CRITICAL GUIDELINES

Windows File Path Requirements

MANDATORY: Always Use Backslashes on Windows for File Paths

When using Edit or Write tools on Windows, you MUST use backslashes (\) in file paths, NOT forward slashes (/).

Quick Reference

Task	Command Pattern
Basic filter_complex	`-filter_complex "[0:v][1:v]overlay"`
Named labels	`[input]filter[output]`
Chain filters	`filter1,filter2,filter3`
Separate chains	`chain1;chain2`
Map output	`-map "[label]"`

When to Use This Skill

Use for complex filtergraph operations:

•Multi-input compositions (PiP, grids, overlays)
•Video transitions and effects
•Audio mixing and routing
•Stream splitting for multiple outputs
•GPU + CPU hybrid processing

For basic filters: use ffmpeg-fundamentals-2025 For hardware acceleration: use ffmpeg-hardware-acceleration

FFmpeg filter_complex Reference (2025)

Comprehensive guide to complex filtergraphs, multi-input compositions, and advanced filter chains.

filter_complex Syntax

Basic Structure

code

-filter_complex "filterchain1;filterchain2;..."

Each filterchain consists of:

•Input labels: [input_label]
•Filter(s): filter1,filter2,... (comma-separated)
•Output labels: [output_label]

Complete Syntax

code

[input_label1][input_label2]filter=param1=value1:param2=value2[output_label]

Syntax Components

Component	Description	Example
`[0:v]`	Video stream from input 0	First input video
`[0:a]`	Audio stream from input 0	First input audio
`[1:v]`	Video stream from input 1	Second input video
`[label]`	Custom named label	User-defined
`,`	Chain filters sequentially	`scale,fps`
`;`	Separate independent chains	`chain1;chain2`
`=`	Parameter assignment	`scale=1280:720`
`:`	Parameter separator	`w=1280:h=720`

Stream References

Reference	Meaning
`[0]`	First input (all streams)
`[0:v]`	First input, video stream
`[0:a]`	First input, audio stream
`[0:s]`	First input, subtitle stream
`[0:v:0]`	First input, first video stream
`[1:a:1]`	Second input, second audio stream

Default Labels

•Unlabeled first filter input uses in
•Unlabeled last filter output uses out
•Unlabeled pads connect sequentially

Escaping Rules

bash

# Wrap filtergraph in double quotes
ffmpeg -i input.mp4 \
  -filter_complex "[0:v]drawtext=text='Hello World':fontsize=24[out]" \
  -map "[out]" output.mp4

# Using shell variables
text="Dynamic Text"
ffmpeg -i input.mp4 \
  -filter_complex "[0:v]drawtext=text='$text':fontsize=24[out]" \
  -map "[out]" output.mp4

# Escaping special characters (colons in timestamps)
ffmpeg -i input.mp4 \
  -filter_complex "[0:v]drawtext=text='Time\: %{pts\:hms}':fontsize=24[out]" \
  -map "[out]" output.mp4

Common Composition Patterns

1. Picture-in-Picture (PiP)

bash

# Basic PiP - small video in bottom-right corner
ffmpeg -i main.mp4 -i pip.mp4 \
  -filter_complex "\
    [1:v]scale=320:240[pip];\
    [0:v][pip]overlay=W-w-10:H-h-10" \
  -c:v libx264 -c:a copy output.mp4

# PiP with border
ffmpeg -i main.mp4 -i pip.mp4 \
  -filter_complex "\
    [1:v]scale=320:240,drawbox=x=0:y=0:w=iw:h=ih:c=white:t=3[pip];\
    [0:v][pip]overlay=W-w-10:H-h-10" \
  output.mp4

# Animated PiP (moving)
ffmpeg -i main.mp4 -i pip.mp4 \
  -filter_complex "\
    [1:v]scale=320:240[pip];\
    [0:v][pip]overlay='W-w-10-sin(t)*20':'H-h-10-cos(t)*20'" \
  output.mp4

# PiP with fade-in
ffmpeg -i main.mp4 -i pip.mp4 \
  -filter_complex "\
    [1:v]scale=320:240,fade=in:st=2:d=1[pip];\
    [0:v][pip]overlay=W-w-10:H-h-10:enable='gte(t,2)'" \
  output.mp4

2. Video Grid Layouts

Using hstack/vstack (fast, simple):

bash

# 2x2 Grid
ffmpeg -i 1.mp4 -i 2.mp4 -i 3.mp4 -i 4.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=inputs=2[top];\
    [v2][v3]hstack=inputs=2[bottom];\
    [top][bottom]vstack=inputs=2[out]" \
  -map "[out]" output.mp4

# 3x2 Grid
ffmpeg -i 1.mp4 -i 2.mp4 -i 3.mp4 -i 4.mp4 -i 5.mp4 -i 6.mp4 \
  -filter_complex "\
    [0:v]scale=426:240[v0];\
    [1:v]scale=426:240[v1];\
    [2:v]scale=426:240[v2];\
    [3:v]scale=426:240[v3];\
    [4:v]scale=426:240[v4];\
    [5:v]scale=426:240[v5];\
    [v0][v1][v2]hstack=inputs=3[top];\
    [v3][v4][v5]hstack=inputs=3[bottom];\
    [top][bottom]vstack=inputs=2[out]" \
  -map "[out]" output.mp4

Using xstack (more flexible positioning):

bash

# 2x2 Grid with xstack
ffmpeg -i 1.mp4 -i 2.mp4 -i 3.mp4 -i 4.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][v2][v3]xstack=inputs=4:layout=0_0|640_0|0_360|640_360[out]" \
  -map "[out]" output.mp4

# L-shaped layout
ffmpeg -i main.mp4 -i side1.mp4 -i side2.mp4 \
  -filter_complex "\
    [0:v]scale=960:720[main];\
    [1:v]scale=320:360[s1];\
    [2:v]scale=320:360[s2];\
    [main][s1][s2]xstack=inputs=3:layout=0_0|960_0|960_360[out]" \
  -map "[out]" output.mp4

3. Video Transitions (xfade)

bash

# Simple fade transition
ffmpeg -i first.mp4 -i second.mp4 \
  -filter_complex "\
    [0:v][1:v]xfade=transition=fade:duration=1:offset=4[v];\
    [0:a][1:a]acrossfade=d=1[a]" \
  -map "[v]" -map "[a]" output.mp4

# Dissolve transition
ffmpeg -i first.mp4 -i second.mp4 \
  -filter_complex "\
    [0:v][1:v]xfade=transition=dissolve:duration=2:offset=3[v]" \
  -map "[v]" output.mp4

# Wipe transitions
ffmpeg -i first.mp4 -i second.mp4 \
  -filter_complex "[0:v][1:v]xfade=transition=wipeleft:duration=1:offset=4[v]" \
  -map "[v]" output.mp4

# Multiple transitions (3+ clips)
ffmpeg -i 1.mp4 -i 2.mp4 -i 3.mp4 \
  -filter_complex "\
    [0:v]settb=AVTB,fps=30[v0];\
    [1:v]settb=AVTB,fps=30[v1];\
    [2:v]settb=AVTB,fps=30[v2];\
    [v0][v1]xfade=transition=fade:duration=1:offset=4[xf1];\
    [xf1][v2]xfade=transition=dissolve:duration=1:offset=8[out]" \
  -map "[out]" output.mp4

Available xfade transitions:

•fade, fadeblack, fadewhite
•wipeleft, wiperight, wipeup, wipedown
•slideleft, slideright, slideup, slidedown
•circlecrop, rectcrop, distance
•radial, smoothleft, smoothright
•dissolve, pixelize, diagtl, diagtr, diagbl, diagbr
•hlslice, hrslice, vuslice, vdslice
•hblur, fadegrays, squeezev, squeezeh

4. Audio Mixing

bash

# Mix two audio tracks
ffmpeg -i video.mp4 -i music.mp3 \
  -filter_complex "\
    [0:a][1:a]amix=inputs=2:duration=first:dropout_transition=2[aout]" \
  -map 0:v -map "[aout]" output.mp4

# Mix with volume control
ffmpeg -i vocals.mp4 -i music.mp3 \
  -filter_complex "\
    [0:a]volume=1.0[v0];\
    [1:a]volume=0.3[v1];\
    [v0][v1]amix=inputs=2:duration=first[aout]" \
  -map 0:v -map "[aout]" output.mp4

# Audio with delay (ducking)
ffmpeg -i main.mp4 -i effect.mp3 \
  -filter_complex "\
    [1:a]adelay=2000|2000[delayed];\
    [0:a][delayed]amix=inputs=2:duration=first[aout]" \
  -map 0:v -map "[aout]" output.mp4

# Merge channels (stereo from two mono)
ffmpeg -i left.wav -i right.wav \
  -filter_complex "[0:a][1:a]amerge=inputs=2[aout]" \
  -map "[aout]" stereo.wav

# Audio crossfade between tracks
ffmpeg -i track1.mp3 -i track2.mp3 \
  -filter_complex "[0:a][1:a]acrossfade=d=3:c1=tri:c2=tri[out]" \
  -map "[out]" mixed.mp3

5. Text and Watermark Overlays

bash

# Static text overlay
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]drawtext=text='Watermark':\
    fontsize=48:fontcolor=white@0.8:\
    x=10:y=H-th-10[out]" \
  -map "[out]" output.mp4

# Fade-in text
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]drawtext=text='Hello':\
    fontsize=64:fontcolor=white:\
    x=(w-text_w)/2:y=(h-text_h)/2:\
    alpha='if(lt(t,1),t,1)'[out]" \
  -map "[out]" output.mp4

# Scrolling credits
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]drawtext=textfile=credits.txt:\
    fontsize=32:fontcolor=white:\
    x=(w-text_w)/2:y=h-t*50[out]" \
  -map "[out]" output.mp4

# Timed text (appear/disappear)
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]drawtext=text='Show at 2s':\
    fontsize=48:fontcolor=yellow:\
    x=100:y=100:\
    enable='between(t,2,5)'[out]" \
  -map "[out]" output.mp4

# Logo/image watermark
ffmpeg -i video.mp4 -i logo.png \
  -filter_complex "\
    [1:v]scale=150:-1[logo];\
    [0:v][logo]overlay=W-w-20:20[out]" \
  -map "[out]" -map 0:a output.mp4

6. Stream Splitting and Multiple Outputs

bash

# Split for multiple resolutions
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]split=3[v1][v2][v3];\
    [v1]scale=1920:1080[hd];\
    [v2]scale=1280:720[sd];\
    [v3]scale=640:360[mobile]" \
  -map "[hd]" hd.mp4 \
  -map "[sd]" sd.mp4 \
  -map "[mobile]" mobile.mp4

# Split video and audio separately
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]split=2[v1][v2];\
    [0:a]asplit=2[a1][a2];\
    [v1]scale=1280:720[vout1];\
    [v2]scale=640:360[vout2]" \
  -map "[vout1]" -map "[a1]" output1.mp4 \
  -map "[vout2]" -map "[a2]" output2.mp4

7. Video Concatenation with Filters

bash

# Concatenate with format normalization
ffmpeg -i 1.mp4 -i 2.mp4 -i 3.mp4 \
  -filter_complex "\
    [0:v]scale=1920:1080,fps=30,setpts=PTS-STARTPTS[v0];\
    [1:v]scale=1920:1080,fps=30,setpts=PTS-STARTPTS[v1];\
    [2:v]scale=1920:1080,fps=30,setpts=PTS-STARTPTS[v2];\
    [0:a]aformat=sample_rates=48000:channel_layouts=stereo[a0];\
    [1:a]aformat=sample_rates=48000:channel_layouts=stereo[a1];\
    [2:a]aformat=sample_rates=48000:channel_layouts=stereo[a2];\
    [v0][a0][v1][a1][v2][a2]concat=n=3:v=1:a=1[outv][outa]" \
  -map "[outv]" -map "[outa]" output.mp4

GPU-Accelerated Filtergraphs

Full CUDA Pipeline

bash

# GPU decode -> GPU filter -> GPU encode
ffmpeg -hwaccel cuda -hwaccel_output_format cuda -i main.mp4 \
  -hwaccel cuda -hwaccel_output_format cuda -i overlay.mp4 \
  -filter_complex "\
    [0:v]scale_cuda=1920:1080[main];\
    [1:v]scale_cuda=320:180[pip];\
    [main][pip]overlay_cuda=W-w-10:H-h-10[out]" \
  -map "[out]" -map 0:a \
  -c:v h264_nvenc -preset p4 output.mp4

Hybrid GPU + CPU Pipeline

When you need CPU-only filters (drawtext, subtitles), use hwdownload/hwupload:

bash

# GPU scale -> CPU text -> GPU encode
ffmpeg -hwaccel cuda -hwaccel_output_format cuda -i input.mp4 \
  -filter_complex "\
    [0:v]scale_cuda=1920:1080[scaled];\
    [scaled]hwdownload,format=nv12[cpu];\
    [cpu]drawtext=text='Watermark':fontsize=48:x=10:y=10[text];\
    [text]hwupload_cuda[out]" \
  -map "[out]" \
  -c:v h264_nvenc output.mp4

ABR Ladder with GPU

bash

# Generate multiple resolutions on GPU
ffmpeg -y -vsync 0 \
  -hwaccel cuda \
  -hwaccel_output_format cuda \
  -i input.mp4 \
  -filter_complex "[0:v]split=3[v1][v2][v3];\
    [v1]scale_cuda=1920:1080[hd];\
    [v2]scale_cuda=1280:720[sd];\
    [v3]scale_cuda=640:360[mobile]" \
  -map "[hd]" -c:v h264_nvenc -b:v 5M output_1080p.mp4 \
  -map "[sd]" -c:v h264_nvenc -b:v 2M output_720p.mp4 \
  -map "[mobile]" -c:v h264_nvenc -b:v 500k output_360p.mp4

Advanced Patterns

Multi-Layer Composition

bash

# Video with lower third, logo, and timecode
ffmpeg -i main.mp4 -i logo.png -i lower_third.png \
  -filter_complex "\
    [1:v]scale=150:-1[logo];\
    [2:v]scale=400:-1[third];\
    [0:v][logo]overlay=W-w-20:20[step1];\
    [step1][third]overlay=50:H-h-80:enable='between(t,5,55)'[step2];\
    [step2]drawtext=text='%{pts\\:hms}':\
      fontsize=32:fontcolor=white:\
      x=W-tw-20:y=H-th-20[out]" \
  -map "[out]" -map 0:a output.mp4

Audio Visualization Overlay

bash

# Waveform overlay on video
ffmpeg -i video.mp4 -i audio.mp3 \
  -filter_complex "\
    [1:a]showwaves=s=1920x200:mode=cline:colors=white@0.8[wave];\
    [0:v][wave]overlay=0:H-h-50[out]" \
  -map "[out]" -map 1:a output.mp4

# Spectrum analyzer
ffmpeg -i video.mp4 \
  -filter_complex "\
    [0:a]showspectrum=s=1920x200:legend=0:color=rainbow[spec];\
    [0:v][spec]overlay=0:H-h[out]" \
  -map "[out]" -map 0:a output.mp4

Time-Based Effects

bash

# Different effects at different times
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]split=3[v1][v2][v3];\
    [v1]trim=0:5,setpts=PTS-STARTPTS[part1];\
    [v2]trim=5:10,setpts=PTS-STARTPTS,eq=brightness=0.2:saturation=2.0[part2];\
    [v3]trim=10,setpts=PTS-STARTPTS[part3];\
    [part1][part2][part3]concat=n=3:v=1:a=0[out]" \
  -map "[out]" -map 0:a output.mp4

Debugging Filtergraphs

Verbose Logging

bash

# Enable debug logging
ffmpeg -loglevel debug -i input.mp4 -filter_complex "..." output.mp4

# Show filter graph info
ffmpeg -filter_complex_script script.txt -lavfi "..." 2>&1 | grep -i filter

Validate Filtergraph

bash

# Test filtergraph without encoding (null output)
ffmpeg -i input.mp4 -filter_complex "..." -f null -

# Check specific filter options
ffmpeg -h filter=overlay
ffmpeg -h filter=xfade
ffmpeg -h filter=amix

Common Errors

Error	Cause	Solution
"Input pad not connected"	Missing input label	Add `[0:v]` or correct label
"Output pad not connected"	Unused filter output	Add `-map` or connect to next filter
"Stream specifier not found"	Invalid stream reference	Check input has that stream type
"Filter not found"	Missing filter in FFmpeg build	Check `ffmpeg -filters`
"Discarding frame"	Timestamp discontinuity	Add `setpts=PTS-STARTPTS`

Performance Tips

•Order matters - Put expensive filters later in the chain
•Use GPU filters when available (scale_cuda, overlay_cuda)
•Avoid unnecessary format conversions - Keep same pixel format
•Split before filters if creating multiple outputs
•Use -threads 0 to auto-detect optimal thread count

Best Practices

•Use meaningful labels - [scaled] not [v1] for clarity
•Test on short clips - Use -t 5 to test first 5 seconds
•Check all streams - Verify audio mapping with -map
•Normalize inputs - Match fps, resolution before concat/transitions
•Quote the filtergraph - Use double quotes around entire -filter_complex
•Handle audio separately - Video and audio often need different processing

This guide covers filter_complex patterns for 2025. For hardware acceleration details, see ffmpeg-hardware-acceleration. For basic filter syntax, see ffmpeg-fundamentals-2025.