This script converts dashcam videos into geotagged still images

vid2pix.sh

#! /bin/bash

# This script converts dashcam videos into geotagged still images 
# - extraction with ffmpeg of key images
# - extraction of GPS location and time using OCR
# - sub-second metadata generation
# - image cropping and optimization
#
# Tested with ThiEYE carview4 dashcam (front and back)

if [ $# = 0 ]
then
  echo "Usage: vid2pix.sh VIDEO_PATH [COMMON_EXIF_TAGS]"
  echo "  170° front camera: vid2pix.sh myvideo.MP4 \"-make=ThiEYE -mode=Carview4 -FocalLength=1 -FocalLengthIn35mmFormat=2 -FocusDistance=0\""
  echo "  140° back camera:  vid2pix.sh myvideo.MP4 \"-make=ThiEYE -mode=Carview4 -FocalLength=2 -FocalLengthIn35mmFormat=6 -FocusDistance=0\""
  exit
fi

VIDEO=$1
EXIF=$2

DIR=$(dirname $VIDEO)_$(basename "$VIDEO" .MP4)

mkdir -p $DIR

if [ ! -e "$DIR/frame-0001.jpg" ]
then
    ffmpeg -loglevel 0 -skip_frame nokey -i $VIDEO -f image2 -threads 1 -vsync 0 -qscale:v 2  $DIR/frame-%04d.jpg
fi

for FRAME in $(ls -1 $DIR/frame-*.jpg)
do
    # generate 1:8 preview
    convert $FRAME -resize 6.25% -strip $DIR/temp.jpg
    # generate cropped time/GPS extract from picture
    convert $FRAME -gravity SouthWest -crop 270x90+0+0 -brightness-contrast 0x80 -colorspace gray -negate $DIR/temp.png
    # OCR it !
    tesseract --dpi 72 --psm 6 --user-patterns patterns.txt $DIR/temp.png $DIR/temp conf

    TIMESTAMP=20$(egrep -o '[0-9]{2}/[0-9][0-9]/[0-9][0-9] [0-9][0-9]:[0-9][0-9]:[0-9][0-9]' $DIR/temp.txt)

    # could not find DATE and TIME ?
    if [ "$TIMESTAMP" = "20" ]
    then
        # extract TIME
        TIME=$(egrep -o '[0-9][0-9]:[0-9][0-9]:[0-9][0-9]' $DIR/temp.txt)
        # use previous DATE
        TIMESTAMP=$(echo $PREV_TIME | sed 's/ .*/ /')$TIME
    fi

    LAT=$(egrep -o '([NS]) ?[0-9]+[\.,]?[0-9]{5}' $DIR/temp.txt | sed 's/,/./;s/ //g;s/S/-/;s/N//;s/\([0-9]\)\([0-9]\{5\}\)$/\1.\2/')
    LON=$(egrep -o '([EFW]) ?[0-9]+[\.,]?[0-9]{5}' $DIR/temp.txt | sed 's/,/./;s/ //g;s/W/-/;s/E//;s/F//;s/\([0-9]\)\([0-9]\{5\}\)$/\1.\2/')

    echo "$FRAME - $TIMESTAMP - $LAT - $LON"
    cat $DIR/temp.txt

    # subsec
    if [ "$TIMESTAMP" = "$PREV_TIME" ]
    then
        SUBSEC="500"
    else
        SUBSEC="000"
        LAT=$LAT"0"
        LON=$LON"0"
        LAT2=$(echo "scale=6;($LAT+$PREV_LAT)/2" | bc)
        LON2=$(echo "scale=6;($LON+$PREV_LON)/2" | bc)
        if [ "$LAT $LON" = "$LAT2 $LON2" ]
        then
            # no move ? delete
            rm $PREV
        else
            # adjust interpolated location
            exiftool -q -overwrite_original -GPSLatitude="$LAT2" -GPSLongitude="$LON2" $PREV
            touch -d "$PREV_TIME" $PREV
        fi
    fi

    exiftool -q -overwrite_original -DateTimeOriginal="$TIMESTAMP" -SubSecTimeOriginal="$SUBSEC" -GPSLatitude="$LAT" -GPSLongitude="$LON" "-thumbnailimage<=$DIR/temp.jpg" $EXIF $FRAME

    # crop, optimize & rename JPEG file
    WIDTH_HEIGHT=$(file $FRAME| egrep -o '[0-9]+x[0-9]+')
    WIDTH=$(echo "$WIDTH_HEIGHT" | sed 's/x.*//')
    HEIGHT=$(echo "$WIDTH_HEIGHT" | sed 's/.*x//')
    CROP="$WIDTH"x$(echo "$HEIGHT-120" |bc)

    OUTPUT=$(dirname $FRAME)/$(echo "$TIMESTAMP.$SUBSEC" | sed 's! !T!g;s!/!-!g').jpg

    jpegtran -optimize -progressive -copy all -crop $CROP $FRAME > "$OUTPUT"
    # adjust file modification date-time to capture time
    touch -d "$TIMESTAMP" $OUTPUT

    # echo "$OUTPUT > $LAT / $LON @ $TIMESTAMP.$SUBSEC"

    PREV=$OUTPUT
    PREV_LAT=$LAT
    PREV_LON=$LON
    PREV_TIME=$TIMESTAMP

done
rm $DIR/temp* $DIR/frame*