How to use FFmpeg Filter? What are the common video and audio filters?

FFmpeg Filter is one of the most powerful features in FFmpeg, allowing for various complex processing operations on audio and video.

Filter Basic Syntax

Filter Chain Syntax

bash
# Basic format
-filter "filter1=param1=value1:param2=value2,filter2=param1=value1"

# Complex filter chain
-filter_complex "[0:v]scale=1280:720[v];[0:a]volume=0.5[a];[v][a]concat=n=1:v=1:a=1"

Filter Label Explanation

• [0:v]: Video stream from input 0
• [0:a]: Audio stream from input 0
• [v]: Named output stream
• ;: Separator for different filter chains
• ,: Separator for filters in the same chain

Common Video Filters

Scale Filter

bash
# Fixed resolution
ffmpeg -i input.mp4 -vf "scale=1280:720" output.mp4

# Maintain aspect ratio
ffmpeg -i input.mp4 -vf "scale=1280:-1" output.mp4

# Scale by ratio
ffmpeg -i input.mp4 -vf "scale=iw/2:ih/2" output.mp4

# Limit maximum size
ffmpeg -i input.mp4 -vf "scale='min(1280,iw)':'min(720,ih)'" output.mp4

Crop Filter

bash
# Crop center area
ffmpeg -i input.mp4 -vf "crop=640:480" output.mp4

# Specify crop position
ffmpeg -i input.mp4 -vf "crop=640:480:10:10" output.mp4

# Crop bottom-right corner
ffmpeg -i input.mp4 -vf "crop=640:480:in_w-640:in_h-480" output.mp4

Overlay Filter

bash
# Overlay image at specified position
ffmpeg -i video.mp4 -i logo.png -filter_complex "overlay=10:10" output.mp4

# Overlay at bottom-right
ffmpeg -i video.mp4 -i logo.png -filter_complex "overlay=W-w-10:H-h-10" output.mp4

# Overlay at center
ffmpeg -i video.mp4 -i logo.png -filter_complex "overlay=(W-w)/2:(H-h)/2" output.mp4

Transpose Filter

bash
# Rotate 90 degrees clockwise
ffmpeg -i input.mp4 -vf "transpose=1" output.mp4

# Rotate 90 degrees counter-clockwise
ffmpeg -i input.mp4 -vf "transpose=2" output.mp4

# Rotate 180 degrees
ffmpeg -i input.mp4 -vf "transpose=1,transpose=1" output.mp4

Drawtext Filter

bash
# Add simple text
ffmpeg -i input.mp4 -vf "drawtext=text='Hello World':fontcolor=white:fontsize=24:x=10:y=10" output.mp4

# Add text with shadow
ffmpeg -i input.mp4 -vf "drawtext=text='Hello':fontcolor=white:fontsize=32:x=10:y=10:shadowcolor=black:shadowx=2:shadowy=2" output.mp4

# Add dynamic text (timestamp)
ffmpeg -i input.mp4 -vf "drawtext=text='%{pts\:hms}':fontcolor=white:fontsize=24:x=10:y=10" output.mp4

Gblur Filter

bash
# Gaussian blur
ffmpeg -i input.mp4 -vf "gblur=sigma=2" output.mp4

# Strong blur
ffmpeg -i input.mp4 -vf "gblur=sigma=5" output.mp4

Unsharp Filter

bash
# Sharpen
ffmpeg -i input.mp4 -vf "unsharp=5:5:1.0:5:5:0.0" output.mp4

# Slight sharpen
ffmpeg -i input.mp4 -vf "unsharp=3:3:0.5:3:3:0.0" output.mp4

Common Audio Filters

Volume Filter

bash
# Adjust volume (1.0 is original volume)
ffmpeg -i input.mp4 -af "volume=0.5" output.mp4

# Boost volume
ffmpeg -i input.mp4 -af "volume=2.0" output.mp4

# Use decibels
ffmpeg -i input.mp4 -af "volume=3dB" output.mp4

Afade Filter

bash
# Fade in for 3 seconds
ffmpeg -i input.mp4 -af "afade=t=in:st=0:d=3" output.mp4

# Fade out for 3 seconds
ffmpeg -i input.mp4 -af "afade=t=out:st=5:d=3" output.mp4

Amix Filter

bash
# Mix two audio tracks
ffmpeg -i audio1.mp3 -i audio2.mp3 -filter_complex "amix=inputs=2:duration=first" output.mp3

# Mix three audio tracks
ffmpeg -i audio1.mp3 -i audio2.mp3 -i audio3.mp3 -filter_complex "amix=inputs=3:duration=longest" output.mp3

Adelay Filter

bash
# Delay audio by 500 milliseconds
ffmpeg -i input.mp4 -af "adelay=500|500" output.mp4

# Different delay for left and right channels
ffmpeg -i input.mp4 -af "adelay=500|1000" output.mp4

Complex Filter Examples

Picture-in-Picture Effect

bash
ffmpeg -i main.mp4 -i pip.mp4 -filter_complex \
  "[1:v]scale=320:240[pip];[0:v][pip]overlay=10:10" \
  output.mp4

Multi-Screen Splicing

bash
ffmpeg -i video1.mp4 -i video2.mp4 -i video3.mp4 -i video4.mp4 \
  -filter_complex \
  "[0:v]scale=640:360[v0];[1:v]scale=640:360[v1];[2:v]scale=640:360[v2];[3:v]scale=640:360[v3]; \
   [v0][v1]hstack[top];[v2][v3]hstack[bottom];[top][bottom]vstack" \
  output.mp4

Video Speed Up/Down

bash
# Speed up 2x
ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4

# Slow down 0.5x
ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]" -map "[v]" -map "[a]" output.mp4

Filter Performance Optimization

Use Hardware Acceleration

bash
# Use GPU accelerated filter
ffmpeg -hwaccel cuda -i input.mp4 -vf "scale_npp=1280:720" output.mp4

Preprocessing Optimization

bash
# Crop first then scale (reduce processing pixels)
ffmpeg -i input.mp4 -vf "crop=640:480,scale=320:240" output.mp4

Filter is one of the most powerful features of FFmpeg. Mastering the use of filters allows for fine-grained control over audio and video.