QR code video encoder / decoder

qrv

#!/bin/sh -e

# preflight & usage
CMD="$1"
FILE="$2"
[ -z "$CMD" ] || [ -z "$FILE" ] && {
  cat >&2 <<EOF
usage: $(basename "$0") encode FILE
       $(basename "$0") decode FILE
EOF
  exit 1
}

# command check
case "$CMD" in
  encode)
    FILE_OUT="$FILE.webm"
    ;;
  decode)
    FILE_OUT="$(dirname "$FILE")/recreated-$(basename "${FILE%.*}")"
    ;;
  *)
    echo "[-] Command \"$CMD\" is invalid" >&2
    exit 1
    ;;
esac
FILE_OUT_BASE="$(basename "$FILE_OUT")"

# set default configuration
[ -z "$CHUNK_PREFIX" ] && CHUNK_PREFIX='chunk'
[ -z "$CHUNK_SIZE" ] && CHUNK_SIZE=512
[ -z "$DOT_PIXEL" ] && DOT_PIXEL=8

# calculate chunk length
FILE_SIZE="$(stat --printf='%s' "$FILE")"
CHUNKS=$(((FILE_SIZE - 1) / CHUNK_SIZE + 1))
CHUNK_SUFFIX_LEN="${#CHUNKS}"

# create temporary for processing
TMP_DIR="$(mktemp -u)"
mkdir -p "$TMP_DIR"

# setup trap
cleanup() { echo "[+] cleaning up..." >&2; rm -rf "$TMP_DIR"; }
trap cleanup HUP INT QUIT ABRT

# encode
[ "$CMD" = 'encode' ] && {
  echo "[+] Splitting file..."
  split --suffix-length="$CHUNK_SUFFIX_LEN" \
        --numeric-suffixes=1 \
        --bytes="$CHUNK_SIZE" \
        "$FILE" \
        "${TMP_DIR}/${CHUNK_PREFIX}-"
  
  echo "[+] Generating QR codes..."
  for CHUNK in "${TMP_DIR}/${CHUNK_PREFIX}"-*; do
    echo "  [+] Generating QR code for ${CHUNK}"
    qrencode --8bit \
             --size="$DOT_PIXEL" \
             --read-from="$CHUNK" \
             --output="${CHUNK}.png"
  done
  
  echo "[+] Creating video..."
  ffmpeg -loglevel 16 \
         -i "${TMP_DIR}/${CHUNK_PREFIX}-%0${CHUNK_SUFFIX_LEN}d.png" \
         "${TMP_DIR}/${FILE_OUT_BASE}"

  # set output file as FILE chunks for decode test
  ORIGINAL_FILE="$FILE"
  FILE="${TMP_DIR}/${FILE_OUT_BASE}"
  FILE_OUT_BASE="$(basename "$ORIGINAL_FILE")"

  # clean up
  rm -f "${TMP_DIR}/${CHUNK_PREFIX}"-*
}

# decode / decode test
[ "$CMD" = 'decode' ] || [ "$CMD" = 'encode' ] && {
  echo "[+] Extract QR codes from the video..."
  ffmpeg -loglevel 16 \
         -i "$FILE" \
         "${TMP_DIR}/${CHUNK_PREFIX}-%0${CHUNK_SUFFIX_LEN}d.png" 
  
  echo "[+] Scanning QR codes..."
  for QRCODE in "${TMP_DIR}/${CHUNK_PREFIX}"-*.png; do
    echo "  [+] Scanning QR code for ${QRCODE}"
    zbarimg --quiet \
            --raw "$QRCODE" \
        | iconv --from=UTF-8 \
                --to=ISO-8859-1 \
        | head --bytes="$((CHUNK_SIZE + 1))" \
        | head --bytes=-1 >"${QRCODE}.bin"
  done
  
  echo "[+] Rebuilding file..."
  cat "${TMP_DIR}/${CHUNK_PREFIX}"-*.png.bin > "${TMP_DIR}/${FILE_OUT_BASE}"

  # clean up
  rm -f "${TMP_DIR}/${CHUNK_PREFIX}"-*

  # for decode, move recreated file back directly
  [ "$CMD" = 'decode' ] && mv "${TMP_DIR}/${FILE_OUT_BASE}" "${FILE_OUT}"
}

# compare and save video
[ "$CMD" = 'encode' ] && {
  echo "[+] Comparing outputs..."
  RECREATED_FILE="${TMP_DIR}/${FILE_OUT_BASE}"
  cmp "$RECREATED_FILE" "$ORIGINAL_FILE" || {
    echo "[-] Error: created file and original file are different!"
    exit 1
  }

  echo "[+] Saving video..."
  mv "$FILE" "$FILE_OUT"
}

cleanup
echo "[+] Done."