srt_delay.py

… is a small Python 3 script that you can use to advance or delay the timings of a subtitle file in the .srt file format.

How it works

We will demonstrate srt_delay.py using the subtitles for the open-source movie Elephants Dream. The file can be downloaded from this repo (sample_input.srt) or from Wikimedia Commons.

Here is what the input file looks like:

$ head sample_input.srt
1
00:00:15,000 --> 00:00:17,951
At the left we can see...

2
00:00:18,166 --> 00:00:20,083
At the right we can see the...

3
00:00:20,119 --> 00:00:21,962

Each line contains either an index number for the subtitle (1), the subtitle’s timing (00:00:18,166 --> 00:00:20,083), or the subtitle text itself.

Delaying subtitles

Suppose we want to delay the subtitles by 1 hour and 5 minutes. We can pass this interval in .srt timestamp format (01:05:00,000) to srt_delay with the -d or --delay flag:

$ python3 srt_delay.py sample_input.srt -d 01:05:00,000 | head
1
01:05:15,000 --> 01:05:17,951
At the left we can see...

2
01:05:18,166 --> 01:05:20,083
At the right we can see the...

3
01:05:20,119 --> 01:05:21,962

Advancing subtitles

Suppose we want to advance the subtitles by 1.5 seconds. We can pass this interval in .srt timestamp format (00:00:01,500) to srt_delay.py with the -a or --advance flag:

$ python3 srt_delay.py sample_input.srt -a 00:00:01,500 | head
1
00:00:13,500 --> 00:00:16,451
At the left we can see...

2
00:00:16,666 --> 00:00:18,583
At the right we can see the...

3
00:00:18,619 --> 00:00:20,462

Typical usage

By default, srt_delay.py prints to standard output. In most cases, you will want to save the output to another file:

$ python3 srt_delay.py sample_input.srt -a 00:00:01,500 > sample_input_advanced_by_1.5s.srt

Bugs

If you find one, submit a PR or email me at maxkapur@gmail.com.