timelapse

#!/bin/sh

# usage: timelapse <inputvid> <outputvid> <N>
# where <N> is a number with which the video will speed up by 2^(N+1)

set -x
set -e
input=$1
output=$2
tmp=`mktemp -d`

avg="tblend=average,framestep=2"
times=${3:-4}
speed=2
for i in $(seq $times); do
  avg="$avg,tblend=average,framestep=2"
  speed=$(($speed * 2))
done
ffmpeg -i "$input" -vf "$avg,setpts=PTS/$speed" -r 60 -an "$output"


## OTHER IDEA

#speedup=${3:-20}
#blurdef=$(($speedup * 5))
#blur=${4:-$blurdef}
#ffmpeg -i $input -filter:v "tmix=frames=$blur,select='not(mod(n\,$blur))',setpts=PTS/$speedup" -an $output
# ffmpeg -i $tmp/first.mp4  -filter:v "setpts=PTS/$speedup" -an -r 60 $output

## DIDNT TRY

#ffmpeg -i $input -vf minterpolate=fps=1/$speedup $output
# tries=${3:-6}
# last=$input
# for i in $(seq $tries); do
#   next=$tmp/$i.mp4
#   ffmpeg -i $last -filter:v "tmix=frames=4:weights=1" -an -r 60 $tmp/tmp.mp4
#   ffmpeg -i $tmp/tmp.mp4 -filter:v "setpts=PTS/2" -an -r 60 $next
#   rm $tmp/tmp.mp4
#   echo $next
# done
# cp $next $output