FFMPEG PAD 필터: 모든 화면 비율에 대한 레터박스 및 필라박스 비디오

Originally published at ffmpeg-micro.com

You have got a 4:3 video that needs to be 16:9. Or a landscape clip that needs to fit a 9:16 vertical frame. Scaling alone either distorts the image or leaves the wrong dimensions. FFmpeg’s pad filter adds bars (black or any color) to fill the gap without touching a single pixel of your actual video.

Quick Answer: Pad to a Target Aspect Ratio

Letterbox a 4:3 video into a 16:9 frame with centered black bars:

ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black" output.mp4

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This first scales the video to fit inside 1920×1080 without distortion, then pads the remaining space with black. Two filters, one command.

How the pad Filter Works

The pad filter syntax:

pad=width:height:x:y:color

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• width and height set the total canvas size
• x and y position the video on that canvas
• color fills the empty space (default is black)

Dynamic Centering with Expressions

Instead of hardcoding pixel values, use FFmpeg built-in variables:

ffmpeg -i input.mp4 -vf "pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black" output.mp4

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• ow = output width, oh = output height
• iw = input width, ih = input height

This centers any input resolution on the target canvas.

Social Media Aspect Ratio Recipes

YouTube / landscape (16:9):

ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black" output.mp4

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Instagram Reels / TikTok / Shorts (9:16):

ffmpeg -i input.mp4 -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black" output.mp4

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Instagram square (1:1):

ffmpeg -i input.mp4 -vf "scale=1080:1080:force_original_aspect_ratio=decrease,pad=1080:1080:(ow-iw)/2:(oh-ih)/2:black" output.mp4

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Custom Bar Colors

# White bars
ffmpeg -i input.mp4 -vf "pad=1920:1080:(ow-iw)/2:(oh-ih)/2:white" output.mp4

# Hex color (dark blue)
ffmpeg -i input.mp4 -vf "pad=1920:1080:(ow-iw)/2:(oh-ih)/2:0x1a1a2e" output.mp4

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Pad via the FFmpeg Micro API

If you are automating video processing in a pipeline, you can run the same pad filter through an API call:

curl -X POST https://api.ffmpeg-micro.com/v1/transcodes \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "inputs": [{"url": "https://example.com/video.mp4"}], "outputFormat": "mp4", "options": [{"option": "-vf", "argument": "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black"}] }'

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Get a free API key at ffmpeg-micro.com to try it.

Common Pitfalls

• Padding without scaling first causes errors if input is larger than pad dimensions
• Odd dimensions break H.264/H.265 encoding
• Using pad when you need crop: pad adds space, crop removes it