transcode-ntsc

#!/bin/bash
set -eu

if [ $# -eq 0 ]; then cat << EOF

Transcodes an interlaced NTSC video to MKV (x264)

${0} [options] input.mpg [output.mkv]

    Options:

    -s [HH:[MM:]]SS     Starts transcoding from this timecode.

    -t [HH:[MM:]]SS     Ends transcoding at this timecode.

    -x CODEC            Uses a hardware-accelerated video codec.
                        Hardware encoding trades space for extreme speed.
                        Set "ffmpeg=/path/to/ffmpeg" to use a custom build.

                        Known hardware codecs:
                            h264_nvenc

If no output file name is given, it defaults to a similarly named
MKV in the working directory.

Output file size per hour of transcoded video:

    x264 (default)  ~1GB/hr
    h264_nvenc      ~1.5GB/hr

EOF
    exit 1
fi

ffmpeg=${ffmpeg:-ffmpeg}

StartTime=""
EndTime=""
VideoCodec="libx264"
VideoOpts="-crf 23 -preset veryslow"
while getopts ":s:t:x:" opt; do case $opt in
    s) StartTime="-ss ${OPTARG}"
    ;;
    t) EndTime="-t ${OPTARG}"
    ;;
    x) VideoCodec="${OPTARG}"
        case $VideoCodec in
            h264_nvenc)
                # x264 has better bang per bit. try to match x264 crf 23.
                # this is ~1.5GB/hr (but it's so fast uwu)
                #          avg        avgq   vbr        same as x264     slowest(implied 2pass+cabac)
                VideoOpts="-b:v 3000k -cq 19 -rc vbr_hq -rc-lookahead 60 -preset slow -profile:v high"
            ;;
        esac
    ;;
esac done
shift $((OPTIND-1))

Input="${1}"
if [ $# -eq 1 ]; then
    Basename=$(basename "${Input}")
    Output="${Basename%.*}.mkv"
else
    Output="${2}"
fi

$ffmpeg \
    $EndTime \
    -hwaccel auto \
    -i "${Input}" \
    -c:a copy \
    -vf "yadif" \
    -c:v ${VideoCodec} \
    ${VideoOpts} \
    -metadata creation_time="$(date --iso-8601=seconds)" \
    -movflags +faststart \
    $StartTime \
    "${Output}"