Creates 3x3 thumbnails preview

#grid_thumbs.cmd

(
    for %%f in (
        *.mp4 *.mkv *.mov *.3gp
    ) do (
        for /f %%g in (
            'ffprobe -v error -select_streams v:0 -count_packets -show_entries stream^=nb_read_packets -of default^=nk^=1:nw^=1 "%%f"'
        ) do (
                ffmpeg -y -i "%%f" -filter_complex "select='not(mod(n,floor(%%g/9)))',tile=layout=3x3" -update 1 -frames:v 1 "%%f.png"
        )
    )
)