Stack 3 videos with Padding if necessary

[Budman1]

After searching and trying many examples in both Avisynth and ffmpeg, none of the methods I have tried will stack 3 videos with padding for a final result of 854x480.. for example I have 3 videos with widths of 252, 100, 252 respectively with the height all the same 360 and I would like to stack horizontally with (I assume) padding left and right after the height is adjusted to 480(480/360=1.333333AR , 252*1.333333=336 width video1, 1.333333*100=134 width video2, 252*1.333333=336 width video3.

I'm assuming that would leave all 3 stacked for a total width of 336+134+336=806. This would need padding pillar bars of 24 at each side. I don't mind if its avisynth stack or ffmpeg hstack but I cannot get any scripts to work.

Any help would be greatly appreciated.
Thank You

[LigH.de]

Should be rather simple in AviSynth... replace YourFavSource and YourFavResize with appropriate filters and provide the file names as strings.

left = YourFavSource(leftfilename).YourFavResize(336,480)
center = YourFavSource(centerfilename).YourFavResize(134,480)
right = YourFavSource(rightfilename).YourFavResize(336,480)
StackHorizontal(left,center,right)
AddBorders(24,0,24,0)

If something fails, report the exact error messages. There are a few constraints, e.g. color spaces must match...

[Budman1]

Thank you LigH.de . Works like a charm. Never thought of using add borders but that is better since I can compute/alter those odd (not divisible by 2 for YUV) borders and video size as well.
Thank you again.