$2a

Precise trim (re-encode around keyframes)

ffmpeg -ss 00:01:00 -i input.mp4 -t 90 -c:v libx264 -crf 18 -c:a aac out.mp4

## Transcode

H.264 web-safe (pix_fmt ensures broad player compatibility)

ffmpeg -i input.mp4 -c:v libx264 -crf 23 -preset slow \

-pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart out.mp4

H.265 (smaller files)

ffmpeg -i input.mp4 -c:v libx265 -crf 28 -preset slow \

-pix_fmt yuv420p -c:a aac -b:a 128k out.mp4

VP9 for web

ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 33 -b:v 0 \

-c:a libopus -b:a 128k out.webm

AV1 (best compression)

ffmpeg -i input.mp4 -c:v libaom-av1 -crf 35 -cpu-used 4 \

-c:a libopus -b:a 128k out.mkv

See `references/CODECS.md` for full codec comparison.

## Concatenate Files

Using helper script

scripts/concat.sh out.mp4 clip1.mp4 clip2.mp4 clip3.mp4

Manual concat demuxer

printf "file 'a.mp4'\nfile 'b.mp4'\n" > list.txt

ffmpeg -f concat -safe 0 -i list.txt -c copy out.mp4

## Scale / Resize

Scale to 1920×1080, keep aspect ratio, pad to fill

ffmpeg -i in.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,\

pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black" out.mp4

Scale by width only (auto height)

ffmpeg -i in.mp4 -vf "scale=1280:-2" out.mp4

## Crop

Crop 640×360 starting at (100,50)

ffmpeg -i in.mp4 -vf "crop=640:360:100:50" out.mp4

Center crop to 1:1 square

ffmpeg -i in.mp4 -vf "crop=min(iw\,ih):min(iw\,ih)" out.mp4

## Overlay / Watermark

Overlay image (top-right, 10px margin)

ffmpeg -i video.mp4 -i logo.png \

-filter_complex "[0:v][1:v] overlay=W-w-10:10" out.mp4

PiP: small video on top of main

ffmpeg -i main.mp4 -i pip.mp4 \

-filter_complex "[1:v]scale=320:-2[small];[0:v][small]overlay=W-w-10:H-h-10" out.mp4

## Draw Text / Titles

ffmpeg -i in.mp4 -vf \

"drawtext=text='My Title':fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf\

:fontsize=48:fontcolor=white:x=(w-text_w)/2:y=(h-text_h)/2\

:shadowx=2:shadowy=2" out.mp4

## Burn Subtitles

SRT subtitles (re-encode required)

ffmpeg -i video.mp4 -vf "subtitles=subs.srt" out.mp4

ASS/SSA subtitles (preserves styling)

ffmpeg -i video.mp4 -vf "ass=subs.ass" out.mp4

## Speed Change

2× speed (video + audio)

ffmpeg -i in.mp4 -vf "setpts=0.5*PTS" -af "atempo=2.0" out.mp4

0.5× speed (half speed)

ffmpeg -i in.mp4 -vf "setpts=2.0*PTS" -af "atempo=0.5" out.mp4

>4×: chain atempo (max 2.0 per filter)

ffmpeg -i in.mp4 -vf "setpts=0.25*PTS" -af "atempo=2.0,atempo=2.0" out.mp4

<0.5×: chain atempo (min 0.5 per filter)

ffmpeg -i in.mp4 -vf "setpts=4.0*PTS" -af "atempo=0.5,atempo=0.5" out.mp4

## Reverse

ffmpeg -i in.mp4 -vf "reverse" -af "areverse" out.mp4

## Transitions (xfade)

Dissolve between two clips (1s overlap at t=5)

ffmpeg -i a.mp4 -i b.mp4 \

-filter_complex "[0:v][1:v]xfade=transition=dissolve:duration=1:offset=5[v];\

[0:a][1:a]acrossfade=d=1[a]" \

-map "[v]" -map "[a]" out.mp4

See `references/TRANSITIONS.md` for all 40+ xfade transition types.

## Audio: Volume & Normalization

Adjust volume

ffmpeg -i in.mp4 -af "volume=1.5" out.mp4

EBU R128 normalization (two-pass)

scripts/normalize-audio.sh in.mp4 out.mp4

One-pass loudnorm

ffmpeg -i in.mp4 -af "loudnorm=I=-16:TP=-1.5:LRA=11" out.mp4

## Audio: Fade In/Out

Fade in 2s at start, fade out 3s before end (total 60s)

ffmpeg -i in.mp4 -af "afade=t=in:d=2,afade=t=out:st=57:d=3" out.mp4

## Mix / Combine Audio

Mix two audio streams

ffmpeg -i video.mp4 -i music.mp3 \

-filter_complex "[0:a][1:a]amix=inputs=2:duration=first:weights=1 0.3[a]" \

-map 0:v -map "[a]" -c:v copy out.mp4

## Color Grading

Brightness/Contrast/Saturation

ffmpeg -i in.mp4 -vf "eq=brightness=0.05:contrast=1.2:saturation=1.3" out.mp4

Hue shift

ffmpeg -i in.mp4 -vf "hue=h=30:s=1.1" out.mp4

Apply 3D LUT (.cube)

ffmpeg -i in.mp4 -vf "lut3d=file=lut.cube" out.mp4

Apply Hald CLUT PNG

ffmpeg -i in.mp4 -i lut.png \

-filter_complex "[0:v][1:v]haldclut" out.mp4

## Chroma Key / Green Screen

chromakey (color + similarity + blend)

ffmpeg -i foreground.mp4 -i background.mp4 \

-filter_complex "[0:v]chromakey=0x00FF00:0.3:0.2[fg];\

[1:v][fg]overlay" out.mp4

colorkey (simpler, exact color)

ffmpeg -i in.mp4 -vf "colorkey=green:0.3:0.2" out.mp4

## Frame Rate Conversion

Convert to 30fps

ffmpeg -i in.mp4 -vf "fps=30" out.mp4

Use motion interpolation (minterpolate)

ffmpeg -i in.mp4 -vf "minterpolate=fps=60:mi_mode=mci" out.mp4

## Extract Frames / Create Slideshow

Extract one frame per second as PNG

ffmpeg -i in.mp4 -vf "fps=1" frames/%04d.png

Slideshow from images (3s per image, 30fps output)

ffmpeg -framerate 1/3 -i frames/%04d.png -c:v libx264 -r 30 out.mp4

## Stacking / Grid Layout

Side by side (hstack)

ffmpeg -i a.mp4 -i b.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2" out.mp4

Top-bottom (vstack)

ffmpeg -i a.mp4 -i b.mp4 -filter_complex "[0:v][1:v]vstack=inputs=2" out.mp4

2×2 grid (xstack)

ffmpeg -i a.mp4 -i b.mp4 -i c.mp4 -i d.mp4 \

-filter_complex "[0:v][1:v][2:v][3:v]xstack=inputs=4:layout=0_0|w0_0|0_h0|w0_h0" out.mp4

## Hardware-Accelerated Encoding

NVIDIA NVENC H.264

ffmpeg -hwaccel cuda -i in.mp4 -c:v h264_nvenc -preset p4 -cq 23 out.mp4

Apple VideoToolbox H.265

ffmpeg -i in.mp4 -c:v hevc_videotoolbox -q:v 60 out.mp4

Intel QuickSync H.264

ffmpeg -hwaccel qsv -i in.mp4 -c:v h264_qsv -global_quality 23 out.mp4

See `references/HARDWARE-ACCEL.md` for full GPU encoding guide.

## Encoding Presets (assets/preset-profiles.json)

When the task maps to a named use case below, read `assets/preset-profiles.json`
and use the `example` field as the ready-made ffmpeg command.

Profile
Codec
CRF
Use Case

web-optimized
H.264
23
Browser streaming

high-quality
H.264
18
Archive / master

social-media-vertical
H.264
23
9:16 TikTok/Reels

social-media-square
H.264
23
1:1 Instagram

fast-preview
H.264
28
Proxy / review

lossless-intermediate
FFV1
—
Post-production store

## Multi-Stream Filter Graph Pattern

ffmpeg \

-i input_video.mp4 \

-i overlay.png \

-i audio_bed.mp3 \

-filter_complex "

[0:v]scale=1920:1080,setsar=1[base];

[1:v]scale=200:-2,format=rgba,colorchannelmixer=aa=0.8[logo];

[base][logo]overlay=W-w-20:20[composited];

[0:a][2:a]amix=inputs=2:weights=1 0.2[audio_mix]

" \

-map "[composited]" -map "[audio_mix]" \

-c:v libx264 -crf 18 -preset slow \

-c:a aac -b:a 192k \

-movflags +faststart \

output.mp4

## Common Options Reference

Flag
Meaning

`-ss`
Seek/start time (before `-i` = fast seek)

`-to`
End time (absolute)

`-t`
Duration

`-c copy`
Stream copy (no re-encode)

`-crf`
Constant Rate Factor (lower = better)

`-preset`
Encoder speed/quality tradeoff

`-movflags +faststart`
Move moov atom to front (web streaming)

`-vf`
Video filter chain

`-af`
Audio filter chain

`-filter_complex`
Multi-input/output filter graph

`-map`
Select output streams explicitly

`-an`
Drop audio

`-vn`
Drop video

`-y`
Overwrite output without prompt

## Debugging Tips

Dry-run: print filter graph without encoding

ffmpeg -i in.mp4 -vf "scale=1280:-2" -f null -

Benchmark encode speed

ffmpeg -benchmark -i in.mp4 -c:v libx264 -f null -

Show available encoders

ffmpeg -encoders | grep -E "^.V|^.A"

Show filter options

ffmpeg -help filter=loudnorm