videojs-bitmapsub

A video.js plugin helps you displaying bitmap subtitle type as image, like vobsub (DVD) or pgssub (Bluray).
Test it on demo page.

Table of Contents

• How it works
  • JS & CSS
  • Setting up plugin
    • Plugin options and defaults values
  • Append metadata tracks
    • Examples
• What metadata track generated contains
• [WIP]
• Crédits & inspiration
• License

How it works

This plugin can't handle vobsub or pgssub file as-is, you need to generate individual bitmap subtitle image and pack it into large images files. A webvtt metadata track file is used, describing which and when image must be displayed with its cues.
With that description, plugin select corresponding image region from packed subtitles images and display at given time into your video.js player instance.
This repository provide all you need to:

• extract and pack subtitles images from vobsub or pgssub
• generate corresponding webvtt metadata file description
• plugin to handle generated metadata track

NOTE: No OCR (Optical Character Recognition) involved into this process. Again, bitmap subtitles are displayed as images, and they are packed into bigger files only to avoid HTTP traffic, but it's not mandatory.

Usage

Prepare your data

Generate subtitles images packs with corresponding script from tools/ folder.

DVD .vob and .idx files — tools/vobsubpack.php

For DVD subtitles, two files are needed, a .vob and a .idx. With tools/vobsubpack.php you can specify one of them, second one is automaticaly find if they have same base name, only extension differs, eg: vobsub.vob and vobsub.idx.
It's an ugly script wrapper arround sub2png executable. (Why in PHP ?)
This script depend on subp2png binary and bash shell or compatible.

$ ./vobsubpack.php -i tmp/sample_vobsub_file.sub -o web_folder/

$ ./vobsubpack.php -h
vobsubpack.php

 -c    Number of columns, default 4.
 -h    This help description.
 -i    Input vobsub file, .sub or .idx extension
 -l    Number of lines, default 64.
 -o    Output directory
 -v    Print program version.

Bluray pgssub — tools/pgssubpack.py

Relatively slow python script.
Be careful, with default row and column values, pack image can easily have a resolution of 4000 × 6500 pixels, so browser can take time to load it or completely refuse to load too large image. It's specialy visible on image transition, like loading the first subtitle or seeking through video stream.

$ ./pgssubpack.py /tmp/sample.fre.sup -t bitmap-subtitle/
1823 image saved.

$ ./pgssubpack.py -h

usage: pgssubpack.py [-h] [-c COLUMNS] [-d] [-r ROWS] [-l LIMIT] [-t TARGETDIRECTORY] filename

Read PGS (.sup) file and generate pack of subtitles images. You can optionnaly define number of rows and columns.

positional arguments:
  filename

options:
  -h, --help            show this help message and exit
  -c COLUMNS, --columns COLUMNS
                        number of columns within image pack, default: 4
  -d, --debug           temporary files are not remove
  -r ROWS, --rows ROWS  number of rows within image pack, default: 64
  -l LIMIT, --limit LIMIT
                        limit number of subtitle to be processed, for tests purposes
  -t TARGETDIRECTORY, --targetDirectory TARGETDIRECTORY
                        folder destination for files generated

Installation

Install videojs-bitmapsub via npm:

$ npm install @goatscrub/videojs-bitmapsub

Append JS & CSS

Append CSS and javascript into your document.

<link href="//path-plugin/dist/videojs-bitmapsub.min.css" rel="stylesheet" />
<script src="//path-plugin/dist/videojs-bitmapsub.js"></script>

Setting up plugin

Two video.js classical ways, at video.js player creation:

// On player creation
const player1 = videojs('sample', {
  plugins: {
    bitmapsub: { pathPrefix: '/images-subtitles/' }
  }
});

// Passing options directly to plugin
const player2 = videojs('sample');

player2.bitmapsub({ pathPrefix: '/images-subtitles/' });

Plugin options and defaults values

name	default	description
pathPrefix	'/bitmapsub/'	web path to your subtitles packed images files
labelPrefix	''	menu label prefix
labelSuffix	' ⋅BMP'	menu label suffix
name	bitmapsub	instance plugin name

Append metadata tracks

Bitmapsub plugin search for metadata tracks and filters them by specific label prefix. Label prefix is composed of subtitle_type follow by video_size, separated by colon.
So to be recognized correctly, your label must match format: subtitle_type:video_width:track_label, with subtitle type defined as follow:

type	example	description
vobsub	label="vobsub:720:english"	DVD source with video image width 720px and label text english
pgssub	label="pgssub:1920:français"	Bluray source with video image width 1920px and label text français

Examples

<!-- DVD -->
<track kind="metadata" label="pgssub:1920:english" language="eng" src="/webvtt-path/file.eng.vtt" />

<!-- Bluray -->
<track kind="metadata" label="pgssub:1920:français" language="fre" src="/webvtt-path/file.fre.vtt" />

What metadata track generated contains

WEBVTT - sample_file.sub

NOTE Video size: 720x576
NOTE File generated with vobsubpack.php 2024-09-05 07:09:37
NOTE Cue format: bitmap-file.png:width:height:driftX:driftY

1
00:00:49.760 --> 00:00:51.239
sample_file.1.vobsub.png 73:22:0:0

[...]

[WIP]

• settings panel
• image pre-load
• moving packing script to RUST and handle both pgssub or vobsub
• append bitmap subtitles into subscapsmenu
• menu icon ?

Crédits & inspiration

• Presentation Graphic Stream (SUP files) BluRay Subtitle Format — Scorpius
• EzraBC / pgsreader — github
• robjtede / sup-decode — github
• DVD-Video Information
• yzi2004 / SupSubtitleParser — github
• patent: Method for RLE of a bitmap data stream
• mpeg program stream — wikipedia
• packetized elementary stream — wikipedia

License

MIT. Copyright (c) goatscrub Ludovic Mabilat