Scaling & Resizing

FFmpeg's scale filter adjusts video dimensions. Always use -2 for the output height to ensure dimensions are divisible by 2 (required by many codecs).

Basic Scaling

# Scale to 720p (maintain aspect ratio)
ffmpeg -i input.mp4 -vf "scale=1280:-2" output.mp4

# Scale to 480p
ffmpeg -i input.mp4 -vf "scale=854:-2" output.mp4

# Scale to specific dimensions (ignore aspect ratio)
ffmpeg -i input.mp4 -vf "scale=1920:1080" output.mp4

# Scale to 50%
ffmpeg -i input.mp4 -vf "scale=iw*0.5:ih*0.5" output.mp4

# Scale to 2x
ffmpeg -i input.mp4 -vf "scale=iw*2:ih*2" output.mp4

Scaling with Encoding

# Scale + encode with H.264
ffmpeg -i input.mp4 -vf "scale=1280:-2" \
  -c:v libx264 -preset fast -crf 22 \
  -c:a aac output_720p.mp4

# Scale to 480p with fast encoding
ffmpeg -i input.mp4 -vf "scale=854:-2" \
  -c:v libx264 -preset ultrafast -crf 28 \
  -c:a aac output_480p.mp4

Upscaling vs Downscaling

# Upscale with fast bilinear (faster, lower quality)
ffmpeg -i input.mp4 -vf "scale=1920:1080:flags=bilinear" output.mp4

# Upscale with Lanczos (slower, better quality)
ffmpeg -i input.mp4 -vf "scale=1920:1080:flags=lanczos" output.mp4

# Scale to exactly 1920x1080 (crop or pad to fit)
ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" output.mp4

Letterbox / Pillarbox (Add Black Bars)

# Fit to 16:9 with black bars
ffmpeg -i input.mp4 -vf "scale=1280:720:force_original_aspect_ratio=decrease,pad=1280:720:(ow-iw)/2:(oh-ih)/2:setsar=1" \
  -c:v libx264 -preset fast -crf 22 output_padded.mp4

Scale with Crop Detection

# Detect crop automatically
ffmpeg -i input.mp4 -vf "cropdetect=limit=0:round=2" -frames:v 50 -f null -

# Use detected crop values
ffmpeg -i input.mp4 -vf "crop=1920:800:0:140" -c:v libx264 -preset fast output_cropped.mp4

Multiple Outputs at Once

# Create multiple resolutions
ffmpeg -i input.mp4 \
  -vf "scale=1920:-2" -c:v libx264 -preset fast -crf 22 -c:a aac -b:a 192k -sn -map 0:v:0 -map 0:a:0 output_1080p.mp4 \
  -vf "scale=1280:-2" -c:v libx264 -preset fast -crf 22 -c:a aac -b:a 128k -sn -map 0:v:0 -map 0:a:0 output_720p.mp4 \
  -vf "scale=854:-2" -c:v libx264 -preset fast -crf 24 -c:a aac -b:a 96k -sn -map 0:v:0 -map 0:a:0 output_480p.mp4

Rotate / Flip

# Rotate 90 clockwise
ffmpeg -i input.mp4 -vf "rotate=PI/2" -c:a copy output.mp4

# Rotate 90 counter-clockwise
ffmpeg -i input.mp4 -vf "rotate=-PI/2" -c:a copy output.mp4

# Flip horizontally
ffmpeg -i input.mp4 -vf "hflip" -c:a copy output.mp4

# Flip vertically
ffmpeg -i input.mp4 -vf "vflip" -c:a copy output.mp4

Scale Variables Reference

Variable	Description
iw	Input width
ih	Input height
ow	Output width
oh	Output height
in	Input frame number
on	Output frame number
sar	Input sample aspect ratio
dar	Input display aspect ratio