Scale or pad second stream to the first one

@echo off
setlocal EnableDelayedExpansion

set "img1=%~1"
set "img2=%~2"
set "outfile=%~dp1%~n1_tit.jpg"

for /f "tokens=5 delims==_" %%i in ('ffprobe -v error -of flat^=s^=_ -select_streams v:0 -show_entries stream^=height "%img1%"') do set "HEIGHT=%%i"
echo %HEIGHT%

rem This will SCALE second image to the height of the first one
rem ffmpeg -i "%img1%" -i "%img2%" -filter_complex "[1][0]scale=-1:h=ref_h[img2s]; [0][img2s]hstack=inputs=2[out]" -map [out] "%outfile%"

rem This will PAD second image to the height of the first one
ffmpeg -i "%img1%" -i "%img2%" -filter_complex "[1]pad=w=iw+1:h=%HEIGHT%:x=0:y=0:color=black[img_pad]; [0][img_pad]hstack=inputs=2[out]" -map [out] "%outfile%"
pause