariant = mappedPlaylists[i+1];
*/
break;
}
}
}
// if no acceptable variant was found, fall back on the lowest
// bitrate playlist
return bestVariant || sortedPlaylists[0];
};
/**
* Download an M3U8 and update the current manifest object. If the provided
* URL is a master playlist, the default variant will be downloaded and
* parsed as well. Triggers `loadedmanifest` once for each playlist that is
* downloaded and `loadedmetadata` after at least one media playlist has
* been parsed. Whether multiple playlists were downloaded or not, when
* `loadedmetadata` fires a parsed or inferred master playlist object will
* be available as `player.hls.master`.
*
* @param url {string} a URL to the M3U8 file to process
*/
downloadPlaylist = function(url) {
var xhr = new window.XMLHttpRequest();
xhr.open('GET', url);
xhr.onreadystatechange = function() {
var i, parser, playlist, playlistUri;
if (xhr.readyState === 4) {
if (xhr.status >= 400 || this.status === 0) {
player.hls.error = {
status: xhr.status,
message: 'HLS playlist request error at URL: ' + url,
code: (xhr.status >= 500) ? 4 : 2
};
player.trigger('error');
return;
}
// readystate DONE
parser = new videojs.m3u8.Parser();
parser.push(xhr.responseText);
// master playlists
if (parser.manifest.playlists) {
player.hls.master = parser.manifest;
downloadPlaylist(resolveUrl(url, parser.manifest.playlists[0].uri));
player.trigger('loadedmanifest');
return;
}
// media playlists
if (player.hls.master) {
// merge this playlist into the master
i = player.hls.master.playlists.length;
while (i--) {
playlist = player.hls.master.playlists[i];
playlistUri = resolveUrl(srcUrl, playlist.uri);
if (playlistUri === url) {
player.hls.master.playlists[i] =
videojs.util.mergeOptions(playlist, parser.manifest);
}
}
} else {
// infer a master playlist if none was previously requested
player.hls.master = {
playlists: [parser.manifest]
};
}
// always start playback with the default rendition
if (!player.hls.media) {
player.hls.media = player.hls.master.playlists[0];
// update the duration
if (parser.manifest.totalDuration) {
player.duration(parser.manifest.totalDuration);
} else {
player.duration(totalDuration(parser.manifest));
}
// periodicaly check if the buffer needs to be refilled
player.on('timeupdate', fillBuffer);
player.trigger('loadedmanifest');
player.trigger('loadedmetadata');
fillBuffer();
return;
}
// select a playlist and download its metadata if necessary
playlist = player.hls.selectPlaylist();
if (!playlist.segments) {
downloadPlaylist(resolveUrl(srcUrl, playlist.uri));
} else {
player.hls.media = playlist;
// update the duration
if (player.hls.media.totalDuration) {
player.duration(player.hls.media.totalDuration);
} else {
player.duration(totalDuration(player.hls.media));
}
}
player.trigger('loadedmanifest');
}
};
xhr.send(null);
};
/**
* Determines whether there is enough video data currently in the buffer
* and downloads a new segment if the buffered time is less than the goal.
* @param offset (optional) {number} the offset into the downloaded segment
* to seek to, in milliseconds
*/
fillBuffer = function(offset) {
var
buffered = player.buffered(),
bufferedTime = 0,
segment = player.hls.media.segments[player.hls.mediaIndex],
segmentUri,
startTime;
// if there is a request already in flight, do nothing
if (segmentXhr) {
return;
}
// if the video has finished downloading, stop trying to buffer
if (!segment) {
return;
}
if (buffered) {
// assuming a single, contiguous buffer region
bufferedTime = player.buffered().end(0) - player.currentTime();
}
// if there is plenty of content in the buffer, relax for awhile
if (bufferedTime >= goalBufferLength) {
return;
}
segmentUri = resolveUrl(resolveUrl(srcUrl, player.hls.media.uri || ''),
segment.uri);
// request the next segment
segmentXhr = new window.XMLHttpRequest();
segmentXhr.open('GET', segmentUri);
segmentXhr.responseType = 'arraybuffer';
segmentXhr.onreadystatechange = function() {
var playlist;
// wait until the request completes
if (this.readyState !== 4) {
return;
}
// the segment request is no longer outstanding
segmentXhr = null;
// trigger an error if the request was not successful
if (this.status >= 400) {
player.hls.error = {
status: this.status,
message: 'HLS segment request error at URL: ' + segmentUri,
code: (this.status >= 500) ? 4 : 2
};
player.trigger('error');
return;
}
// stop processing if the request was aborted
if (!this.response) {
return;
}
// calculate the download bandwidth
player.hls.segmentXhrTime = (+new Date()) - startTime;
player.hls.bandwidth = (this.response.byteLength / player.hls.segmentXhrTime) * 8 * 1000;
// transmux the segment data from MP2T to FLV
segmentParser.parseSegmentBinaryData(new Uint8Array(this.response));
// if we're refilling the buffer after a seek, scan through the muxed
// FLV tags until we find the one that is closest to the desired
// playback time
if (offset !== undefined && typeof offset === "number") {
while (segmentParser.getTags()[0].pts < offset) {
// we're seeking past this tag, so ignore it
segmentParser.getNextTag();
}
}
while (segmentParser.tagsAvailable()) {
player.hls.sourceBuffer.appendBuffer(segmentParser.getNextTag().bytes, player);
}
player.hls.mediaIndex++;
if (player.hls.mediaIndex === player.hls.media.segments.length) {
mediaSource.endOfStream();
return;
}
// figure out what stream the next segment should be downloaded from
// with the updated bandwidth information
playlist = player.hls.selectPlaylist();
if (!playlist.segments) {
downloadPlaylist(resolveUrl(srcUrl, playlist.uri));
} else {
player.hls.media = playlist;
}
};
startTime = +new Date();
segmentXhr.send(null);
};
// load the MediaSource into the player
mediaSource.addEventListener('sourceopen', function() {
// construct the video data buffer and set the appropriate MIME type
var sourceBuffer = mediaSource.addSourceBuffer('video/flv; codecs="vp6,aac"');
player.hls.sourceBuffer = sourceBuffer;
sourceBuffer.appendBuffer(segmentParser.getFlvHeader());
player.hls.mediaIndex = 0;
downloadPlaylist(srcUrl);
});
player.src({
src: videojs.URL.createObjectURL(mediaSource),
type: "video/flv"
});
};
videojs.plugin('hls', function() {
var initialize = function() {
return function() {
this.hls = initialize();
init.apply(this, arguments);
};
};
initialize().apply(this, arguments);
});
})(window, window.videojs, document);