Subtitle SSA

1. Introduction
2. Setup
3. Functions
4. Subtitle Object
5. Concessions

Introduction

A pretty straightforward module for parsing and writing SSA/ASS/Aegisub/SubStation Alpha files which has been designed to closely resemble the two most popular SRT modules I could find, subtitles-parser and subtitle, following the latter's format slightly closer due to it using milleseconds by default in its object time properites.

This is part of a series of subtitle related modules which I will be publishing over the next while and have been scoped out in an earlier project on my github. As they were all originally part of a bigger project, there are doubtlessly some weird overlaps that need to be ironed out.

Written in ES5 purely because I thought it'd be a good restriction to put on myself (I won't be doing that again).

Setup

Dependencies: None!

• npm run build compiles a minified bundle file to use in the /dist folder, last I checked it was 3.3kb, which seems pretty good!
• npm run test tests code and assesses coverage
• npm run lint fairly simple ES5 lint checks on both source code and test files

Exported Functions

parse(data: String, [omitInlineStyles]) -> Array

Converts an SSA formatted string into a simple array of objects.

omitInlineStyles The optional second argument, which defaults to false, removes any inline styling provided in the subtitle file's dialogue field.

  var SSA = require('subtitle-ssa');
  var subFile = readFileFunction('./test/dummySubs/inlineStyle.ssa'); // check directory in repo

  SSA.parse(subFile);
  // RETURNS
  // [
  //   {
  //     start: 47100,
  //     end: 49100,
  //     text: '{\fnTimes New Roman\fs48\b0}asdfsadf sdsaada sdsd a {\k56}Red {\k70}blue {\k84}green {\k109}karaoke{\k56}Red {\k70}blue {\k84}green {\k109}karaoke',
  //   }
  // ];

  SSA.parse(subFile, true);
  // RETURNS
  // [
  //   {
  //     start: 47100,
  //     end: 49100,
  //     text: 'asdfsadf sdsaada sdsd a Red blue green karaokeRed blue green karaoke'
  //   }
  // ];

convert(subArray: Array, [styles: String, [heading: String]]) -> String

Converts an array of formatted objects into an SSA string.

styles refers to the style definition heading located at the top of the file, this string is not validated so please ensure you pass in a valid format for SSA/ASS. If none is passed a default style block is used. I've created another module for the sole purpose of handling this portion of an SSA file https://github.com/padraigfl/subtitle-ssa-styler This style will always be called 'primary' so any passed in style needs to share that name.

heading operates the same as styles, except for the top most definitions of the subtitle file, there's very little reason to use this.

  var SSA = require('subtitle-ssa');
  var subObj = [

  ]
  SSA.convert(subFile);

toMS(ssaTime: String) -> Number

Converts hh:mm:ss.HH (HH for hundreths as that's SSA's default) to a millisecond integer

  var SSA = require('subtitle-ssa');
  SSA.toMS('00:00:01.11'); // returns 1110

toSsaTime(mseconds: Number) -> String

Opposite of toMS

  var SSA = require('subtitle-ssa');
  SSA.toSsaTime(1110); // returns '00:00:01.11'

Subtitle Object

The object format used is as follows

{
  start: 123, // start time of subtitle in milliseconds
  end: 456, // end time
  text: 'text', // the text displayed for the subtitle
  secondaryText: 'subtext', // text for displaying subtitles in a separate style, currently only used for output
}

It should be pretty easy to readapt for any other format if required. I may write up some gists to copy and paste for modules such as subtitles-parser. An optional fourth attribute exists for the ability to add captions, notes and secondary subtitle tracks; it will be styled under the name 'secondary'

Concessions

• Due to the considerable additional overhead involved, general styles are not preserved from an existing SSA file
• As this project stems from a project revolving around merging subtitle files, there are two lines of code which are specifically related to accommodating that but hopefully have other use cases
• Subtitles must be already in UTF-8 format, they seem to work regardless with latin alphabet characters if not but anything else is a wildcard.

Contribution Notes

• I don't really expect anyone to but if they do, please flag an issue first and I'll get back within a day
• When flagging an issue, please inform me of the subtitle file which failed and what the possible causes may have been
• Ideas for extra functionality and more optimised code are very strongly encouraged!

Thanks

I'd like to thank G. Santiago for giving me a great base to work from of how to prepare an npm package with his pretty wonderful looking subtitle.js package and I'm sure I'll refer to his README as I build mine.