ionutp / gpt-subtrans

Project using OpenAI/ChatGPT to translate subtitle files

GPT-Subtrans

GPT-Subtrans is an open source subtitle translator that uses OpenAI's LLMs as a translation service. It can translate subtitles between any language pairs supported by the language model. You will need an OpenAI API key from https://platform.openai.com/account/api-keys to use the translator. If you are on the free trial the speed will be severely restricted.

Note: GPT-Subtrans requires an active internet connection to access the OpenAI API. Subtitles are sent to OpenAI's servers for translation, so their privacy policy applies: https://openai.com/policies/privacy-policy.

New

I have been unable to get PyInstaller to build universal binaries on MacOS for several recent versions, so I can only provide releases for Apple Silicon. The latest code should still run on Intel Macs if you install from source.

Installation

For most users the packaged release is the easiest way to use the program. Simply unzip to a folder and run gui-subtrans.exe. You will be prompted for some basic settings on first run.

Installing from source

For other platforms, or if you want to modify the program, you will need to have Python 3.10+ and pip installed on your system, then follow these steps.

1. Clone the GPT-Subtrans repository onto your local machine using the following command:

    git clone https://github.com/machinewrapped/gpt-subtrans.git

The easiest setup method for most users is to run install.bat or install.sh/install-mac.sh at this point and enter your API key when prompted. You can then skip the remaining steps.

2. Create a new file named .env in the root directory of the project. Add your OpenAI API key to the .env file like this:

    API_KEY=<your_api_key_here>

3. Create a virtual environment for the project by running the following command in the root folder to create a local environment for the Python interpreter.:

    python -m venv envsubtrans

4. Activate the virtual environment by running the appropriate command for your OS:

    .\envsubtrans\Scripts\activate
    .\envsubtrans\bin\activate

5. Install the required libraries using pip by running the following command in your terminal to install the project dependencies (listed in the requirements.txt file):

    pip install -r requirements.txt

Note that steps 3 and 4 are optional, but they can help prevent conflicts with other Python applications.

Usage

GUI

The easiest way for most people to use GPT-Subtrans is with the Subtrans GUI. After installation launch the GUI with the gui-subtrans command or shell script, and in theory the rest should be self-explanatory. See the project wiki for details on how to use the program.

Command Line

GPT-Subtrans can still be used as a console command for scripting, or if that's what you prefer. The most basic usage is:

gpt-subtrans <path_to_srt_file> --target_language <target_language>

This will activate the virtual environment and call the translation script with default parameters. If the target language is not specified, the default is English.

Note: Remember to activate the virtual environment every time you work on the project.

The program works by dividing the subtitles up into small batches and sending each one to Chat GPT in turn. It is likely to take a long time to complete, and can potentially make hundreds of API calls.

By default The translated subtitles will be written to a new SRT file with the suffix -GPT added to the original filename, in the same directory.

For more control over the translation process it is recommended to use an IDE such as VS Code.

It is highly recommended to use Subtitle Edit's (https://www.nikse.dk/subtitleedit) "Fix Common Errors" on the results to clean them up (e.g. add line breaks).

Advanced usage

There are a number of command-line arguments that offer more control over the translation process. Many of these work for the GUI as well as the command line, though the more common options can more easily be set in the GUI.

Many of these settings can be configured in the .env file too, using a similar name NAME_IN_CAPS with underscores, along with some other configuration options. See Options.py for the full list. Arguments specified on the command line have priority.

• -o, --output: Specify the filename for the translated subtitles.

• -p, --project: Read or Write a project file for the subtitles being translated. More on this below.

• -r, --ratelimit: Maximum number of batches per minute to process. If you're on the OpenAI free trial this to 2 or 3.

• -m, --moviename: Optionally specify the name of the movie to give context to the translator.

• --description: A brief description of the film to give context. Less is more here, otherwise the AI can start improvising.

• -n, --name, --names: Optionally provide (a list of) names to use in the translation (gpt4 and gpt-3.5-turbo-instruct are more likely to actually use them).

• -s, --substitution: A pair of strings separated by ::, to substitute in either source or translation, or the name of a file containing a list of such pairs.

• --scenethreshold: Number of seconds between lines to consider it a new scene.

• --batchthreshold: Number of seconds between lines to consider starting a new batch of subtitles to translate. Not used by the new batcher. Smaller batches take longer and cost more, but introduce more sync points and reduce the scope for the AI to drift.

• --minbatchsize: Minimum number of lines to consider starting a new batch to send to the AI. Higher values result in faster and cheaper translations but increase the risk of desyncs.

• --maxbatchsize: Maximum number of lines before starting a new batch is compulsory. This needs to take into account the token limit for the model being used, but the "optimal" value depends on many factors, so some experimentation is encouraged. Higher values make the translation more cost-effective, but increase the risk of the AI getting confused or improvising, triggering expensive retries.

• --maxbatchsize: Maximum number of lines before starting a new batch is compulsory. Higher values make the translation faster and cheaper, but increase the risk of the AI getting confused or improvising.

• -k, --apikey: Your OpenAI API Key (https://platform.openai.com/account/api-keys). Not required if it is set in .env

• -b, --apibase: API base URL. Used for third-party API endpoints. if it is not set, the default URL for the model will be used.

• -t, --temperature: A higher temperature increases the random variance of translations. Default 0.

• -i, --instruction: An additional instruction for the AI indicating how it should approach the translation.

• -f, --instructionfile: Name/path of a file to load AI system instructions from (otherwise the default instructions.txt is used).

• --maxlines: Maximum number of batches to process. To end the translation after a certain number of lines, e.g. to check the results.

To use any of these arguments, add them to the command-line after the path to the SRT file. For example:

gpt-subtrans path/to/my/subtitles.srt --moviename "My Awesome Movie" --ratelimit 10 -s cat::dog

Project File

Note If you are using the GUI a project file is created automatically when you open a subtitle file for the first time, and the project is generally updated automatically when anything changes.

The --project argument or PROJECT .env setting can take a number of values, which control whether and when an intermediate file will be written to disc.

The default setting is None, which means the project file is neither written nor read, the only output of the program is the final translation.

If the argument is set to True then a JSON file will be created with the .subtrans extension, containing details of the translation process, and it will be updated as the translation progresses.

Writing a project file allows, amongst other things, resuming a translation that was interrupted. Set the argument to resume to enable this.

Other valid options include preview, reparse and retranslate. These are probably only useful if you're modifying the code, in which case you should be able to see what they do.

Version History

Version 0.5 adds support for gpt-instruct models and a refactored code base to support different translation engines. For most users, the recommendation is still to use the gpt-3.5-turbo-16k model with batch sizes of between (10,100) lines, for the best combination of performance/cost and translation quality.

Version 0.4 features significant optimisations to the GUI making it more responsive and usable, along with numerous bug fixes.

Version 0.3 featured a major effort to bring the GUI up to full functionality and usability, including adding options dialogs and more, plus many bug fixes.

Version 0.2 employs a new prompting approach that greatly reduces desyncs caused by GPT merging together source lines in the translation. This can reduce the naturalness of the translation when the source and target languages have very different grammar, but it provides a better base for a human to polish the output.

The instructions have also been made more detailed, with multiple examples of correct output for GPT to reference, and the generation of summaries has been improved so that GPT is better able to understand the context of the batch it is translating. Additionally, double-clicking a scene or batch now allows the summary to be edited by hand, which can greatly improve the results of a retranslation and of subsequent batches or scenes. Individually lines can also be edited by double-clicking them.

Contributing

Contributions from the community are welcome! To contribute to GPT-Subtrans, follow these steps:

Fork the repository onto your own GitHub account.

Clone the repository onto your local machine using the following command:

git clone https://github.com/your_username/GPT-Subtrans.git

Create a new branch for your changes using the following command:

git checkout -b feature/your-new-feature

Make your changes to the code and commit them with a descriptive commit message.

Push your changes to your forked repository.

Submit a pull request to the main GPT-Subtrans repository.

Acknowledgements

This project uses several useful libraries:

• openai, of course (https://platform.openai.com/docs/libraries/python-bindings)
• srt (https://github.com/cdown/srt)
• requests (https://github.com/psf/requests)
• regex (https://github.com/mrabarnett/mrab-regex)

For the GUI:

• pyside6 (https://wiki.qt.io/Qt_for_Python)
• events (https://pypi.org/project/Events/)
• darkdetect (https://github.com/albertosottile/darkdetect)
• appdirs (https://github.com/ActiveState/appdirs)

For bundled versions:

• python (https://www.python.org/)
• pyinstaller (https://pyinstaller.org/)

License

GPT-Subtrans is licensed under the MIT License. See LICENSE for the 3rd party library licenses.