Fix vertical video by placing a blurred image in the background. This script accepts a width/height for resizing.

devert

#!/usr/bin/env sh
# original from http://stackoverflow.com/a/30819570/187663
if [ $# -lt 2 ]
then
        echo "Usage: devert {input video filename} {input image filename}"
        echo "Usage: devert {input video filename} {input image filename} {width} {height}"
        echo ""
        echo "Excluding the width and height will generate a video at 1280x720"
        exit;
fi
inputvideo=$1
inputimage=$2
width=${3:=1280}
height=${4:=720}
ffmpeg -i $inputvideo -i $inputimage -filter_complex "[0:v]scale=-1:$height[scaled_video];[1:v]scale=$width:$height,boxblur=16[blur_image];[blur_image][scaled_video]overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2[outv]" -c:v libx264 -aspect $width/$height -map [outv] -map 0:a -c:a copy $inputvideo.landscape.mp4