How to extract frames from all videos in a folder using ffmpeg

Question

I'm currently able to extract images from a file using the following line

ffmpeg -i inputfile.avi -r 1 image-%d.jpeg

However, I want to apply this to all the files in a folder, and place it in an output folder.

Suppose I have the current folder holding all videos:

input-videos/

----subfolder1/

------video.avi

----subfolder2/

------video.avi

I want everything in the output folder:

output/

----subfolder1/

------video/

----------*.jpeg

----subfolder2/

------video/

----------*.jpeg

What is the simplest way to go about this using a bash script? (or something else better)

Answer 1

If the folder depth is constant, the file extension is always avi and the top folders are called "input-videos" and "output":

#!/bin/bash
for file in input-videos/*/*.avi; do
    destination="output${file:12:${#file}-17}";
    mkdir -p "$destination";
    ffmpeg -i "$file" -r 1 "$destination/image-%d.jpeg";
done

If the top folders are just called anything and can be anywhere and the file extension is different, here's a script that you can call like ./script.sh <input folder> <output folder> <file extension>:

#!/bin/bash
if [ "$1" == '' ] || [ "$2" == '' ] || [ "$3" == '' ]; then
    echo "Usage: $0 <input folder> <output folder> <file extension>";
    exit;
fi
for file in "$1"/*/*."$3"; do
    destination="$2${file:${#1}:${#file}-${#1}-${#3}-1}";
    mkdir -p "$destination";
    ffmpeg -i "$file" -r 1 "$destination/image-%d.jpeg";
done