metadata-stream.js
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/**
* Accepts program elementary stream (PES) data events and parses out
* ID3 metadata from them, if present.
* @see http://id3.org/id3v2.3.0
*/
(function(window, videojs, undefined) {
'use strict';
var
parseString = function(bytes, start, end) {
var i, result = '';
for (i = start; i < end; i++) {
result += '%' + ('00' + bytes[i].toString(16)).slice(-2);
}
return window.decodeURIComponent(result);
},
tagParsers = {
'TXXX': function(tag) {
var i;
if (tag.data[0] !== 3) {
// ignore frames with unrecognized character encodings
return;
}
for (i = 1; i < tag.data.length; i++) {
if (tag.data[i] === 0) {
// parse the text fields
tag.description = parseString(tag.data, 1, i);
tag.value = parseString(tag.data, i + 1, tag.data.length);
break;
}
}
},
'WXXX': function(tag) {
var i;
if (tag.data[0] !== 3) {
// ignore frames with unrecognized character encodings
return;
}
for (i = 1; i < tag.data.length; i++) {
if (tag.data[i] === 0) {
// parse the description and URL fields
tag.description = parseString(tag.data, 1, i);
tag.url = parseString(tag.data, i + 1, tag.data.length);
break;
}
}
}
},
MetadataStream;
MetadataStream = function(options) {
var settings = {
debug: !!(options && options.debug),
// the bytes of the program-level descriptor field in MP2T
// see ISO/IEC 13818-1:2013 (E), section 2.6 "Program and
// program element descriptors"
descriptor: options && options.descriptor
}, i;
MetadataStream.prototype.init.call(this);
// calculate the text track in-band metadata track dispatch type
// https://html.spec.whatwg.org/multipage/embedded-content.html#steps-to-expose-a-media-resource-specific-text-track
this.dispatchType = videojs.Hls.SegmentParser.STREAM_TYPES.metadata.toString(16);
if (settings.descriptor) {
for (i = 0; i < settings.descriptor.length; i++) {
this.dispatchType += ('00' + settings.descriptor[i].toString(16)).slice(-2);
}
}
this.push = function(chunk) {
var tagSize, frameStart, frameSize, frame;
// ignore events that don't look like ID3 data
if (chunk.data.length < 10 ||
chunk.data[0] !== 'I'.charCodeAt(0) ||
chunk.data[1] !== 'D'.charCodeAt(0) ||
chunk.data[2] !== '3'.charCodeAt(0)) {
if (settings.debug) {
videojs.log('Skipping unrecognized metadata stream');
}
return;
}
// find the start of the first frame and the end of the tag
tagSize = chunk.data.byteLength;
frameStart = 10;
if (chunk.data[5] & 0x40) {
// advance the frame start past the extended header
frameStart += 4; // header size field
frameStart += (chunk.data[10] << 24) |
(chunk.data[11] << 16) |
(chunk.data[12] << 8) |
(chunk.data[13]);
// clip any padding off the end
tagSize -= (chunk.data[16] << 24) |
(chunk.data[17] << 16) |
(chunk.data[18] << 8) |
(chunk.data[19]);
}
// adjust the PTS values to align with the video and audio
// streams
if (this.timestampOffset) {
chunk.pts -= this.timestampOffset;
chunk.dts -= this.timestampOffset;
}
// parse one or more ID3 frames
// http://id3.org/id3v2.3.0#ID3v2_frame_overview
chunk.frames = [];
do {
// determine the number of bytes in this frame
frameSize = (chunk.data[frameStart + 4] << 24) |
(chunk.data[frameStart + 5] << 16) |
(chunk.data[frameStart + 6] << 8) |
(chunk.data[frameStart + 7]);
if (frameSize < 1) {
return videojs.log('Malformed ID3 frame encountered. Skipping metadata parsing.');
}
frame = {
id: String.fromCharCode(chunk.data[frameStart]) +
String.fromCharCode(chunk.data[frameStart + 1]) +
String.fromCharCode(chunk.data[frameStart + 2]) +
String.fromCharCode(chunk.data[frameStart + 3]),
data: chunk.data.subarray(frameStart + 10, frameStart + frameSize + 10)
};
if (tagParsers[frame.id]) {
tagParsers[frame.id](frame);
}
chunk.frames.push(frame);
frameStart += 10; // advance past the frame header
frameStart += frameSize; // advance past the frame body
} while (frameStart < tagSize);
this.trigger('data', chunk);
};
};
MetadataStream.prototype = new videojs.Hls.Stream();
videojs.Hls.MetadataStream = MetadataStream;
})(window, window.videojs);