nicoize

Add NicoNico-style scrolling comments (text + emotes) onto a video using FFmpeg.

Install

Requires FFmpeg/FFprobe in PATH and Node.js >= 18.

npm install nicoize

Usage (API)

import { nicoize, type NicoizeData } from "nicoize";

const data: NicoizeData = {
  chats: [
    /* ... */
  ],
};

await nicoize({
  data,
  videoPath: "input.mp4",
  outputPath: "output.mp4",
  fontFile: "NotoSansJP.ttf",
});

options:

• fontFile (required): path to a font that supports Japanese glyphs.
• fontSizeRatio (default 0.08): font size relative to video height.
• scrollDurationSeconds (default 4): seconds from first appearance to fully off-screen. Longer text moves faster to meet this duration.
• fontColor (default white): font color.
• strokeColor (default black): stroke color.
• safeAreaRatio (default 0.05): top/bottom margin ratio.
• videoCodec (default libx264): crf (20), preset (veryfast).
• suppressFfmpegOutput (default true): hide FFmpeg logs.
• onLog: callback to receive FFmpeg stderr lines.

Usage (CLI)

npx nicoize --chat sample.json --video input.mp4 --font-file NotoSansJP.ttf --output output.mp4 --overwrite

• Required flags: --chat, --video, --font-file
• Optional: --output, --font-size-ratio, --duration, --font-color, --stroke-color, --safe-area-ratio, --codec, --crf, --preset, --overwrite, --ffmpeg-verbose.

Sample chat data

{
  "chats": [
    {
      "offsetSeconds": 3,
      "fragments": [
        {
          "type": "text",
          "text": "Nice to meet you!"
        }
      ]
    },
    {
      "offsetSeconds": 8,
      "fragments": [
        {
          "type": "emote",
          "url": "https://example.com/emote.png"
        },
        {
          "type": "text",
          "text": "here we go"
        }
      ]
    }
  ]
}

Emotes can be static images or animated GIFs.

License

ISC