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1dc8dc12 by David LaPalomento
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Buffer ID3 tags split across TS packets 

If the entire ID3 frame isn't available in a single metadatastream push, store everything up and check with the combined data next time. Ignore tags that do not include at least the tag header in the first TS packet.
1 parent 3bf53170
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Showing 2 changed files with 172 additions and 43 deletions
......@@ -6,23 +6,24 @@
(function(window, videojs, undefined) {
'use strict';
var
// return the string representation of the specified byte range,
// interpreted as UTf-8.
parseUtf8 = function(bytes, start, end) {
// return a percent-encoded representation of the specified byte range
// @see http://en.wikipedia.org/wiki/Percent-encoding
percentEncode = 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);
return result;
},
// return the string representation of the specified byte range,
// interpreted as UTf-8.
parseUtf8 = function(bytes, start, end) {
return window.decodeURIComponent(percentEncode(bytes, start, end));
},
// return the string representation of the specified byte range,
// interpreted as ISO-8859-1.
parseIso88591 = function(bytes, start, end) {
var i, result = '';
for (i = start; i < end; i++) {
result += '%' + ('00' + bytes[i].toString(16)).slice(-2);
}
return window.unescape(result);
return window.unescape(percentEncode(bytes, start, end));
},
tagParsers = {
'TXXX': function(tag) {
......@@ -73,14 +74,23 @@
MetadataStream;
MetadataStream = function(options) {
var settings = {
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;
},
// the total size in bytes of the ID3 tag being parsed
tagSize = 0,
// tag data that is not complete enough to be parsed
buffer = [],
// the total number of bytes currently in the buffer
bufferSize = 0,
i;
MetadataStream.prototype.init.call(this);
// calculate the text track in-band metadata track dispatch type
......@@ -93,73 +103,110 @@
}
this.push = function(chunk) {
var tagSize, frameStart, frameSize, frame;
var tag, frameStart, frameSize, frame, i;
// ignore events that don't look like ID3 data
if (chunk.data.length < 10 ||
if (buffer.length === 0 &&
(chunk.data.length < 10 ||
chunk.data[0] !== 'I'.charCodeAt(0) ||
chunk.data[1] !== 'D'.charCodeAt(0) ||
chunk.data[2] !== '3'.charCodeAt(0)) {
chunk.data[2] !== '3'.charCodeAt(0))) {
if (settings.debug) {
videojs.log('Skipping unrecognized metadata stream');
videojs.log('Skipping unrecognized metadata packet');
}
return;
}
// add this chunk to the data we've collected so far
buffer.push(chunk);
bufferSize += chunk.data.byteLength;
// grab the size of the entire frame from the ID3 header
if (buffer.length === 1) {
// the frame size is transmitted as a 28-bit integer in the
// last four bytes of the ID3 header.
// The most significant bit of each byte is dropped and the
// results concatenated to recover the actual value.
tagSize = (chunk.data[6] << 21) |
(chunk.data[7] << 14) |
(chunk.data[8] << 7) |
(chunk.data[9]);
// ID3 reports the tag size excluding the header but it's more
// convenient for our comparisons to include it
tagSize += 10;
}
// if the entire frame has not arrived, wait for more data
if (bufferSize < tagSize) {
return;
}
// collect the entire frame so it can be parsed
tag = {
data: new Uint8Array(tagSize),
frames: [],
pts: buffer[0].pts,
dts: buffer[0].dts
};
for (i = 0; i < tagSize;) {
tag.data.set(buffer[0].data, i);
i += buffer[0].data.byteLength;
buffer.shift();
}
// find the start of the first frame and the end of the tag
tagSize = chunk.data.byteLength;
frameStart = 10;
if (chunk.data[5] & 0x40) {
if (tag.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]);
frameStart += (tag.data[10] << 24) |
(tag.data[11] << 16) |
(tag.data[12] << 8) |
(tag.data[13]);
// clip any padding off the end
tagSize -= (chunk.data[16] << 24) |
(chunk.data[17] << 16) |
(chunk.data[18] << 8) |
(chunk.data[19]);
tagSize -= (tag.data[16] << 24) |
(tag.data[17] << 16) |
(tag.data[18] << 8) |
(tag.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;
tag.pts -= this.timestampOffset;
tag.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]);
frameSize = (tag.data[frameStart + 4] << 24) |
(tag.data[frameStart + 5] << 16) |
(tag.data[frameStart + 6] << 8) |
(tag.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)
id: String.fromCharCode(tag.data[frameStart],
tag.data[frameStart + 1],
tag.data[frameStart + 2],
tag.data[frameStart + 3]),
data: tag.data.subarray(frameStart + 10, frameStart + frameSize + 10)
};
if (tagParsers[frame.id]) {
tagParsers[frame.id](frame);
}
chunk.frames.push(frame);
tag.frames.push(frame);
frameStart += 10; // advance past the frame header
frameStart += frameSize; // advance past the frame body
} while (frameStart < tagSize);
this.trigger('data', chunk);
this.trigger('data', tag);
};
};
MetadataStream.prototype = new videojs.Hls.Stream();
......
......@@ -206,7 +206,7 @@
equal(events[0].dts, 100, 'translated dts');
});
test('parses TXXX tags', function() {
test('parses TXXX frames', function() {
var events = [];
metadataStream.on('data', function(event) {
events.push(event);
......@@ -232,7 +232,7 @@
equal(events[0].frames[0].value, '{ "key": "value" }', 'parsed the value');
});
test('parses WXXX tags', function() {
test('parses WXXX frames', function() {
var events = [], url = 'http://example.com/path/file?abc=7&d=4#ty';
metadataStream.on('data', function(event) {
events.push(event);
......@@ -258,7 +258,7 @@
equal(events[0].frames[0].url, url, 'parsed the value');
});
test('parses TXXX tags with characters that have a single-digit hexadecimal representation', function() {
test('parses TXXX frames with characters that have a single-digit hexadecimal representation', function() {
var events = [], value = String.fromCharCode(7);
metadataStream.on('data', function(event) {
events.push(event);
......@@ -282,7 +282,7 @@
'parsed the single-digit character');
});
test('parses PRIV tags', function() {
test('parses PRIV frames', function() {
var
events = [],
payload = stringToInts('arbitrary data may be included in the payload ' +
......@@ -313,6 +313,88 @@
});
test('parses tags split across pushes', function() {
var
events = [],
owner = stringToCString('owner@example.com'),
payload = stringToInts('A TS packet is 188 bytes in length so that it can' +
' be easily transmitted over ATM networks, an ' +
'important medium at one time. We want to be sure' +
' that ID3 frames larger than a TS packet are ' +
'properly re-assembled.'),
tag = new Uint8Array(id3Tag(id3Frame('PRIV', owner, payload))),
front = tag.subarray(0, 100),
back = tag.subarray(100);
metadataStream.on('data', function(event) {
events.push(event);
});
metadataStream.push({
trackId: 7,
pts: 1000,
dts: 900,
data: front
});
equal(events.length, 0, 'parsed zero tags');
metadataStream.push({
trackId: 7,
pts: 1000,
dts: 900,
data: back
});
equal(events.length, 1, 'parsed a tag');
equal(events[0].frames.length, 1, 'parsed a frame');
equal(events[0].frames[0].data.byteLength,
owner.length + payload.length,
'collected data across pushes');
});
test('ignores tags when the header is fragmented', function() {
var
events = [],
tag = new Uint8Array(id3Tag(id3Frame('PRIV',
stringToCString('owner@example.com'),
stringToInts('payload')))),
// split the 10-byte ID3 tag header in half
front = tag.subarray(0, 5),
back = tag.subarray(5);
metadataStream.on('data', function(event) {
events.push(event);
});
metadataStream.push({
trackId: 7,
pts: 1000,
dts: 900,
data: front
});
metadataStream.push({
trackId: 7,
pts: 1000,
dts: 900,
data: back
});
equal(events.length, 0, 'parsed zero tags');
metadataStream.push({
trackId: 7,
pts: 1500,
dts: 1500,
data: new Uint8Array(id3Tag(id3Frame('PRIV',
stringToCString('owner2'),
stringToInts('payload2'))))
});
equal(events.length, 1, 'parsed one tag');
equal(events[0].frames[0].owner, 'owner2', 'dropped the first tag');
});
// https://html.spec.whatwg.org/multipage/embedded-content.html#steps-to-expose-a-media-resource-specific-text-track
test('constructs the dispatch type', function() {
metadataStream = new videojs.Hls.MetadataStream({
......