easy-editing/merge

#!/usr/bin/env bash

files=$(ls | wc -l)

if [ $files -eq 1 ]; then
    cd $(ls)
fi

convert -density 300 *.pdf -resize 1440x1080! '%d'.png
count=$(ls *wav | wc -l)
files=""

for i in `seq 0 $(($count - 1))`; do
    # fade
    duration=$(sox $i.wav -n stat 2>&1 | grep Length | cut -d ':' -f 2 | tr -d '[:space:]')
    sox $i.wav faded-$i.wav fade 0:0.1 $(soxi -d $i.wav) 0:0.1
    files="$files faded-$i.wav"
    echo -e "file '$i.png'\nduration $duration" >> video-input-list.txt
done

sox $files output.wav

ffmpeg -f concat -safe 0 -i video-input-list.txt output.mp4
ffmpeg -i output.mp4 -i output.wav -c:v libx264 final.mp4