FFMPEG Movie Encode Script

movenc.sh

#!/usr/bin/env bash

# Usage:
#   movenc.sh <infile> [<outfile>]
#
# User variables/args:
#   CROP - ffmpeg crop filter of format xx:xx:xx:xx
#   ASTREAMS - ffmpeg audio stream
#   SSTREAMS - ffmpeg subtitle stream
#   TUNE - x264 tune
#
# Dependencies:
# ffmpeg with libfdk_aac and x264
# jq

for arg in "${@}"; do
    case "${arg}" in
        --astreams=*)
            ASTREAMS="${arg#*=}"
            shift
            ;;
        --sstreams=*)
            SSTREAMS="${arg#*=}"
            shift
            ;;
        --crop=*)
            CROP="${arg#*=}"
            shift
            ;;
        --tune=*)
            TUNE="${arg#*=}"
            shift
            ;;
    esac
done

# needs 1 arg, a file that exists
[[ ! -f "${1}" ]] && echo "File \"${1}\" doesn't exist." && exit 1

# arg $1 is input file
infile="${1}"

# arg $2 is output file (defaults to ${infile%.*}+done.mkv)
outfile="${2:-${infile%.*}+done.mkv}"

# get ffprobe attribute for v:0
get_vattr() {
    ffprobe -i "${infile}" -v quiet -print_format json \
        -show_streams -select_streams v:0 \
        | jq --raw-output ".streams[0].${1}"
}

# get sample_aspect_ratio via ffprobe
get_sar() {
    get_vattr 'sample_aspect_ratio' | sed -e 's|:|/|'
}

# get resolution via ffprobe if not cropped, else use crop resolution
get_width() {
    if [[ -z "${CROP}" ]]; then
        echo -n "$(get_vattr 'width')"
    else
        echo -n "${CROP}" | awk -F ':' '{ print $1 }'
    fi
}
get_height() {
    if [[ -z "${CROP}" ]]; then
        echo -n "$(get_vattr 'height')"
    else
        echo -n "${CROP}" | awk -F ':' '{ print $2 }'
    fi
}

# get crop filter string
get_crop() {
    [[ -n "${CROP}" ]] && echo -n ",crop=${CROP}"
}

# $1: stream_spec $2: tag
get_tag_for() {
    ffprobe -i "${infile}" -v quiet -print_format json \
        -show_streams -select_streams "${1#0:}" \
        | jq --raw-output ".streams[0].tags.${2}"
}

add_vflags() {
    local fps gop
    fps="$(get_vattr 'r_frame_rate' | bc)"
    _FFMPEG_ARGS+=( -c:v libx264 )
    # set preset based on res (576 is PAL DVD)
    if (( $(get_height) > 576 )); then
        _FFMPEG_ARGS+=( -preset slower )
    else
        _FFMPEG_ARGS+=( -preset veryslow )
    fi
    # considered "visually lossless"
    _FFMPEG_ARGS+=( -crf 17 )
    # optionally add a tune
    if [[ -n "${TUNE}" ]]; then
        _FFMPEG_ARGS+=( -tune "${TUNE}" )
    fi
    # GOP is 10*fps capped at 300
    gop="$(( "${fps}" * 10 ))"
    if (( ${gop} >= 300 )); then
        _FFMPEG_ARGS+=( -g 300 )
    else
        _FFMPEG_ARGS+=( -g "${gop}" )
    fi
    # always apply sar filter to get correct aspect ratio
    # conditionally add crop filter
    _FFMPEG_ARGS+=( -vf "setsar=$(get_sar)$(get_crop)" )
}

# unconditional libfdk_aac with -vbr 5
add_aflags() {
    _FFMPEG_ARGS+=(
        -c:a libfdk_aac
        -vbr 5
    )
}

# for now nothing fancy, just copy
add_sflags() {
    _FFMPEG_ARGS+=(
        -c:s copy
    )
}

# map streams and some metadata
add_mappings() {
    local i val
    # map global metadata
    _FFMPEG_ARGS+=( -map_metadata 0 )

    # map video
    _FFMPEG_ARGS+=( -map 0:v:0 )

    # no default metadata mappings
    _FFMPEG_ARGS+=( -map_metadata:s:v -1 )
    _FFMPEG_ARGS+=( -map_metadata:s:a -1 )
    _FFMPEG_ARGS+=( -map_metadata:s:s -1 )

    # map audio and subtitles only keeping language and title metadata
    # audio
    i=0
    for s in ${ASTREAMS}; do
        _FFMPEG_ARGS+=( -map "${s}" )
        # make first track the default
        _FFMPEG_ARGS+=( "-disposition:a:${i}" "$([[ "${i}" -eq 0 ]] && echo -n default || echo -n 0)" )
        for tag in language title; do
            val="$(get_tag_for "${s}" "${tag}")"
            [[ "${val}" != "null" ]] && _FFMPEG_ARGS+=( "-metadata:s:a:${i}" "${tag}=${val}" )
        done
        i=$(( ${i} + 1 ))
    done

    # subtitles
    i=0
    for s in ${SSTREAMS}; do
        _FFMPEG_ARGS+=( -map "${s}" )
        for tag in language title; do
            val="$(get_tag_for "${s}" "${tag}")"
            [[ "${val}" != "null" ]] && _FFMPEG_ARGS+=( "-metadata:s:s:${i}" "${tag}=${val}" )
        done
        i=$(( ${i} + 1 ))
    done
}

# build ffmpeg args
declare -a _FFMPEG_ARGS
add_vflags
add_aflags
add_sflags
add_mappings

# form ffmpeg command for encode, PRETEND only echos command
$([[ -n "${PRETEND}" ]] && echo echo) \
ffmpeg -i "${infile}" "${_FFMPEG_ARGS[@]}" "${outfile}"