Burn-in reverse timecode (countdown)

[IxTab]

Is there a method to batch burn-in reverse timecode (countdown) in .mp4 video files? I am using VSDC Video Editor but I have to manually work on every single file and unfortunately i would have to apply it on dozens of videos.
I have tried to use FFMPEG or Avisynth but have not found anything that works to produce the countdown of the total duration of the video.

The only code I've tried with FFMPEG is this:

1 input=input.mp4
2 duration=$(ffprobe -loglevel error -show_entries format=duration -of default=nw=1:nk=1 "$input")
3 ffmpeg -i "$input" -vf "drawtext=fontfile=OpenSans-Regular.ttf:text='%{eif\:$duration-t\:d}':fontcolor=white:fontsize=24:x=w-tw-20:y=th:box=1:boxcolor=black@0.5:boxborderw=10,format=yuv420p" -c:v libx264 -c:a copy -movflags +faststart output.mp4

but i can't use it as i don't mean programming or coding.
My o.s. is win 8.1 x64.

Can anyone suggest me a solution?

[poisondeathray]

For avisynth you could use Reverse().ShowTime().Reverse() . There are various batch scripters for avisynth and various options for positioning, fonts, colors etc..
http://avisynth.nl/index.php/ShowFrameNumber#ShowTime



For ffmpeg, reversing can be tricky with timestamps and memory issues, you can try a similar approach but I doubt it will work

https://www.ffmpeg.org/ffmpeg-filters.html#reverse

Reverse a video clip.

Warning: This filter requires memory to buffer the entire clip, so trimming is suggested.

[IxTab]

As you suggested I found a great solution for my question using Avisynth together with this script and this timer.
Thank you.