ffcompress.zsh

ffcompress () {
  local TARGET_SIZE="$1"
  local INPUT="$2"

  if [[ -z "$TARGET_SIZE" || -z "$INPUT" ]]; then
    echo "Usage: ffcompress 10mb input.mp4"
    return 1
  fi

  # Strip non-numeric characters
  local SIZE_MB=${TARGET_SIZE//[^0-9.]/}

  # Get duration
  local DURATION=$(ffprobe -v error -show_entries format=duration \
    -of default=noprint_wrappers=1:nokey=1 "$INPUT")

  # Target slightly under requested size
  local TARGET_MB=$(echo "$SIZE_MB * 0.98" | bc)

  # Total bitrate in kbps
  local TOTAL_BITRATE=$(echo "($TARGET_MB * 8192) / $DURATION" | bc)

  # Bitrate split
  local AUDIO_BITRATE=96
  local VIDEO_BITRATE=$(echo "$TOTAL_BITRATE - $AUDIO_BITRATE" | bc)

  local OUTPUT="compressed_${INPUT:t}"

  ffmpeg -i "$INPUT" \
    -c:v libx264 -preset slow \
    -b:v "${VIDEO_BITRATE}k" \
    -maxrate "${VIDEO_BITRATE}k" \
    -bufsize "$((VIDEO_BITRATE * 2))k" \
    -c:a aac -b:a "${AUDIO_BITRATE}k" \
    "$OUTPUT"

  echo "Done → $OUTPUT"
}