srt_equalizer 0.1.12
Transform subtitle line lengths, splitting into multiple subtitle fragments if necessary. 
License: MIT
Requires Python: <4.0,>=3.8

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# SRT Equalizer

A Python module to transform subtitle line lengths, splitting into multiple subtitle
fragments if necessary. Useful to adjust automatic speech recognition outputs from e.g. [Whisper](https://github.com/openai/whisper) to a more convenient size.

This library works for all languages where spaces separate words.

## Installing

`pip install srt_equalizer`

## Example

An SRT file containing lines over a certain length can be adjusted to a maximum line length for better readability on screen.

```
1
00:00:00,000 --> 00:00:04,000
Good evening. I appreciate you giving me a few minutes of your time tonight

2
00:00:04,000 --> 00:00:11,000
so I can discuss with you a complex and difficult issue, an issue that is one of the most profound of our time.
```

To adjust line length to a maximum length of 42 chars you can use SRT equalizer like this:

```python

from srt_equalizer import srt_equalizer

srt_equalizer.equalize_srt_file("test.srt", "shortened.srt", 42)
```

...they are split into multiple fragments and time code is adjusted to the
approximate proportional length of each segment while staying inside the time
slot for the fragment.

```
1
00:00:00,000 --> 00:00:02,132
Good evening. I appreciate you giving me

2
00:00:02,132 --> 00:00:04,000
a few minutes of your time tonight

3
00:00:04,000 --> 00:00:06,458
so I can discuss with you a complex and

4
00:00:06,458 --> 00:00:08,979
difficult issue, an issue that is one of

5
00:00:08,979 --> 00:00:11,000
the most profound of our time.
```

### Algorithms
By default, this script uses `greedy` algorithm which splits the text at the rightmost possible space.

An alternative splitting algorithm is `halving` which will split longer lines more evenly instead of always trying to use maximum line length. This prevents producing lines with isolated word remainders.

Another alternative is the `punctuation` algorithm that takes punctuation (commas, periods, etc.) into account. 

```python

from srt_equalizer import srt_equalizer

# use "greedy", "halving" or "punctuation" for the method parameter
srt_equalizer.equalize_srt_file("test.srt", "shortened.srt", 42, method='halving')
```

## Adjust Whisper subtitle lengths
Is is also possible to work with subtitle items produced from [Whisper](https://github.com/openai/whisper) with the following utility methods:

```python
split_subtitle(sub: srt.Subtitle, target_chars: int=42, start_from_index: int=1) -> list[srt.Subtitle]:

whisper_result_to_srt(segments: list[dict]) -> list[srt.Subtitle]:
```

Here is an example of how to reduce the lingth of subtitles created by Whisper. It assumes you have an audio file to transcribe called gwb.wav.

```python
import whisper
from srt_equalizer import srt_equalizer
import srt
from datetime import timedelta

options_dict = {"task" : "transcribe", "language": "en"}
model = whisper.load_model("small")
result = model.transcribe("gwb.wav", language="en")
segments = result["segments"]
subs = srt_equalizer.whisper_result_to_srt(segments)

# Reduce line lenth in the whisper result to <= 42 chars
equalized = []
for sub in subs:
    equalized.extend(srt_equalizer.split_subtitle(sub, 42))

for i in equalized:
    print(i.content)
```

## Quotes consideration

The method "split_by_punctuation" will try to take into account punctuation (commas, periods, etc.) when splitting the text.

This is to prevent trailing quotation characters when splitting text.

| Character | Unicode | Description |
|-----------|---------|-------------|
| ' | U+0027 | ASCII apostrophe |
| " | U+0022 | ASCII double quote |
| " | U+201C | Left double curly quote |
| " | U+201D | Right double curly quote |
| ' | U+2018 | Left single curly quote |
| ' | U+2019 | Right single curly quote |
| „ | U+201E | Double low-9 quote (German) |
| ‚ | U+201A | Single low-9 quote (German) |
| « | U+00AB | Left guillemet |
| » | U+00BB | Right guillemet |
| ‹ | U+2039 | Single left guillemet |
| › | U+203A | Single right guillemet |

## Contributing

This library is built with [Poetry](https://python-poetry.org). Checkout this repo and run `poetry install` in the source folder. To run tests use `poetry run pytest tests`.

To build a new release, create a new tag, build it and publish to pypi:
```
poetry run pytest tests
git tag v0.1.2
poetry build
poetry publish
```

If you want to explore the library start a `poetry shell`.