#! /usr/bin/env nix-shell
#! nix-shell -i bash -p ffmpeg
#
# Converts a regular video into a 4x timelapse.
#
# Research:
# - https://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video
# - https://superuser.com/questions/777938/ffmpeg-convert-a-video-to-a-timelapse#778425
# - https://superuser.com/questions/803453/ffmpeg-speed-up-video-but-keep-same-quality
#
#-s hd1080 \
#    -c:v libx264 \
#    -b:v 15M \
#    -preset slow \
#    -crf 10 \

ffmpeg -i "$1" \
    -crf 10 \
    -filter:v "setpts=0.25*PTS" \
    -q 0 \
    -an "$2"