webm-lua

#!/usr/bin/env bash

#Usage: webm [INPUT] [start time in ss.fff] [duration in s.fff] [filename] [OPTIONAL additional settings placed in quotes e.g "-vf scale:-1:360 -threads 8"]
#requires: bc, gdate, youtube-dl, ffmpeg

LENGTH=$(bc <<< "scale=3; $3-$2")
BITRATE=$(bc <<< "scale=3; 24/$LENGTH")
MAXSIZE=3145728
MINSIZE=3093299
IDEAL=3133440
sizeNOW=0
sizeOLD=0
ATTEMPTS=0
oldBR=0
TIMESTAMP=$2

if (( $(bc <<< "$TIMESTAMP < 4") )) #to prevent negative timestamps
then
    UNIT=0
    BACKSTEP=0
    NEWTIME=$2
else
    UNIT=4
    BACKSTEP=4 #backstep in seconds since epoch
    NEWTIME=$(bc <<< "$TIMESTAMP - $BACKSTEP") #timestamp shifted 4 or 0 seconds back
fi

while ([ $sizeNOW -lt $MINSIZE ] || [ $sizeNOW -gt $MAXSIZE ]) && [ $ATTEMPTS -lt 5 ]; do

    if [[ $1 == *"http"* ]]
    then
        INPUT="$(youtube-dl -f bestvideo/best -g "$1")"
    else
        INPUT="${1//\\\ /\ }"
    fi

    sizeOLD=$sizeNOW
    safetyBR=$oldBR
    oldBR=$BITRATE

    echo "ffmpeg -ss "$NEWTIME" -i "$INPUT" -ss "$UNIT" -c:v libvpx -an -sn -t "$LENGTH" -b:v "$BITRATE"M -y -v fatal -stats ~/Desktop/"$4".webm"

    ffmpeg -ss "$NEWTIME" -i "$INPUT" -ss "$UNIT" -c:v libvpx -an -sn -t "$LENGTH" -b:v "$BITRATE"M -y -v fatal -stats ~/Desktop/"$4".webm

    sizeNOW=$(wc -c <~/Desktop/"$4".webm)
    BITRATE=$(bc <<< "scale=3;($IDEAL/$sizeNOW)*$BITRATE")

    if (( $(bc <<< "$oldBR > $safetyBR") ))
    then
        INCREASING=1
    else
        INCREASING=0
    fi

    ((ATTEMPTS++))

    if (( $sizeNOW < $sizeOLD )) && (( $INCREASING == 1 )) #to avoid errors caused by bitrate being set too high
    then
        echo
        echo "#"$ATTEMPTS"    $(($sizeNOW / 1024))kB    @"$oldBR"Mb/s"
        echo "Maximum bitrate exceeded. Next @"$safetyBR"Mb/s"
        ffmpeg -ss "$NEWTIME" -i "$INPUT" -ss "$UNIT" -c:v libvpx -an -sn -t "$LENGTH" -b:v "$safetyBR"M -y -v fatal -stats ~/Desktop/"$4".webm
        sizeNOW=$(wc -c <~/Desktop/"$4".webm)
        ((ATTEMPTS++))
        echo
        echo "#"$ATTEMPTS"    $(($sizeNOW / 1024))kB    @"$safetyBR"Mb/s"
        echo "$4.webm    $(($sizeNOW / 1024))kB"
        exit
    fi

    echo
    echo "#"$ATTEMPTS"    $(($sizeNOW / 1024))kB    @"$oldBR"Mb/s"
    echo "Next @"$BITRATE"Mb/s"
done

echo
echo "$4.webm    $(($sizeNOW / 1024))kB"