DualSub

DualSub can be used to translate subtitle and merge two separate translation files into a single one, so that you can watch a movie with subtitles in two different languages.

It can come in handy to non-native English speakers who want to watch movies in English, while also viewing the translation in their own language, so as to understand idioms and more complex expressions.

The application is very easy to work with, displaying all the options within a single window. You can easily select the subtitles you want to merge (in SRT format only) and customize the output location.

There are various other settings that you can experiment with, such as changing the timing persistence and modifying the synchronization mode, adjusting the screen width, customizing the subtitle font and size or change the character encoding mode. DualSub is compatible with various languages, including Arabic, Japanese or Russian and therefore, it supports multiple character sets, so as to allow translations using the Cyrillic and the Latin alphabet.

Aside from merging two separate SRT files, DualSub comes with translation capabilities between the supported languages. You can instruct it to translate the input file only or merge the two translations and create a single SRT file that displays two separate translations for each line.

The processing speed is acceptable, but it highly depends on the size of the subtitle file. As such, a SRT file with a large number of lines might take a while to be translated.

The purpose of DualSub is to make it possible to watch two sets of subtitles simultaneously, which helps the viewers improve their English (or other language) skills while enjoying their favorite movie. It's safe to say it is an entertaining way to learn English.