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October 19, 2025 07:05
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| #!/usr/bin/env -S nix shell nixpkgs#ffmpeg-full nixpkgs#ghc --command bash | |
| # -*- mode: sh -*- | |
| VALID_ARGS=$(getopt -o s:d:b --long seek:,duration:,bias: -- "$@") | |
| if [[ $? -ne 0 ]]; then | |
| exit 1; | |
| fi | |
| eval set -- "$VALID_ARGS" | |
| while [ : ]; do | |
| case "$1" in | |
| -s | --seek) | |
| SEEK="-ss $2" | |
| shift 2 | |
| ;; | |
| -d | --duration) | |
| DUR="$2" | |
| shift 2 | |
| ;; | |
| -b | --bias) | |
| BIAS=$2 | |
| shift 2 | |
| ;; | |
| --) | |
| shift 1 | |
| break | |
| ;; | |
| esac | |
| done | |
| if [ -x "$1" ]; then | |
| echo input not supplied! | |
| exit 1 | |
| fi | |
| INPUT="$1" | |
| if [ -x "$2" ]; then | |
| echo output not supplied! | |
| exit 2 | |
| fi | |
| OUTPUT=$2 | |
| LEN= | |
| RET= | |
| if [ -n "$DUR" ]; then | |
| LEN=$(date +'%s' --utc -d "1970-01-01 0:$DUR" 2>/dev/null) | |
| RET=$? | |
| if [[ $RET -ne 0 ]]; then | |
| LEN=$(date +'%s' --utc -d "1970-01-01 0:0:$DUR" 2>/dev/null) | |
| RET=$? | |
| fi | |
| [[ $RET -ne 0 ]] && echo "can't parse duration: $DUR" && exit 3 | |
| fi | |
| if [ -x "$DUR" ]; then | |
| LEN=$(ffprobe -select_streams v:0 -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$INPUT") | |
| fi | |
| BITRATE=$( ghc -e "2^13 * 8 * 0.995 / $LEN - 64" ) | |
| if [ -x $BIAS ]; then | |
| BIAS=0 | |
| fi | |
| Y=$(ghc -e "$(cat <<EOF | |
| let x = floor $ (1 + $BIAS/10) * ($BITRATE / 4 * 15)**0.8 | |
| in (x+40) - x \`mod\` 40 | |
| EOF | |
| )") | |
| X=$(ghc -e "2 * (floor $ $Y / 9 * 8)") | |
| echo seek=$SEEK len=$LEN x=$X y=$Y bias=$BIAS $BITRATE kbps $INPUT $OUTPUT | |
| SWS_EXTRA=force_original_aspect_ratio=decrease:force_divisible_by=2 | |
| SCALE_ARGS="-vf scale='min($X,1920)':'min($Y,1080)':$SWS_EXTRA" | |
| PARAMS=undershoot-pct=1:overshoot-pct=0:rc=1:tune=0:passes=2 | |
| CODEC="libvpx-vp9 -row-mt 1 -threads 16" | |
| set -x | |
| ffmpeg ${SEEK} \ | |
| -i "${INPUT}" \ | |
| -t "${LEN}" \ | |
| -sn \ | |
| -an \ | |
| -c:v $CODEC $SCALE_ARGS -b:v "${BITRATE}k" -pass 1 \ | |
| -f null /dev/null | |
| ffmpeg $SEEK \ | |
| -i "${INPUT}" \ | |
| -t "${LEN}" \ | |
| -sn \ | |
| -c:a libopus \ | |
| -ac 2 -b:a 64k \ | |
| -c:v $CODEC $SCALE_ARGS -b:v "${BITRATE}k" -pass 2 \ | |
| -y "${OUTPUT}" |
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