Extract Frames from a video. Useful to extract presentation slides and key moments.

extract-key-frames

#!/bin/bash -e
# Extract Key Frames from a video and print timestamp on each frame (works with ffmpeg version 5.1.2)
#
# Credits:
# - https://jdhao.github.io/2021/12/25/ffmpeg-extract-key-frame-video/
# - https://superuser.com/questions/575854/can-ffmpeg-extract-images-from-a-video-with-timestamps
#
# First parameter: input video
# Second parameter: output directory
# Example ./extract-key-frames myvideo.mp4 outdir/
#
# Info about: select='gt(scene,0.01)'
#  The value for scene is between 0 and 1, which measures the pixel level difference between 
#  current frame and previous frame. We can tweak this value to generate different number of 
#  output images. Intuitively, the smaller the value, the larger number of images we will
#  extract. Typically, a value of 0.3 or 0.4 may be enough.

if [ ! -d "$2" ]
then
    echo "Creating $2 ..."
    mkdir -p "$2"
fi

ffmpeg -i "$1" -vf "select='gt(scene,0.01)', drawtext=fontfile=/usr/share/fonts/TTF/Vera.ttf: text='%{pts\:hms}': x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -vsync vfr "$2/frame-%2d.jpg"