idetect

#!/usr/bin/env bash

# idetect.sh
# attempts to detect if video is interlaced
# "should be" non-destructive

AUTHOR="Chris Reid"
EMAIL="spikeysnack@gmail.com"
DATE="13 FEB 2017"

FF=$(which ffmpeg)

# you can try more or less frames, accuracy improves with more, but takes longer
frames=256

# throwing away video so just go raw
format="rawvideo"

# example output
#[Parsed_idet_0 @ 0x38e3000] Single frame detection: TFF:0 BFF:368 Progressive:101 Undetermined:44
#[Parsed_idet_0 @ 0x38e3000] Multi frame detection: TFF:0 BFF:481 Progressive:10 Undetermined:22

# filter the relevant part
OUT=$("${FF}" -filter:v idet -frames:v "${frames}" -an -f "${format}" -y /dev/null  \
    -i "${1}" 2>&1 | grep 'Parsed_idet' )

# parse into array
testString="${OUT}"
array=( $testString )

# iterate the array
alen=${#array[@]} # num items in array
for n in $(seq 0 $alen) #
do
    # Top Field First (TFF)  or Bottom Field First (BFF)
    if [ "${array[$n]:0:3}" == "TFF" ]  ||  [ "${array[$n]:0:3}" == "BFF" ]; then
        echo "${array[$n]}"
        S="${array[$n]}"
        N="${S#*:}"
#   echo "N" "${N}"
    fi

    if [ "${array[$n]:0:11}" == "Progressive" ] ; then
        echo "${array[$n]}"
        S="${array[$n]}"
        P="${S#*:}"
    fi
done

# colors
normal="$(tput sgr0)"
black="$(tput setaf 0)"
red="$(tput setaf 1)"
green="$(tput setaf 2)"

# decisions
if [ $((N)) -gt 0 ]  &&  [ $((P)) -lt $((N)) ] ; then
    echo -e "${green}YES probably interlaced${normal}"
else
    echo -e "${red}NO probably not interlaced ${normal}"
fi