combine-clips

#!/bin/sh

#===============================================================================
# combine-clips
# combine an image or video file with an audio clip
#===============================================================================

# dependencies:
# ffmpeg file grep

#===============================================================================
# script usage
#===============================================================================

usage ()
{
# if argument passed to function echo it
[ -z "${1}" ] || echo "! ${1}"
# display help
echo "\
# combine an image or video file with an audio clip

$(basename "$0") -i input.(mp4|mkv|mov|m4v|png|jpg) -a audio.(m4a|aac|wav|mp3) -o output.mp4
-i input.(mp4|mkv|mov|m4v|png|jpg)
-a audio.(m4a|aac|wav|mp3)
-o output.mp4 : optional argument # if option not provided defaults to input-name-combined-date-time"
exit 2
}


#===============================================================================
# error messages
#===============================================================================

INVALID_OPT_ERR='Invalid option:'
REQ_ARG_ERR='requires an argument'
WRONG_ARGS_ERR='wrong number of arguments passed to script'
NOT_MEDIA_FILE_ERR='is not a media file'


#===============================================================================
# check the number of arguments passed to the script
#===============================================================================

[ $# -gt 0 ] || usage "${WRONG_ARGS_ERR}"


#===============================================================================
# getopts check the options passed to the script
#===============================================================================

while getopts ':i:a:o:h' opt
do
  case ${opt} in
     i) infile="${OPTARG}";;
     a) audio="${OPTARG}";;
     o) outfile="${OPTARG}";;
     h) usage;;
     \?) usage "${INVALID_OPT_ERR} ${OPTARG}" 1>&2;;
     :) usage "${INVALID_OPT_ERR} ${OPTARG} ${REQ_ARG_ERR}" 1>&2;;
  esac
done
shift $((OPTIND-1))


#===============================================================================
# variables
#===============================================================================

# input, input name
infile_nopath="${infile##*/}"
infile_name="${infile_nopath%.*}"

# audio file extension
audio_ext="${audio##*.}"

# file command check input file mime type
infile_filetype="$(file --mime-type -b "${infile}")"
audio_filetype="$(file --mime-type -b "${audio}")"

# audio and video mimetypes
mov_mime='video/quicktime'
mkv_mime='video/x-matroska'
mp4_mime='video/mp4'
m4v_mime='video/x-m4v'
aac_mime='audio/x-hx-aac-adts'
m4a_mime='audio/mp4'

# the file command wrongly identifies .m4a audio as a video file
# so we check if the file extension is .m4a and set the mime type to audio/mp4
if [ "${audio_ext}" = 'm4a' ]; then
    audio_filetype="${m4a_mime}"
fi

# image mimetypes
png_mime='image/png'
jpg_mime='image/jpeg'

# defaults for variables
outfile_default="${infile_name}-combined-$(date +"%Y-%m-%d-%H-%M-%S").mp4"

# check if the libfdk_aac codec is installed, if not fall back to the aac codec
aac_codec="$(ffmpeg -hide_banner -stats -v panic -h encoder=libfdk_aac)"
aac_error="Codec 'libfdk_aac' is not recognized by FFmpeg."
aac_check="$(echo "${aac_codec}" | grep "${aac_error}")"

# check ffmpeg aac codecs
if [ -z "${aac_check}" ]; then
   aac='libfdk_aac' # libfdk_aac codec is installed
else
   aac='aac' # libfdk_aac codec isnt installed, fall back to aac codec
fi

#===============================================================================
# functions
#===============================================================================

# video - audio is aac, copy audio stream
record_copy () {
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${infile}" \
    -i "${audio}" \
    -shortest -fflags shortest -max_interleave_delta 100M \
    -c:a copy \
    -c:v copy \
    -map 0:0 -map 1:0 \
    -pix_fmt yuv420p \
    -movflags +faststart \
    -f mp4 \
    "${outfile:=${outfile_default}}"
}

# video - audio isnt aac, encode audio as aac
record_aac () {
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${infile}" \
    -i "${audio}" \
    -shortest -fflags shortest -max_interleave_delta 100M \
    -c:a "${aac}" \
    -c:v copy \
    -map 0:0 -map 1:0 \
    -pix_fmt yuv420p \
    -movflags +faststart \
    -f mp4 \
    "${outfile:=${outfile_default}}"
}

# image - audio is aac, copy audio stream
record_img_copy () {
  dur="$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "${audio}")"
  ffmpeg \
  -hide_banner \
  -stats -v panic \
  -framerate 1/"${dur}" \
  -i "${infile}" \
  -i "${audio}" \
  -c:a copy \
  -c:v libx264 -crf 18 -profile:v high \
  -r 30 -pix_fmt yuv420p \
  -movflags +faststart -f mp4 \
  "${outfile:=${outfile_default}}"
}

# image - audio isnt aac, encode audio as aac
record_img_aac () {
  dur="$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "${audio}")"
  ffmpeg \
  -hide_banner \
  -stats -v panic \
  -framerate 1/"${dur}" \
  -i "${infile}" \
  -i "${audio}" \
  -c:a "${aac}" \
  -c:v libx264 -crf 18 -profile:v high \
  -r 30 -pix_fmt yuv420p \
  -movflags +faststart -f mp4 \
  "${outfile:=${outfile_default}}"
}


#===============================================================================
# case statement
#===============================================================================

# run the ffmpeg function based on the audio mime type
case "${infile_filetype}" in
    "${mov_mime}"|"${mkv_mime}"|"${mp4_mime}"|"${m4v_mime}")
        if [ "${audio_filetype}" = 'audio/x-hx-aac-adts' ]; then
          # video - audio is aac, copy audio stream
          record_copy
            else
          # video - audio isnt aac, encode audio as aac
          record_aac
        fi;;
    "${png_mime}"|"${jpg_mime}")
        if [ "${audio_filetype}" = "${aac_mime}" ]; then
          # image - audio is aac, copy audio stream
          record_img_copy
            else
          # image - audio isnt aac, encode audio as aac
          record_img_aac
        fi;;
    *) usage "${infile} ${NOT_MEDIA_FILE_ERR}";;
esac