Dark's caption embedding script

cc.png

embed-captions.sh

#!/usr/bin/env bash
set -euo pipefail

if [ $# -eq 0 ]; then
  echo "This script takes two mandatory options - \$1 is the input video, \$2 is the
  input subtitles."
  echo
  echo "By default, we burn in hard subs; you may use --soft-subs to embed soft
  subs. See: https://en.wikipedia.org/wiki/Subtitle_(captioning)#Types"

  # Note: mkv would allow default subs on (`-disposition:s:s:0 forced`), but mkv
  # doesn't work out of box in Quicktime
  exit 0
fi

###############################
# verify correct getopt version
#
# this assumes you're using gnu's getopt, which is not the same as osx' default
# getopt
###############################
# If we've got brew installed, use its gnu-getopt
if [ -x "$(command -v brew)" ]; then
    if ( ! brew list gnu-getopt ); then
        echo "You need to install gnu-getopt:"
        echo "  brew install gnu-getopt"
        exit 1
    fi

    brew_prefix=$(brew --prefix gnu-getopt)
    export PATH=${brew_prefix}/bin:$PATH
fi

set +e
opt=$(getopt -T)
set -e
# 4 is the return code from gnu's `getopt -T`, and the -n $opt checks that its
# stdout is empty, not '--' (it will be '--' if using the non-gnu osx getopt
if (( $? != 4 )) && [[ -n $opt ]]; then
    echo "Either no getopt is installed, or you're using a non-gnu getopt."
    echo "If you're on OS X, you can install gnu-getopt using homebrew to fix
    this."
    exit 1
fi
##############################
# end verifying correct getopt
##############################

OPTS=$(getopt --options s --longoptions soft-subs "$@")
eval set -- "$OPTS"

SOFTSUBS=0
while true ; do
  case "$1" in
    --soft-subs|-s)
      SOFTSUBS=1
      shift
      ;;
    --)
      shift
      break
      ;;
    *)
      echo "Unknown option: $1"
      exit 1
      ;;
  esac
done

INVIDEO=$1
INSUBS=$2
CCOVERLAY=$(dirname "$0")/cc.png

if ( ! command -v ffmpeg ); then
  echo "This script depends on ffmpeg."
  exit 1
fi

if [[ "$INVIDEO" == "" ]]; then
  echo "No in video (foo.mp4?) provided."
  echo
  exit 1
fi

if ! [[ "$INSUBS" =~ .srt$ ]]; then
  echo "No subtitles provided."
  echo
  echo "Debug: options given: INVIDEO: ${INVIDEO}, INSUBS: ${INSUBS}"
  exit 1
fi

if (( "$SOFTSUBS" )); then
  # if this file needs scaling at some point, use imagemagick:
  # convert cc.png -resize 120x120 cc.png
  if [[ ! -f $CCOVERLAY ]]; then
    echo "No ccoverlay image found."
    exit 1
  fi
fi

tmpfile=$(mktemp /tmp/postprocess-video.XXXXXX.mp4)
rm "$tmpfile" # so ffmpeg doesn't ask if you want to overwrite it

set -x
if (( "$SOFTSUBS" )); then
  # Add CCOVERLAY watermark in bottom right corner
  ffmpeg -i "$INVIDEO" \
    -vf "movie=${CCOVERLAY} [watermark]; [in][watermark] overlay=(main_w-overlay_w-10):(main_h-overlay_h-10) [out]" \
    "$tmpfile"
else
  ffmpeg -i "$INVIDEO" -vf subtitles="$INSUBS" "$tmpfile"
fi


ffmpeg -i "$tmpfile" -f srt -i "$INSUBS" \
  -c:v copy -c:a copy -c:s mov_text \
  -metadata:s:s:0 language=English \
  out.mp4

# could put this in a signal handler if you wanted to be really sure it gets
# cleaned up
rm "$tmpfile"

if (( "$SOFTSUBS" )); then
  echo "Done, with soft subs! See out.mp4"
else
  echo "Done, with hard and soft subs! See out.mp4"
fi

If you are not a regular bash user, this is the format for the CLI:

./captioning.sh video.mp4 subs.srt

If you are receiving the wrong outputs for $1 and $2 (check using echo) chances are it is an issue with getopt.

1. Install gnu-getopt via homebrew (brew install gnu-getopt).
2. Run with this prefix: PATH=/usr/local/opt/gnu-getopt/bin:$PATH ./embed-captions.sh video.mp4 subs.srt