Batch shrink videos with ffmpeg.

shrinkvid.zsh

# shrinkvid - batch shrink videos with ffmpeg
# Add this to your ~/.zshrc
# --------------------------------------------
# Usage:
#   shrinkvid [directory] [format] [crf]
#
# Examples:
#   shrinkvid                 # defaults: ~/Downloads, mp4, CRF=28
#   shrinkvid ~/Movies        # custom directory
#   shrinkvid . mkv 24        # current dir, mkv files, CRF=24
#
# Notes:
# - Originals are renamed with `_Original` suffix.
# - Skips files already ending in `_Original`.
# - Does not overwrite existing `_Original` files.

shrinkvid() {
  emulate -L zsh
  set -o pipefail
  setopt null_glob

  local dir="${1:-$HOME/Downloads}"
  local fmt="${2:-mp4}"
  local crf="${3:-28}"

  builtin pushd -q "$dir" || { echo "Directory not found: $dir"; return 1; }

  for i in *.${fmt}; do
    [[ "$i" == *_Original.${fmt} ]] && continue
    local original="${i%.*}_Original.${fmt}"
    mv -n -- "$i" "$original" || { echo "Skipping $i (backup exists)"; continue; }
    echo "Shrinking $i with CRF=$crf..."
    ffmpeg -y -i "$original" -vcodec libx264 -crf "$crf" "$i"
  done

  popd -q
}