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cknd/ffmpeg calls Last active March 25, 2025 17:30 Show Gist options

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# pack a bunch of images into a nice-looking gif running at 5 fps (with rescaling and a proper color palette)

ffmpeg -f image2 -r 5 -i %*.png -vf "scale=450:-1,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" out.gif

# convert section of video to gif (with palette, rescale and slowdown)

ffmpeg -ss 00:00:43 -to 00:00:49.5 -i input.mp4 -r 15 -vf "scale=300:-1,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse,setpts=2.0*PTS" out.gif

# shrink a video (half the size and _slightly_ lower quality)

ffmpeg -i input.mp4 -vf scale="iw/2:ih/2" -crf 30 output.mp4

Raw multi_ffmpeg.sh This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters Show hidden characters

#!/usr/bin/env bash

# Re-compress a whole folder of videos to some maximum size

#

# Usage:

# ./multi_ffmpeg.sh /path/to/folder/of/videos

#

# Output is written to new folder /path/to/folder/of/videos_encoded

#

set -e

MAX_PIXELS=1440 # max pixels on the longest side of the video. larger videos will be shrunk, smaller ones stay small.

CRF=22 # bigger number = more compression. https://trac.ffmpeg.org/wiki/Encode/H.264#a1.ChooseaCRFvalue

INPUT_DIR="$1"

[ -z "$INPUT_DIR" ] && { echo "Usage: $0 /path/to/folder"; exit 1; }

OUTPUT_DIR="${INPUT_DIR}_encoded"

mkdir -p "$OUTPUT_DIR"

for file in "$INPUT_DIR"/*; do

[ -f "$file" ] || continue

base="$(basename "$file")"

base_no_ext="${base%.*}"

out="$OUTPUT_DIR/${base_no_ext}.mp4"

echo "Processing $file -> $out"

# re-encode with

# - scale of the largest side <= MAX_PIXELS

# - pixel format yuv420p because not every player understands yuv444

# - something something for audio

ffmpeg -i "$file" \

-vf "scale='if(gte(iw,ih),min(iw,$MAX_PIXELS),-2)':'if(gte(ih,iw),min(ih,$MAX_PIXELS),-2)'" \

-c:v libx264 \

-pix_fmt yuv420p \

-crf $CRF \

-c:a aac -b:a 128k \

-y "$out"

done

echo "All done! Encoded files are in: $OUTPUT_DIR"

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