fade-clip

#!/bin/sh

#===============================================================================
# fade-clip
# fade video and audio in and out
#===============================================================================

# dependencies:
# ffmpeg bc

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

usage()
{
echo "\
# fade video and audio in and out

$(basename "$0") -i input.(mp4|mkv|mov|m4v) -d (0.[0-9]|1) -o output.mp4
-i infile.(mp4|mkv|mov|m4v)
-d (0.[0-9]|1) : optional argument # if option not provided defaults to 0.5
-o output.mp4  : optional argument # if option not provided defaults to input-name-fade-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'


#===============================================================================
# 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:d:o:h' opt
do
  case ${opt} in
     i) infile="${OPTARG}";;
     d) dur="${OPTARG}";;
     o) outfile="${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 and extension
infile_nopath="${infile##*/}"
infile_name="${infile_nopath%.*}"

# defaults for variables if not defined
outfile_default="${infile_name}-fade-$(date +"%Y-%m-%d-%H-%M-%S").mp4"
duration_default="0.5"

# 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
#===============================================================================

# ffmpeg fade video track
fade_v () {
    echo '+ Getting video duration' && \
    video_dur=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "${infile}" | cut -d\. -f1)
    vid_offset=$(echo "${video_dur}-${dur:=${duration_default}}" | bc -l)
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${infile}" \
    -filter_complex \
    " [0:v] fade=t=in:st=0:d=${dur:=${duration_default}},fade=t=out:st='${vid_offset}':d=${dur:=${duration_default}}[fv] " \
    -map "[fv]" \
    -c:v libx264 -preset fast \
    -profile:v high \
    -crf 18 -coder 1 \
    -pix_fmt yuv420p \
    -movflags +faststart \
    -f mp4 \
    "${outfile:=${outfile_default}}"
}

# fade video and audio tracks
fade_va () {
    echo '+ Getting video duration' && \
    video_dur=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "${infile}" | cut -d\. -f1)
    vid_offset=$(echo "${video_dur}-${dur:=${duration_default}}" | bc -l)
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${infile}" \
    -filter_complex \
    " [0:a] afade=t=in:st=0:d=${dur:=${duration_default}},afade=t=out:st='${vid_offset}':d=${dur:=${duration_default}}[fa]; 
      [0:v] fade=t=in:st=0:d=${dur:=${duration_default}},fade=t=out:st='${vid_offset}':d=${dur:=${duration_default}}[fv]
    " \
    -map "[fv]" -map "[fa]" \
    -c:a "${aac}" \
    -c:v libx264 -preset fast \
    -profile:v high \
    -crf 18 -coder 1 \
    -pix_fmt yuv420p \
    -movflags +faststart \
    -f mp4 \
    "${outfile:=${outfile_default}}"
}

# check if video has an audio track
audio_check="$(ffprobe -i "${infile}" -show_streams -select_streams a -loglevel error)"

# check if audio_check is null which means the video doesnt have an audio track
if [ -z "${audio_check}" ]; then
   fade_v "${infile}" # null value
else
   fade_va "${infile}" # non null value
fi