#!/bin/bash
# 
# Copyright (c) 2017 Kris Occhipinti.
# http://filmsbykris.com 
#
# This program is free software: you can redistribute it and/or modify  
# it under the terms of the GNU General Public License as published by  
# the Free Software Foundation, version 3.
#
# This program is distributed in the hope that it will be useful, but 
# WITHOUT ANY WARRANTY; without even the implied warranty of 
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License 
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#

if [ $# -lt 1 ]
then
  echo "Usage: $0 <video file>"
  echo "Example: $0 'myvideo.mp4'"
  exit 1
fi

video="$1"
number=100
frames="$(ffprobe -v error -show_format -show_streams  "$video"|grep nb_frame|cut -d\= -f2)"
fs="$(echo "${frames}/100"|bc)"

echo "There are $fames frames in the file."
echo "Extracting a frame ever $fs frames to get $number frames."
sleep 1

ffmpeg -i "$video" -vf "select=not(mod(n\,$fs))" -vsync vfr -q:v 2 img_%03d.jpg