Here is a Nautilus Script

- Select files in nautilus

- Right-click on it

- In context menu, select Script > NameOfScript

Installation:

Install the mediainfo program if not present sudo apt install mediainfo

Save the script to a file in ~/.local/share/nautilus/scripts

Make it executable chmod +x ~/.local/share/nautilus/scripts/scriptname

Visit the scripts directory once with nautilus nautilus ~/.local/share/nautilus/scripts

#!/bin/bash



# Selected fileslist to Array

OLDIFS=$IFS

IFS=$'

'

fileArray=($NAUTILUS_SCRIPT_SELECTED_FILE_PATHS)

IFS=$OLDIFS



# Length of array: total num of selected files

NbFiles=${#fileArray[@]}



# The loop 

for (( i=0; i < ${NbFiles}; i++ ));

do

    # Get duration if file is media (audio or video)

    buff=$(file -N -i "${fileArray[$i]}" | grep -E 'audio|video')

    if [ ! -z  "$buff" ]

        then

            # mediainfo gives duration in milliseconds, easy to sum up

            MediaDuration=$(mediainfo --Output='General;%Duration%' "${fileArray[$i]}")

            TotalDuration=$((TotalDuration + MediaDuration))

            NbMedia=$((NbMedia + 1))

    fi

done



# Format Duration: milliseconds to H:M:S

Seconds=$((TotalDuration / 1000))

FormattedDuration=$(printf '%02dh:%02dm:%02ds

' $(($Seconds/3600)) $(($Seconds%3600/60)) $(($Seconds%60)))



# Build report

ReportText="${NbFiles} File"

test $NbFiles -gt 1 && ReportText="${ReportText}s"

ReportText="${ReportText} selected

"

test $NbMedia -gt 0 && ReportText="${ReportText}${NbMedia} media file" || ReportText="${ReportText}No media file"

test $NbMedia -gt 1 && ReportText="${ReportText}s"

test $NbMedia -gt 0 && ReportText="${ReportText}

Total duration: ${FormattedDuration}"



zenity  --info --no-wrap --text="${ReportText}"