#!/usr/bin/env mksh
# Make a video clip from a larger video

usage() {
    if [ -n "$1" ] ; then
        echo "$1" >&2
    fi
    echo "usage: $0 to-clip start-time end-time clipname" >&2
    echo "example:" >&2
    echo "  $0 ToClip.mkv 00:15:00.0 00:15:30.0 sickflips" >&2
    exit 1
}

die() {
    echo "err: $1" >&2
    exit 1
}

origfile=$1
starttime=$2
endtime=$3
clipname=$4

if [ -z "$origfile" ] || [ -z "$starttime" ] || [ -z "$endtime" ] || [ -z "$clipname" ]
then
    usage
fi

if ! [ -f "$origfile" ] ; then
    usage "$origfile doesn't exist!"
fi

duration=$(( $(gdate -d "$endtime" "+%s") - $(gdate -d "$starttime" "+%s") )) || usage "Couldn't get clip duration"

[ "$duration" -gt 0 ] || usage "end-time should be after start-time"

strduration="$(gdate -ud "@${duration}" "+%H:%M:%S.%N" | cut -c-10)"

if [ -n "$SUBSFILE" ] ; then
    ffmpeg -ss "$starttime" -copyts -i "$origfile" -ss "$starttime" -t "$strduration" -c:v libx264 -c:a mp3 -ac 2 -vf subtitles="$SUBSFILE" "$clipname.mp4"
else
    ffmpeg -ss "$starttime" -i "$origfile" -t "$strduration" \
            -c:v libx264 -c:a mp3 $FFMPEG_PARAM -ac 2 \
            "$clipname.mp4"
fi