Bash Video Thumbnailer

#!/bin/bash
# videothumbs, a simple videothumbnailer
#
#  Copyright (C) 2012 Julian Hughes julianhughes<at>gmailDOTcom
#
#  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; either version 3 of the License, or
#  (at your option) any later version.
#
#  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/>
#
# REQUIRES: mplayer, ffmpeg, imagemagick

#check mplayer, ffmpeg, imagemagick are installed
type montage >/dev/null 2>&1 || { echo >&2 "ImageMagick is not \
installed or is not in your path."; exit 1; }
type mplayer >/dev/null 2>&1 || { echo >&2 "mplayer is not installed \
or is not in your path."; exit 1; }
type ffmpeg >/dev/null 2>&1 || { echo >&2 "ffmpeg is not installed \
or is not in your path."; exit 1; }

#user options
while getopts 'o:' OPTION
do
    case $OPTION in
    o)  oflag=1
        oval=$OPTARG
        ;;
    esac
done
shift $(($OPTIND-1))

function mpscreens ()
{
mplayer "$i" -noconfig all -nolirc -nojoystick -nosound -ss 5 \
-sstep $STEP -vf scale=$WIDE:-2 -vo png:outdir=$OUT
}
function ffscreens ()
{
for t in {1..40}; do ffmpeg -ss $(($t*$STEP)) -i "$i" -f image2 \
-vframes 1  -vf scale="$WIDE":"$H" "$OUT"/$(printf "%02d\n" "$t").png
done
}

for i in "$@" ;do

FILE="${i%.*}"
FILE="${FILE##*/}"
EXT="${i##*\.}"
OUT=/tmp/thumbs
INFO="$OUT"/info

mkdir "$OUT"

#set output destination. Output dir exists and writable?
#defaults to movie directory.
if [ $oflag ]; then
    if [ ! -d "$oval" -o ! -w "$oval" ]; then
    printf "\n\n\tOutput directory is not writable or doesn't exist\n\n"
    exit
    fi
    IMGOUT=$oval/"${FILE##*/}".jpg
    else
    IMGOUT="${i%.*}".jpg
fi

#use mplayer based capture for mkv/mpg, ffmpeg for everything else
#because mplayer chokes if there is no keyframe at -ss # in avi & on
# seeking some mp4.
if [[ $EXT == !(mkv|MKV|mpg|MPG|mpeg|MPEG) ]] ; then
    SCREENS=ffscreens
    else
    SCREENS=mpscreens
fi

#dump movie info to text file
mplayer "$i" -noconfig all -identify -novideo -vo null -ao null \
-frames 0 2>/dev/null |grep AUDIO |awk -F "ID_" '{print $2}'|sort -u |\
sed '/^$/d' >"$INFO" && \
mplayer "$i" -noconfig all -identify -nosound -vo null -ao null \
-frames 0 2>/dev/null |egrep "VIDEO|LENGTH" |awk -F "ID_" '{print $2}'|\
sort -u |sed '/^$/d' >>"$INFO"

#for 4x10 images find movie length, divide by 40 for interval steps.
LENGTH=$(grep LENGTH= "$INFO"|awk -F = '{print $2}')
STEP="$(echo $LENGTH/40 |bc)"

#images should show correct aspect for anamorphic video, so find height
#and aspect ratio and calculate displayed width, rounded to integer.
A=$(grep VIDEO_ASPECT= "$INFO"  |awk -F = '{print $2}')
H=$(grep VIDEO_HEIGHT= "$INFO" |awk -F = '{print $2}')
WIDE="$(echo $A*$H |bc)"
WIDE=$(printf "%.0f\n" $WIDE)

#get basic codec and dimension info for printing title.
W=$(grep VIDEO_WIDTH= "$INFO" |awk -F = '{print $2}')
VIDEO=$(grep VIDEO_FORMAT= "$INFO" |awk -F = '{print $2}')
AUDIO=$(grep AUDIO_CODEC= "$INFO" |awk -F = '{print $2}')
CHAN=$(grep -m 1 AUDIO_NCH= "$INFO" |awk -F = '{print $2}')
TITLE="\n\n""${i##*/}""\nVideo: "$VIDEO", "$W"x"$H"\nAudio: "$AUDIO", \
"$CHAN" Channels"

#dump uncompressed png images to temp dir while redirecting overly
#verbose ffmpeg/mplayer output to /dev/null
$SCREENS>/dev/null 2>&1

#make montage, clean up, quit.
montage -mode concatenate -geometry 252x -border 1 -tile 4x \
"$OUT"/*.png -title "$TITLE" "$IMGOUT" && \
rm -rf "$OUT"

done
exit 0