Capski CLI

A fast, Rust video subtitle pipeline that:

• Extracts audio from a video using ffmpeg
• Transcribes speech into text with precise timestamps using whisper_rs
• Generates styled karaoke-style ASS subtitles (with word-level highlighting)
• Burns subtitles into videos or overlays on new video, image, or solid color backgrounds with ffmpeg

Note

More examples are available in the example directory.

output_bg_image.mp4

Important

Tested on macOS only.

The instructions below assume you’re on a Mac (using Homebrew).

Engineering Requirements Document

The Engineering Requirements Document (ERD) is available here :

-> ERD on Google Docs

Getting started

1. Install ffmpeg

brew install ffmpeg

2. Install Capski

You can now install Capski using Rust Cargo.

cargo install --path .

3. Run Capski

Basic transcription (auto-detects language):

capski --input "example/input_audio.wav"

You can also translate your non-English audio to English:

capski --input "japanese_audio.wav" --translate

Also explicity set the source language to translate to English:

capski --input "french_audio.wav" --language FR --translate

Note

Capski uses Whisper to transcribe audio. If you want to translate non-English speech into English subtitles, use the --translate flag along with the --language option to specify the source language (e.g., fr for French, es for Spanish).

📌 Whisper only supports translation into English. Translating English into other languages is not supported.

This runs the pipeline end-to-end:

• extracts or processes audio,
• transcribes with Whisper,
• generates subtitles,
• burns subtitles into a new video.

Configuration

In the style.json file, you control:

• Subtitle text styling: font, size, colors, alignment
• Background style: solid color, image, or looping video

You can control your background type to be either solid, video, or image. Here are the 3 way to configure it:

• Video Background

{
  "background": {
    "type": "video",
    "solid_color": null,
    "video_path": "assets/bg_example.mp4",
    "image_path": null
  }
}

• Image Background

{
  "background": {
    "type": "image",
    "solid_color": null,
    "video_path": null,
    "image_path": "assets/bg_image.jpg"
  }
}

• Solid Background

{
  "background": {
    "type": "solid",
    "solid_color": "#101020",
    "video_path": null,
    "image_path": null
  }
}

Note

You can find the example of each of those configurations in the example directory. In assets directory, you will find the video and image backgrounds used in those examples.