this script will help you to get duration of video in the directory

Get-VideoDetails.ps1

Function Get-VideoDetails {
    param ($targetDirectory)
    $LengthColumn = 27
    $objShell = New-Object -ComObject Shell.Application
    $total_duration = [timespan] '00:00:00'
    
    Get-ChildItem -LiteralPath $targetDirectory -Include *.mp4 -Recurse -Force | ForEach {
        if ($_.Extension -eq ".mp4"){
            $objFolder = $objShell.Namespace($_.DirectoryName)
            $objFile = $objFolder.ParseName($_.Name)
            $Duration = $objFolder.GetDetailsOf($objFile, $LengthColumn)
            $time_span = [timespan]$Duration
            $total_duration += $time_span

            New-Object PSObject -Property @{
                Name = $_.Name
                Duration = $time_span
            }
        }
    }
    Write-Output $total_duration.ToString()
}