Make a thumbnail of a video using VLC and imagemagick. No real improvement over using ffmpeg except if you have VLC installed and not ffmpeg.

vlc-thumb

#!/bin/sh
# usage :
# @param source video
# @param destination

set -e
### USAGE HELPER ######
usage () {
    echo "takes a thumbnail from a video"
    echo ""
    echo "basic usage : thumbs.sh [OPTIONS] SRC DEST"
    echo "\t-h --help"
    echo "\t--size= expected output size"
    echo ""
}




### COMMAND LINE ARGS PARSING ########
while [ "$1" != "" ]; do
    PARAM=`echo $1 | awk -F= '{print $1}'`
    VALUE=`echo $1 | awk -F= '{print $2}'`
    case "$PARAM" in
        -h | --help)
            usage
            exit
            ;;
        --size)
            SIZE=$VALUE
            ;;
        *)
          echo "got param : $PARAM"
          if [ -z $SOURCE ]; then
            echo "no source"
            SOURCE=$PARAM
          elif [ -z $DEST ]; then
            DEST=$PARAM
          else
            echo "Error : too many arguments"
            usage
            exit 1
          fi
            ;;
    esac
    shift
done

if [ -z $SOURCE ] || [ -z $DEST ]; then
  echo "Error : require source and destination filenames"
  usage
  exit 1
fi

### Varibles Declaration ######
EXTENSION="jpg"
FILE=$(mktemp --suffix .$EXTENSION)
FILENAME=$(basename $FILE)
PREFIX=${FILENAME%.*}
DIRNAME=$(dirname $FILE)



cvlc $SOURCE \
--rate=1 --video-filter=scene \
--vout=dummy --run-time=0.01 \
--scene-format=$EXTENSION --scene-replace \
--scene-ratio=25 --scene-prefix=$PREFIX \
--scene-path=$DIRNAME vlc://quit

WIDTH=$(identify -format "%[fx:w]" $FILE)
HEIGHT=$(identify -format "%[fx:h]" $FILE)

START_H=$(($HEIGHT/3))
START_W=$(($WIDTH/3))

SIZE_H=$(($HEIGHT-2*$START_H))
SIZE_W=$(($WIDTH-2*$START_W))
#echo "${SIZE_W}x${SIZE_H}+${START_W}+${START_H}"
convert  -crop "${SIZE_W}x${SIZE_H}+${START_W}+0" -flip $FILE $DEST