Extract frames between X and Y from an MP4 using FFMPEG

mp4_to_jpgs_frames.sh

#!/bin/bash -e

# To run:  mp4_to_jpgs_frames.sh 00000123 "generated/SpaghettiJPEGS" 5 25

if [ -z "$2" ]; then
	output_dir=generated/unlabelled_jpgs
else
	output_dir=$2
fi

mkdir -p $output_dir

if [ -z "$3" ]; then
	ffmpeg -y -i generated/mp4s/$1.mp4 -qscale:v 2 $output_dir/%5d.jpg > /dev/null 2>&1 < /dev/null
else
	startFrame=$(($3))
	endFrame=$(($4))
	#Input -1 to extract to the end of the video.  Make 10,000 a bigger number if you have longer videos.
	if (( $endFrame < 0)); then
		endFrame=10000
	fi

	#echo $startFrame
	#echo $endFrame
	#Build the select statement because putting them in the command wasn't working
	a="between(n\\,"
	b="\\,"
	c=")"
	selectStatement=${a}$startFrame${b}$endFrame${c}
	echo "Selecting "$selectStatement

	ffmpeg -y -i generated/mp4s/$1.mp4 -qscale:v 2 -vf select=$selectStatement -vsync 0 $output_dir/$1" - "%5d.jpg > /dev/null 2>&1 < /dev/null
fi

echo "Frames extracted successfully"