Selectable BatchFile for ffmpeg(any)

selectableffmpeg.bat

rem preparation command
set pwshcmd=powershell -noprofile -command "&{[System.Reflection.Assembly]::LoadWithPartialName('System.windows.forms') | Out-Null;$OpenFileDialog = New-Object System.Windows.Forms.OpenFileDialog; $OpenFileDialog.ShowDialog()|out-null; $OpenFileDialog.FileName}"

rem exec commands powershell and get result in FileName variable
for /f "delims=" %%I in ('%pwshcmd%') do set "FileName=%%I"

@echo off
setlocal

set "psCommand="(new-object -COM 'Shell.Application')^
.BrowseForFolder(0,'Please choose a folder.',0,0).self.path""

for /f "usebackq delims=" %%I in (`powershell %psCommand%`) do set "folder=%%I"

setlocal enabledelayedexpansion
echo You chose !folder!

c:\ffmpeg-3.4.2-win64-static\bin\ffmpeg.exe -i %FileName% -vcodec png -r 10 !folder!\image_%%04d.png

endlocal

pause