RecodeMOVsToSmaller.sh

#!/bin/bash
function show_help {
    echo "Usage: $0 [-g SSSS [ActionVerb=FOO, GO required to start processing] ] [-v verbose] [-h help] [-a NN [maxAgeMonths=6]] [-b noBackup = False][-c NN maxCRF=30 ] [-e SSS EXT=mov;mpg ] [-d SSSSS backup staging dir [default=based on EXT] ] [-p purge old files [False] ] [-s NN max number of Dim scaling events [5] ]" >&2
    exit 1
}

####################################
#reset date values of file after clearing exif tags:
# touch /tmp/foo.txt;find . -type f -iname "*.mov" -print0 | while IFS= read -r -d '' file;do touch -r $file /tmp/foo.txt;exiftool -xmp:credit= "$file";touch -r /tmp/foo.txt "$file";done
####################################

###################################
# Copy files from backup back to original folder
# basedir=~/Movies/20180304204328_SHRINKY; find . -type f -iname "*.mov" -print0 | while IFS= read -r -d '' file;do basen=`basename ${file}`;cp $basedir/$basen $file;done
##################################

# A POSIX variable
OPTIND=1         # Reset in case getopts has been used previously in the shell.

# Initialize our own variables:
output_dest=XXXXX
verbose=0
EXT="mov;mpg" 
maxAgeMonths=16
maxCRF=30
noBackup=0
noPurge=1
maxDimenScalings=5

#require a "GO" to start processing for safety
ActionVerb=FOO           

while getopts "g:h?va:bc:d:e:s:" opt; do
    case "$opt" in
	a)  maxAgeMonths=$OPTARG
	    ;;
	c)  maxCRF=$OPTARG
	    ;;
	b)  noBackup=1
	    ;;
	d)  output_dest=$OPTARG
            ;;
	e)  EXT=$OPTARG
	    ;;
	g)  ActionVerb=$OPTARG
	    ;;
	h|\?)
            show_help
            exit 0
            ;;
	p)  noPurge=0
	    ;;
	s)  maxDimenScalings=$OPTARG
	    ;;
	v)  verbose=1
            ;;
    esac
done

shift $((OPTIND-1))

[ "$1" = "--" ] && shift

sessionID=`date +%Y%m%d%H%M%S`
tmpfile=/tmp/${RANDOM}_placeholder.txt

while IFS=';' read -ra ADDR; do
  for THISEXT in "${ADDR[@]}"; do
      # process "$i"
      printf "|==================================================|\n Processing Extension:%s\n|==================================================|\n " $THISEXT
#	echo Processing Extension $THISEXT
	dest=/tmp/${RANDOM}_output.${THISEXT}

	if [ $output_dest == 'XXXXX' ]; then
	    case "$THISEXT" in
		m[op][gv4]   )
		    backupStagingDir=~/Movies/${sessionID}_SHRINKY
		    ;;
		[jp][pn]g   )
		    backupStagingDir=~/Pictures/${sessionID}_SHRINKY
		    ;;
		*)
		    backupStagingDir=/tmp/${sessionID}_SHRINKY
		    ;;
	    esac
	else
	    backupStagingDir=$output_dest
	fi


	if [ ! -d $backupStagingDir ]; then
	    echo destination directory for originals $backupStagingDir not found
	    echo creating $backupStagingDir
	    mkdir $backupStagingDir
	    if [ ! -d $backupStagingDir ]; then
			echo creating dest for originals dir failed!!!
			exit 1
	    fi
	fi

	logfile=$backupStagingDir/ZZZZ_AgingHistory.log
	touch $logfile
	recoveryfile=$backupStagingDir/ZZZZ_${sessionID}_RecoveryFile.log


	cnt=0
	echo EXECUTING: maxCRF ${maxCRF}   maxAgeMonths ${maxAgeMonths}  ActionVerb ${ActionVerb}
	echo EXECUTING: find . -type f -iname \"*.${THISEXT}\" -print0
	find . -type f -iname "*.${THISEXT}" -print0 | while IFS= read -r -d '' file
	do  
	    #print0eserve the access times of the file in a temp file
	    rm $tmpfile
	    touch -r "$file" $tmpfile
	    filebasename=`basename $file`
	    #calculate file age in months
	    age=$((($(date +%s) - $(stat -t %s -f %m -- "$file")) / 86400 / 30))
	    fileDTG=$(stat -f "%Sc" -t "%Y%m%d%H%M" "$file")
	    ager=$(stat -f "%Sm" -t "%Y%m%d%H%M" "$file")
	    printf "Oo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oO\n FileName:%s\n Age in Months:%2d Creation Date:%s Last Access:%s" "$file" $age $fileDTG $ager 
	    if [ "$age" -gt "$maxAgeMonths" ]; then 
			printf " OLD FILE... %s   %s  " $age $maxAgeMonths
			if [ $ActionVerb == 'GO' ]; then
			    if [ $noPurge == 0 ]; then 
					rm "$file"
					printf " Purging...file deleted!\n"
			    else
					printf " NO-ACTION: Purge of old files not enabled \n"
			    fi
			else
		    	printf " NO-ACTION: rm %s\n" $file
			fi
	    else 
			printf " Aging File.. \n"
			mycrf=$(dc -e "[$(($age + 23))]sM ${maxCRF}d $(($age + 23))<Mp")
			#checking the exif tags to see if we've handled this file before
			CHECKIN=$(exiftool -xmp:credit "$file") 
			arrCHECKIN=(${CHECKIN//:/ })
			if [[ ${arrCHECKIN[1]} == "XXXXAGED_FILE" ]]; then 
			    printf ' Previously Aged File! Prior CRF is:%s  Last time aged:%s \n' ${arrCHECKIN[3]} ${arrCHECKIN[4]}
		    	printf ' Number of times aged:%s  Dimension Scaler:%s \n' ${arrCHECKIN[5]} ${arrCHECKIN[2]}
			    if [ "${arrCHECKIN[4]}" -ge "$age"  ]; then
					#TODO skip or process file
					printf " File age (%s) is same or less than age at last script run (%s).  Skipping this file.\n" ${arrCHECKIN[4]} $age
					continue
			    fi
			else 
			    printf " First Time handling this file..."
			    printf "   Tagging File..."
			    #Tag Format: XXXXAGED_FILE:
			    #     ... [dimension scaller-float 0-1]:
			    #     ... [CRF at last resize- byte 1-31]:
			    #     ... [age @ last time shrunk - integer]
			    #     ... [number of times aged  - integer]
			    arrCHECKIN=(Credit XXXXAGED_FILE 0.75 $mycrf $age 0)
			    if [ $ActionVerb == 'GO' ]; then
			    	exiftool -xmp:credit=XXXXAGED_FILE:0.75:$mycrf:$age:0 "$file"
				    #transcribe the access times back to the original file
				    touch -r $tmpfile "$file"
				else
					exiftoolCMD="exiftool -xmp:credit=XXXXAGED_FILE:0.75:$mycrf:$age:0 '$file'"
		 			echo NO ACTION! skipped.. $exiftoolCMD
		 			printf " NO-ACTION: touch -r %s %s\n"  $tmpfile "$file"
				fi
			    if [ "$noBackup" -gt "0" ]; then
					printf " Skipping backup...\n"
			    else
					printf " Creating a backup of the file in the Staging Area (for offload to Google Drive or Dropbox)..."
					if [ $ActionVerb == 'GO' ]; then
					    cp "$file" "$backupStagingDir/."
					    touch -r "$file" "$backupStagingDir/$basename"
					    printf "done!\n"
					else
			 		   printf "NO ACTION! skipped..\n"
					fi
		    	fi
		    fi
		    echo arrCHECKIN[5] = ${arrCHECKIN[5]}    maxDimenScalings = "$maxDimenScalings"
		    if [ "${arrCHECKIN[5]}" -lt "$maxDimenScalings" ]; then 
				#stop scaling dimension down
				dimScalerTerm=""
				printf "No Dimension Scaling - exceeded max number. "
		    else
				#continue scaling down dimension
				dimScalerTerm="-vf scale=iw*${arrCHECKIN[3]}:ih*${arrCHECKIN[3]}"
				printf "Dimension Scaler Term: %s " $dimScalerTerm
		    fi
		    if [ $ActionVerb == 'GO' ]; then
				echo " AGING the file. CRF: ${mycrf}"
				echo EXECUTING: ffmpeg -y -i "$file" -nostdin -vcodec libx264 -profile:v main -level 3.1 -preset medium -crf $mycrf $dimScalerTerm -x264-params ref=4 -acodec libmp3lame -q:a 9 -movflags +faststart "$dest"
				ffmpeg -y -i "$file" -nostdin -vcodec libx264 -profile:v main -level 3.1 -preset medium -crf $mycrf $dimScalerTerm -x264-params ref=4 -acodec libmp3lame -q:a 9 -movflags +faststart "$dest"
			    #transcribe original file creation date onto new file
				touch -t $ager "$dest"
			    #transcribe file's exif tags and mark the file as having been aged
				exiftool -tagsFromFile "$file" "$dest"
				exiftool -xmp:credit=XXXXAGED_FILE:$mycrf:$age:$( ${arrCHECKIN[5]} + 1 ) "$dest"
				echo " SOURCE FILE:" `ls -larth "${file}"` " REDUCED FILE:" `ls -larth "${dest}"`
				mv "${dest}" "${file}"
		    else
				printf " NO-ACTION: ffmpeg -y -i \"%s\" -vcodec libx264 -profile:v main -level 3.1 -preset medium -crf %s %s -x264-params ref=4 -acodec libmp3lame -q:a 9 -movflags +faststart %s\n" "$file" $mycrf $dimScalerTerm $dest
				printf " NO-ACTION: touch -r %s %s\n"  $ager $dest
		    fi
	    fi
	#    if [[ $cnt > 6 ]]; then 
	#	echo "EXITING..."
	#	exit 1
	#    fi
	    cnt=$(($cnt+1))
	done
    printf "\nDoing Cleanup for Extension:%s\n|==================================================|\n " $THISEXT
	if [ -f ${dest} ] ; then
	    rm ${dest}
	fi
	if [ -f ${tmpfile} ] ; then
	    rm $tmpfile
	fi
  done
done <<< "$EXT"
echo "EXITING...."

Need to look at: https://stackoverflow.com/questions/192249/how-do-i-parse-command-line-arguments-in-bash to improve input.