crossfade-clips

#!/bin/sh

# ffmpeg cross fade clips

# script usage
usage()
{
# if argument passed to function echo it
[ -z "${1}" ] || echo "! ${1}"
# display help
echo "\
# ffmpeg cross fade clips

$(basename "$0") -a clip1.(mp4|mkv|mov|m4v) -b clip2.(mp4|mkv|mov|m4v) -d (1|2) -o outfile.mp4
-a clip1.(mp4|mkv|mov|m4v) : first clip
-b clip2.(mp4|mkv|mov|m4v) : second clip
-d (1|2)                   : cross fade duration :optional agument # if option not provided defaults to 1 second
-o outfile.mp4             : optional agument # if option not provided defaults to infile-name-xfade-date-time"
exit 2
}

# error messages
NOTFILE_ERR='not a file'
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'

# if script is run arguments pass and check the options with getopts,
# else display script usage and exit
[ $# -gt 0 ] || usage "${WRONG_ARGS_ERR}"

# duration regex match 1
dur_long='^[1-2]\{1\}$'

# getopts check and validate options
while getopts ':a:b:d:o:h' opt
do
  case ${opt} in
     a) clip1="${OPTARG}"
	[ -f "${clip1}" ] || usage "${clip1} ${NOTFILE_ERR}";;
     b) clip2="${OPTARG}"
	[ -f "${clip2}" ] || usage "${clip2} ${NOTFILE_ERR}";;
     d) dur="${OPTARG}"
        expr "${dur}" : "${dur_long}" 1>/dev/null;;
     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))

# infile, infile name and extension
clip1_nopath="${clip1##*/}"
clip1_name="${clip1_nopath%.*}"

# file command check input file mime type
clip1_filetype="$(file --mime-type -b "${clip1}")"
clip2_filetype="$(file --mime-type -b "${clip2}")"

# audio and video mimetypes
mov_mime='video/quicktime'
mkv_mime='video/x-matroska'
mp4_mime='video/mp4'
m4v_mime='video/x-m4v'

# check the clips mime type
checkmime () {
case "${1}" in
    ${mov_mime}|${mkv_mime}|${mp4_mime}|${m4v_mime});;
    *) usage "${2} ${NOT_MEDIA_FILE_ERR}";;
esac
}

# check mime type
checkmime "${clip1_filetype}" "${clip1}"
checkmime "${clip2_filetype}" "${clip2}"

# clip durations for fades
clip1_dur=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$clip1" | cut -d\. -f1)
clip2_dur=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$clip2" | cut -d\. -f1)

# clip1 use the bc command to remove 1 second from length of clip for cross fade
clip1_offset=$(echo "${clip1_dur}-1" | bc -l)
clip2_offset=$(echo "${clip2_dur}-1" | bc -l)

# variables
outfile_default="${clip1_name}-xfade-$(date +"%Y-%m-%d-%H-%M-%S").mp4"
duration_default='1'

# cross fade video and audio
xfade_va () {
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${clip1}" -i "${clip2}" \
    -an -filter_complex \
    "   [0:v]trim=start=0:end='${clip1_offset}',setpts=PTS-STARTPTS[firstclip];
        [1:v]trim=start=${dur:=${duration_default}},setpts=PTS-STARTPTS[secondclip];
        [0:v]trim=start='${clip1_offset}':end='${clip1_dur}',setpts=PTS-STARTPTS[fadeoutsrc];
        [1:v]trim=start=0:end=${dur:=${duration_default}},setpts=PTS-STARTPTS[fadeinsrc];
        [fadeinsrc]format=pix_fmts=yuva420p,      
                    fade=t=in:st=0:d=${dur:=${duration_default}}:alpha=1[fadein];
        [fadeoutsrc]format=pix_fmts=yuva420p,
                    fade=t=out:st=0:d=${dur:=${duration_default}}:alpha=1[fadeout];
        [fadein]fifo[fadeinfifo];
        [fadeout]fifo[fadeoutfifo];
        [fadeoutfifo][fadeinfifo]overlay[crossfade];
        [firstclip][crossfade][secondclip]concat=n=3[output];
        [0:a] afade=t=in:st=0:d=${dur:=${duration_default}} [audiofadein];
        [1:a] afade=t=out:st='${clip2_offset}':d=${dur:=${duration_default}} [audiofadeout];
        [audiofadein][audiofadeout] acrossfade=d=${dur:=${duration_default}} [audio]
    " \
    -map "[output]" -map "[audio]" "${outfile:=${outfile_default}}"
}

# cross fade video
xfade_v () {
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${clip1}" -i "${clip2}" \
    -an -filter_complex \
    "   [0:v]trim=start=0:end='${clip1_offset}',setpts=PTS-STARTPTS[firstclip];
        [1:v]trim=start=${dur:=${duration_default}},setpts=PTS-STARTPTS[secondclip];
        [0:v]trim=start='${clip1_offset}':end='${clip1_dur}',setpts=PTS-STARTPTS[fadeoutsrc];
        [1:v]trim=start=0:end=${dur:=${duration_default}},setpts=PTS-STARTPTS[fadeinsrc];
        [fadeinsrc]format=pix_fmts=yuva420p,      
                    fade=t=in:st=0:d=${dur:=${duration_default}}:alpha=1[fadein];
        [fadeoutsrc]format=pix_fmts=yuva420p,
                    fade=t=out:st=0:d=${dur:=${duration_default}}:alpha=1[fadeout];
        [fadein]fifo[fadeinfifo];
        [fadeout]fifo[fadeoutfifo];
        [fadeoutfifo][fadeinfifo]overlay[crossfade];
        [firstclip][crossfade][secondclip]concat=n=3[output]
    " \
-map "[output]" "${outfile:=${outfile_default}}"
}

# check if video has an audio track
clip1_check="$(ffprobe -i "${clip1}" -show_streams -select_streams a -loglevel error)"
clip2_check="$(ffprobe -i "${clip2}" -show_streams -select_streams a -loglevel error)"

# check if audio_check is null which means the video doesnt have an audio track
if [ -z "${clip1_check}" ] || [ -z "${clip2_check}" ]; then
   xfade_v "${clip1}" "${clip2}" # fade video track
else
   xfade_va "${clip1}" "${clip2}" # fade video and audio track
fi