openclaw/.agent/skills/heygen/rules/captions.md

name	description	metadata
captions	Auto-generated captions and subtitle options for HeyGen videos	tags captions, subtitles, accessibility, srt

Video Captions

HeyGen can automatically generate captions (subtitles) for your videos, improving accessibility and engagement.

Enabling Captions

Captions can be enabled when generating a video:

const videoConfig = {
  video_inputs: [
    {
      character: {
        type: "avatar",
        avatar_id: "josh_lite3_20230714",
        avatar_style: "normal",
      },
      voice: {
        type: "text",
        input_text: "Hello! This video will have automatic captions.",
        voice_id: "1bd001e7e50f421d891986aad5158bc8",
      },
    },
  ],
  // Caption settings (availability varies by plan)
  caption: true,
};

Caption Configuration Options

interface CaptionConfig {
  // Enable/disable captions
  enabled: boolean;

  // Caption style
  style?: {
    font_family?: string;
    font_size?: number;
    font_color?: string;
    background_color?: string;
    position?: "top" | "bottom";
  };

  // Language for caption generation
  language?: string;
}

Caption Styles

Basic Captions

const config = {
  video_inputs: [...],
  caption: true, // Enable with default styling
};

Styled Captions

const config = {
  video_inputs: [...],
  caption: {
    enabled: true,
    style: {
      font_family: "Arial",
      font_size: 32,
      font_color: "#FFFFFF",
      background_color: "rgba(0, 0, 0, 0.7)",
      position: "bottom",
    },
  },
};

Multi-Language Captions

For videos in different languages, captions are generated based on the voice language:

// Spanish video with Spanish captions
const spanishConfig = {
  video_inputs: [
    {
      character: {
        type: "avatar",
        avatar_id: "josh_lite3_20230714",
        avatar_style: "normal",
      },
      voice: {
        type: "text",
        input_text: "¡Hola! Este video tendrá subtítulos en español.",
        voice_id: "spanish_voice_id",
      },
    },
  ],
  caption: true,
};

Working with SRT Files

Downloading SRT

After video generation, you may be able to download the SRT file:

async function downloadSrt(videoId: string): Promise<string> {
  const response = await fetch(
    `https://api.heygen.com/v1/video/${videoId}/srt`,
    { headers: { "X-Api-Key": process.env.HEYGEN_API_KEY! } }
  );

  if (!response.ok) {
    throw new Error("Failed to download SRT");
  }

  return response.text();
}

SRT File Format

Standard SRT format:

1
00:00:00,000 --> 00:00:03,000
Hello! This video will have

2
00:00:03,000 --> 00:00:06,000
automatic captions generated.

3
00:00:06,000 --> 00:00:09,000
They sync with the audio.

Using Custom SRT

For video translation, you can provide your own SRT:

const translationConfig = {
  input_video_id: "original_video_id",
  output_languages: ["es-ES", "fr-FR"],
  srt_key: "path/to/custom.srt", // Custom SRT file
  srt_role: "input", // "input" or "output"
};

Caption Positioning

Bottom (Default)

Standard position for most videos:

caption: {
  enabled: true,
  style: {
    position: "bottom"
  }
}

Top

For videos where bottom space is occupied:

caption: {
  enabled: true,
  style: {
    position: "top"
  }
}

Accessibility Best Practices

1. Always enable captions - Improves accessibility for deaf/hard-of-hearing viewers
2. Use high contrast - White text on dark background or vice versa
3. Readable font size - At least 24px for standard video, larger for mobile
4. Don't cover important content - Position captions away from key visual elements
5. Sync timing - Ensure captions match audio timing accurately

Caption Helper Functions

interface CaptionStyle {
  font_family: string;
  font_size: number;
  font_color: string;
  background_color: string;
  position: "top" | "bottom";
}

const captionPresets: Record<string, CaptionStyle> = {
  default: {
    font_family: "Arial",
    font_size: 32,
    font_color: "#FFFFFF",
    background_color: "rgba(0, 0, 0, 0.7)",
    position: "bottom",
  },
  minimal: {
    font_family: "Arial",
    font_size: 28,
    font_color: "#FFFFFF",
    background_color: "transparent",
    position: "bottom",
  },
  bold: {
    font_family: "Arial",
    font_size: 36,
    font_color: "#FFFFFF",
    background_color: "rgba(0, 0, 0, 0.9)",
    position: "bottom",
  },
  branded: {
    font_family: "Roboto",
    font_size: 30,
    font_color: "#00D1FF",
    background_color: "rgba(26, 26, 46, 0.9)",
    position: "bottom",
  },
};

function createCaptionConfig(preset: keyof typeof captionPresets) {
  return {
    enabled: true,
    style: captionPresets[preset],
  };
}

Social Media Caption Considerations

TikTok / Instagram Reels

• Position captions in center or upper portion
• Avoid bottom 20% (covered by UI elements)
• Use larger font sizes for mobile viewing

const socialCaptions = {
  enabled: true,
  style: {
    font_size: 42,
    position: "top", // Avoid bottom UI elements
  },
};

YouTube

• Standard bottom captions work well
• YouTube also supports closed captions upload

LinkedIn

• Captions highly recommended (many watch without sound)
• Professional styling preferred

Limitations

• Caption styles may be limited depending on your subscription tier
• Some advanced caption features may require the web interface
• Multi-speaker caption detection may have limited availability
• Caption accuracy depends on audio quality and speech clarity

Integration with Video Translation

When using video translation, captions are automatically handled:

// Video translation includes caption generation
const translationConfig = {
  input_video_id: "original_video_id",
  output_languages: ["es-ES"],
  // Captions generated in target language
};

See video-translation.md for more details.