Subtitles Stretching by Factor

A function that stretches subtitles by a given factor - Python

Introduction

A function that:

• reads .srt subtitle file
• multiplies each individual subtitle by a specified factor e.g. 1.04
• saves to a new .srt subtitle file

Practical use

When the speed or duration of a film or video is changed the subtitles have to be adjusted. This python function accomplishes it automatically by simply pointing at the .srt file and specifying the factor of the speed change.

I ran into this task when I needed to convert the film from 25 fps to 24 fps by increasing the speed/duration of the film by 25/24 or 1.041667.

Input

Standard .srt subtitle file in the following format:

1
00:00:03,400 --> 00:00:06,177
In this lesson, we're going to
be talking about finance. And

2
00:00:06,177 --> 00:00:10,009
one of the most important aspects
of finance is interest.

...

23
00:01:46,860 --> 00:01:49,970
find an institution that will pay
me a higher interest rate.

Output

Standard .srt subtitle file that can be imported in any video editing software or straight to Vimeo or YouTube.

In the example below subtitles are stretched by the factor of 1.041667.

1
00:00:03,541 --> 00:00:06,434
In this lesson, we're going to
be talking about finance. And

2
00:00:06,434 --> 00:00:10,426
one of the most important aspects
of finance is interest.

...

23
00:01:51,312 --> 00:01:54,552
find an institution that will pay
me a higher interest rate.

Importing to video editor FinalCut Pro

Launch FinalCut Pro and select File -> Import -> Captions, then select .srt file to import subtitles into Video Editing software.