I've hacked up a solution! It requires only two files:
- The video file.
- The HTML file, containing:
- The subtitles in either VTT or SRT format.
- A script to parse the embedded VTT text and add it to the video.
Get my solution from this GitHub Gist, or from below:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Playing a local video</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
<style>
html, body {
background: black;
color: white;
}
html, body, video {
padding: 0;
margin: 0;
}
video {
position: absolute;
top: 0;
left: 0;
bottom: 0;
right: 0;
width: 100%;
height: 100%;
}
</style>
</head>
<body>
<video controls>
<source src="Your local video file.mp4" type="video/mp4">
</video>
<!-- Check https://quuz.org/webvtt/ for validation. -->
<script type="text/vtt" id="subtitle" data-label="English" data-lang="en">
WEBVTT
1
00:00:02.500 --> 00:00:05.250
Instead of loading an external .vtt file,
2
00:00:05.250 --> 00:00:09.750
The workaround is to embed it inside a script tag,
3
00:00:10.001 --> 00:00:15.000
And then parse it using JavaScript
and dynamically add it as a new TextTrack.
</script>
<script>
function parse_timestamp(s) {
var match = s.match(/^(?:([0-9]{2,}):)?([0-5][0-9]):([0-5][0-9][.,][0-9]{0,3})/);
if (match == null) {
throw 'Invalid timestamp format: ' + s;
}
var hours = parseInt(match[1] || "0", 10);
var minutes = parseInt(match[2], 10);
var seconds = parseFloat(match[3].replace(',', '.'));
return seconds + 60 * minutes + 60 * 60 * hours;
}
// https://w3c.github.io/webvtt/
// https://developer.mozilla.org/en/docs/Web/API/Web_Video_Text_Tracks_Format
// https://en.wikipedia.org/wiki/WebVTT
//
// For better parsers, look at:
// https://github.com/annevk/webvtt
// https://github.com/mozilla/vtt.js
function quick_and_dirty_vtt_or_srt_parser(vtt) {
var lines = vtt.trim().replace('\r\n', '\n').split(/[\r\n]/).map(function(line) {
return line.trim();
});
var cues = [];
var start = null;
var end = null;
var payload = null;
for (var i = 0; i < lines.length; i++) {
if (lines[i].indexOf('-->') >= 0) {
var splitted = lines[i].split(/[ \t]+-->[ \t]+/);
if (splitted.length != 2) {
throw 'Error when splitting "-->": ' + lines[i];
}
// Already ignoring anything past the "end" timestamp (i.e. cue settings).
start = parse_timestamp(splitted[0]);
end = parse_timestamp(splitted[1]);
} else if (lines[i] == '') {
if (start && end) {
var cue = new VTTCue(start, end, payload);
cues.push(cue);
start = null;
end = null;
payload = null;
}
} else if(start && end) {
if (payload == null) {
payload = lines[i];
} else {
payload += '\n' + lines[i];
}
}
}
return cues;
}
function init() {
// http://www.html5rocks.com/en/tutorials/track/basics/
// https://www.iandevlin.com/blog/2015/02/javascript/dynamically-adding-text-tracks-to-html5-video
var video = document.querySelector('video');
var subtitle = document.getElementById('subtitle');
var track = video.addTextTrack('subtitles', subtitle.dataset.label, subtitle.dataset.lang);
track.mode = "showing";
quick_and_dirty_vtt_or_srt_parser(subtitle.innerHTML).map(function(cue) {
track.addCue(cue);
});
}
init();
</script>
</body>
</html>
Alternative approaches:
