Enables a fixed setting of subtitle time offsets to a selected SubRip (srt) file via the CLI by overwriting its time intervals.

It differs from utilizing subtitle shifts inside an arbitrary media player, due to permenently applying timeline changes, not just during an active session — sync audio and subtitle tracks once, use them multiple times.

Fetch the latest version:

python3 -m pip install git+https://github.com/tainn/[email protected]

A negative offset value hastens, while a positive offset value delays the subtitles.

The script can be executed via the CLI with or without a -p or --path parameter. If omitting the use, the code will look for a srt file in the current working directory and exit if none or more than one match is found. An exception to this case are srt files that abide by a glob match: *old-[0-9][0-9].srt. This is done in order to allow rapid readjustments (up to 100 times) when attempting to set an audio-subtitle sync via trial and error — see output.

$ subsync --help
usage: subsync [-h] [-p PATH] offset

positional arguments:
  offset                amount of seconds to shift (+-0.000)

options:
  -h, --help            show this help message and exit
  -p PATH, --path PATH  absolute or relative path to the file

The output is a new srt file with newly set timelines, with the old file being kept and renamed to -old-{incr}.srt, where {incr} is a serial increment of old srt files in the same directory, starting with 00 and ending with 99, allowing for up to 100 buffered files.

The SubRip (srt) files usually follow their file format. This code assumes that to be the form of the passed file and may error out if the form is different. Even though it rarely happens, the culprit for such mismatches is usually a type of bad-form advertising of a subtitle group at the top of the file. Either manually delete that segment or change it to fit the format.