Bash script to encode videos with ffmpeg to under discord's 8MiB file limit

discordencode.sh

#!/bin/bash
# discordencode - encodes a video file to under 8MiB for Discord
usage () {
    echo "Usage: [NOAUDIO=1] [VPRESET=x264-preset] discordencode input output.mp4"
}
if [ -z "$1" ]
then
    usage
    exit 1
fi
if [ -z "$2" ]
then
   usage
   exit 1
fi
if [ ! -f "$1" ]; then
    echo "$1 does not exist"
    exit 2
fi
# Bitrate math functions
# Bc and ffprobe are a bit arcane
duration_seconds () {
    ffprobe -i "$1" -show_entries format=duration -v quiet -of csv="p=0"
}

subtract_and_truncate () {
    echo "x = $1; scale = 0; x / 1 - $2" | bc -l
}

divide_floats() {
    echo "scale=2; $1 / $2" | bc
}

audioargs="-c:a aac -b:a 128k"
audiobits=128
if [[ $NOAUDIO ]] && [ "$NOAUDIO" -eq "1" ]
then
    audioargs="-an"
    audiobits=0
    echo "Using no audio"
fi
if [ -z "$VPRESET" ]
then
    VPRESET=veryslow
fi
duration=$(duration_seconds "$1")
echo $1
echo Duration is $duration
kbits=$(subtract_and_truncate $(divide_floats 45473.1 $duration) $audiobits)
echo Video bitrate is $kbits kb/s
set -x
ffmpeg -y -i "$1" -c:v libx264 -preset $VPRESET -threads 0 -b:v ${kbits}k -pass 1 -an -f mp4 /dev/null
ffmpeg -i "$1" -c:v libx264 -preset $VPRESET -threads 0 -b:v ${kbits}k -pass 2 $audioargs "$2"

Appreciate you for forking and modifying it for me!