Simple script to slice mp4 into webms

#!/bin/bash

# Quantity of webms to produce for each input video
quantity=6
# Length of each webm (in seconds)
interval=10
# Whether you want audio or not
audio=true

if [[ "$audio" = true ]]; then
    audio_bitrate=96
    audio_settings="-c:a libvorbis -b:a ${audio_bitrate}K"
else
    audio_bitrate=0
    audio_settings="-an"
fi

# Change 4 to whatever file size limit you have (in MB)
video_bitrate=$(bc <<< 4*1000*8/$interval-$audio_bitrate)

for input in *.mp4; do (
    # Where to start the first webm (in seconds)
    start=0
    for (( i = 1; i <= quantity; i++ ))
    do
        ffmpeg -ss $start -i "$input" -t $interval -c:v libvpx -crf 10 -qmax 50 -b:v ${video_bitrate}K -deadline good -cpu-used 0 $audio_settings "${input%.*}_${i}.webm"
        (( start+=interval ))
    done
); done