crookm

mkdir dash && \
ffmpeg -hide_banner -i original.mkv -c:v libvpx-vp9 -row-mt 1 -keyint_min 150 -g 150 -tile-columns 4 -frame-parallel 1 \
-movflags faststart -f webm -dash 1 -speed 3 -threads 4 -an -vf scale=426:240 -b:v 400k -r 30 -dash 1 dash/426x240-30-400k.webm && \
ffmpeg -hide_banner -i original.mkv -c:v libvpx-vp9 -row-mt 1 -keyint_min 150 -g 150 -tile-columns 4 -frame-parallel 1 \
-movflags faststart -f webm -dash 1 -speed 3 -threads 4 -an -vf scale=426:240 -b:v 600k -r 30 -dash 1 dash/426x240-30-600k.webm && \
ffmpeg -hide_banner -i original.mkv -c:v libvpx-vp9 -row-mt 1 -keyint_min 150 -g 150 -tile-columns 4 -frame-parallel 1 \
-movflags faststart -f webm -dash 1 -speed 3 -threads 4 -an -vf scale=640:360 -b:v 700k -r 30 -dash 1 dash/640x360-30-700k.webm && \
ffmpeg -hide_banner -i original.mkv -c:v libvpx-vp9 -row-mt 1 -keyint_min 150 -g 150 -tile-columns 4 -frame-parallel 1 \
-movflags faststart -f webm -dash 1 -speed 3 -threads 4 -an -vf scale=640:360 -b:v 900k -r 30 -dash 1 dash/640x360-30-900k.we

crookm

#!/bin/bash

task() {
  sleep 1; echo "$1 - $(date)";
}

N=2

for item in {1..6}; do
  ((i=i%N)); ((i++==0)) && wait