srt-cli

A small Command Line Input (CLI) that takes subtitle text and converts it into a .srt file.

Why?

While watching re:zero season 3 I noticed the re:zero break time season 3 was airing simultaneously.

I wanted to watch the break time episodes with subtitles but couldn't find any. That is until I saw a commentor by the name of @KakoeiSbi who translated the break time episodes in a specific format.

I decided then to create a CLI that would take the text and convert it into a .srt file and optionally download the matching video from YouTube.

Optional YouTube Flow

If you paste a YouTube URL at the first prompt, the CLI will:

1. Fetch the video metadata with yt-dlp
2. Download the video with yt-dlp
3. Infer the video length automatically
4. Create a temporary .srt
5. Create a new .subbed.mkv video with the subtitles embedded using ffmpeg
6. Delete the temporary .srt and the original downloaded video when embedding succeeds

While the CLI is downloading, parsing, or writing files, it now shows a small loading state in the terminal.

If you press Enter instead, the CLI falls back to the original manual flow and asks for the video length and output file name.

To use the YouTube flow, make sure yt-dlp and ffmpeg are installed and available in your PATH.

You can also pass the URL directly as the first CLI argument:

bun run src/index.ts "https://www.youtube.com/watch?v=..."

If the URL contains ? or &, wrap it in quotes so your shell does not interpret it.

After loading a YouTube video, the CLI automatically tries to import subtitle text from a YouTube comment left by @KakoeiSbi. The author matching is fuzzy, so it can still match handle, channel URL, or similar author identifiers returned by yt-dlp. If no matching parseable comment is found, it falls back to manual subtitle entry.

When a video is downloaded from YouTube, the CLI creates a final .subbed.mkv file with the subtitles embedded as a subtitle track. If ffmpeg succeeds, the temporary .srt and the original downloaded video are deleted. If ffmpeg fails, those intermediate files are left in place so you can recover manually.

Run script from npm

npx srt-cli

Then follow the CLI steps.

The text entered should follow the format:

(mm:ss) <character>: "<dialogue>"

Each subtitle should be entered on its own line.

You can also place multiple subtitle entries on the same line by separating them with #:

(mm:ss) <character>: "<dialogue>" # mm:ss <character>: "<dialogue>"

The comment import feature expects the same subtitle format inside the YouTube comment text, but the comment can also include extra commentary before, after, or between subtitle lines. The CLI now extracts only the lines that look like subtitles.

Run Locally

To install dependencies:

bun install

To run:

bun run src/index.ts

The first prompt accepts an optional YouTube URL. Leave it blank to use manual mode.

You can skip that first prompt by passing a quoted YouTube URL as the first argument.

This project was created using bun init in bun v1.1.30. Bun is a fast all-in-one JavaScript runtime.