alass

Introduction

alass is a command line tool to synchronize subtitles to movies.

It can automatically correct

• constant offsets
• splits due to advertisement breaks, directors cut, ...
• different framerates

The alignment process is not only fast and accurate, but also language-agnostic. This means you can align subtitles to movies in different languages.

alass stands for "Automatic Language-Agnostic Subtitle Synchronization". The theory and algorithms are documented in my bachelor's thesis and summarized in my bachelor's presentation.

Executable for Windows (64-bit)

Get the latest executable from here! Just download and extract the archive. The file alass.bat is the command line tool.

Executable for Linux (64-bit)

Get the latest executable from here! To run the executable, ffmpeg and ffprobe have to be installed. You can change their paths with the environment variables ALASSFFMPEGPATH (default ffmpeg) and ALASSFFPROBEPATH (default ffprobe).

Usage

The most basic command is:

$ alass movie.mp4 incorrect_subtitle.srt output.srt

You can also use alass to align the incorrect subtitle to a different subtitle:

$ alass reference_subtitle.ssa incorrect_subtitle.srt output.srt

You can additionally adjust how much the algorithm tries to avoid introducing or removing a break:

# split-penalty is a value between 0 and 1000 (default 7)
$ alass reference_subtitle.ssa incorrect_subtitle.srt output.srt --split-penalty 10

Values between 5 and 20 are the most useful. Anything above 20 misses some important splits and anything below 5 introduces many unnecessary splits.