#!/bin/bash
#
# Calin-Andrei Burloiu, 2011, calin.burloiu@gmail.com
#
# This script extracts a thumbnail from a random frame of a video file.
# 
#

if test $# -ne 3; then
    echo "Usage: $0 input-video output-image resolution"
    exit 1
fi

in="$1"
out="$2"
resolution="$3"
FFMPEG=/usr/bin/ffmpeg

if test ! -f "$in"; then
    echo "Error: No such file $in"
    exit 1
fi

# Choose a random frame
str_duration=$(mediainfo --Inform="General;%Duration/String3%" "$in" | cut -d"." -f1)
h=$(echo $str_duration | cut -d":" -f1 | sed -r 's/^[0]*//')
if [ -z "$h" ]; then h=0; fi
m=$(echo $str_duration | cut -d":" -f2 | sed -r 's/^[0]*//')
if [ -z "$m" ]; then m=0; fi
s=$(echo $str_duration | cut -d":" -f3 | sed -r 's/^[0]*//')
if [ -z "$s" ]; then s=0; fi
s=$(($h * 3600 + $m * 60 + $s))

seek_point=$(echo "$s $RANDOM" | awk '{ print int($1 * $2 / 32767) }')

#"$FFMPEG" -i "$in" -ss "$seek_point" -vframes 1 -s "$resolution" -f image2 "$out"
"$FFMPEG" -ss "$seek_point" -i "$in" -vcodec mjpeg -vframes 1 -an -s "$resolution" -f rawvideo "$out"