Sustainability of Digital Formats: Planning for Library of Congress Collections

This document will cover information about VobSub Subtitle Index Files (VobSub IDX), the plain text files used by the VobSub software application (see History), sometimes referred to as VobSub Subtitles file, as it is always accompanied by a SUB file. Information referenced from FileInfo.com, FileFormat.com, and Lifewire.com.

VobSub IDX files are subtitle index files used to display subtitle text on videos. VobSub IDX files are created and used by VobSub, a free program that lets users extract subtitles from DVDs and create text-based subtitles. The VobSub IDX file contains a list of metadata and timestamps used to point to the subtitlesinside the SUB file (contains images that include subtitle text).

Structure of VobSub IDX:

VobSub IDX files are generated as plain text files storing metadata information at the start of the file, subtitle settings begin with a ‘#’, followed by timestamps and image references beginning with ‘timestamp:’.

VobSub IDX Text File Example:
(source)

# VobSub index file, v7 (do not modify this line!)
#
# To repair desyncronization, you can insert gaps this way:
# (it usually happens after vob id changes)
#
# delay: [sign]hh:mm:ss:ms
#
# Where:
# [sign]: +, - (optional)
# hh: hours (0 <= hh)
# mm/ss: minutes/seconds (0 <= mm/ss <= 59)
# ms: milliseconds (0 <= ms <= 999)
#
# Note: You can't position a sub before the previous with a negative value.
#
# You can also modify timestamps or delete a few subs you don't like.
# Just make sure they stay in increasing order.


# Settings

# Original frame size
size: 720x576

# Origin, relative to the upper-left corner, can be overloaded by aligmentalignment
org: 0, 0

# Image scaling (hor,ver), origin is at the upper-left corner or at the alignment coord (x, y)
scale: 100%, 100%

# Alpha blending
alpha: 100%

# Smoothing for very blocky images (use OLD for no filtering)
smooth: OFF

# In millisecs
fadein/out: 50, 50

# Force subtitle placement relative to (org.x, org.y)
align: OFF at LEFT TOP

# For correcting non-progressive desync. (in millisecs or hh:mm:ss:ms)
# Note: Not effective in DirectVobSub, use "delay: ... " instead.
time offset: 0

# ON: displays only forced subtitles, OFF: shows everything
forced subs: OFF

# The original palette of the DV
D palette: 000000, 828282, 828282, 828282, 828282, 828282, 828282, ffffff, 828282, bababa, 828282, 828282, 828282, 828282, 828282, 828282

# Custom colors (transp idxs and the four colors)
custom colors: OFF, tridx: 1000, colors: 000000, bababa, 828282, 000000

# Language index in use
langidx: 0

# English
id: en, index: 0
# Decomment next line to activate alternative name in DirectVobSub / Windows Media Player 6.x
# alt: English
# Vob/Cell ID: 1, 1 (PTS: 0)
timestamp: 00:01:25:880, filepos: 000003800
timestamp: 00:01:46:160, filepos: 000008000
timestamp: 00:02:08:880, filepos: 00000c800
# Vob/Cell ID: 1, 2 (PTS: 222840)
timestamp: 00:03:58:800, filepos: 000011000
timestamp: 00:04:00:680, filepos: 000016800
timestamp: 00:04:04:640, filepos: 00001d800

Uses of VobSub IDX:

When using VobSub programs or media players that support VobSub IDX/SUB Subtitle format, users can play back subtitles along with the movie the subtitles were created for. The VobSub IDX/SUB format also has support for multiple tracks and can be embedded in MP4 (Nero) and Matroska (MKV) files.

Little documentation. A variety of websites describe the VobSub IDX format and give a description of the text file outline, but no unified format standard was found.

VideoHelp.com has a link to the latest software version, VobSub 2.23.

VideoHelp.com states that VobSub as ‘No Longer Developed.” See History.

Comments welcome.

No formal documentation found, but informal information found at FileFormat.com.

Comments welcome.

Limited information. Although VobSub is no longer being developed, users can still download the latest version of the software, VobSub 2.23, which contains a subtitle filter and subtitle utilities that can extract, covert, cut, and join VobSub IDX/SUB files from DVDs.

An archived guide on Afterdawn.com, titled Subtitle Formats Explained (date not found),stated that “VobSub subtitles have become very common because it’s easy to get them from DVDs...However, in recent years the growing popularity of the Matroskamultimedia container has been a bonus for people who prefer subtitle format because it can be muxed into MKV files so it’s no longer necessary to have a separate file for subtitles.”

Comments welcome.

No known license or patent concerns generation and use of the format VobSub IDX.

Comments welcome.

VobSub IDX are generated and saved as plain text, hence readable with any text editor.

Comments welcome.

VobSub IDX contain metadata information that is read by media players for parameters such subtitle color, position, and when and what order to show the images the SUB file contains.

Comments welcome.

None beyond availability of supporting software.

Comments welcome.

None.

Comments welcome.

Good support. VobSub IDX files are plain text, supporting the standard ASCII characters, including numbers, symbols, and spaces.

Comments welcome.

Low support. VobSub IDX files plain text does not support any type of text formatting.

Comments welcome.

Some support. VobSub IDX file metadata allows users to set what the text color is, where the text should appear, and when/what order to show SUB file images.

Comments welcome.

Little to no information on VobSub IDX file’s support of mathematics, chemical formulae, diagrams, etc.

Comments welcome.

None known. See notes for information about different uses of IDX files.

Comments welcome.

VobSub IDX files, when created in conjunction with SUB files, are often called VobSubSubtitles, as they are created and used by the VobSub software to extract subtitles from DVDs for users to view alongside the movie they are watching. Limited online information about the VobSub software history.

According to Wikipedia DirectVobSub’s page, after the last release of VobSub 2.23, development stopped.

DirectVobSub, also known as VSFilter, is a software add-on for Microsoft Windows that can read external subtitle files. It was formerly a part of the VobSub application. VSFilter was part of the guliverkli project on SourceForge’s website, but development of that project ended with version 2.37 in 2005. Guliverkl2 project, known as DirectVobSub started in 2007, and thensometime after MPC-HC sources took over the project, but that shutdown in 2017 due to lack of developers.