AVI synth montage script

gistfile1.txt

This is the avisynth script ("montage.avs"):
---
Setmemorymax(512)
SetMTMode(2,4)
grid=24
a1=directshowsource("input1.webm",audio=false).converttorgb
l=ceil(float(a1.framecount)/(grid*grid))


function HRepeat(clip c, int g, int l, int x, int y) {
x == g-1 ? c.trim(l*(g-1+g*y),-l) : StackHorizontal(c.trim(l*(x+g*y),-l), HRepeat(c, g, l, x+1, y))
}

function VHRepeat(clip c, int g, int l, int x, int y) {
HR = StackHorizontal((x==0 && y==0)? blankclip(c.trim(0,-l)):c.trim(l*(g-1+g*(y-1)),-l), HRepeat(c, g, l, x, y))
y == g-1 ? HR : StackVertical(HR, VHRepeat(c, g, l, x, y+1))
}

VHRepeat(a1,grid,l,0,0)
animate(0, l, "crop", a1.width, 0, a1.width*grid, a1.height*grid, 0, 0, a1.width*grid, a1.height*grid)
converttoyv12
---

To do a static version just replace the HR = StackHorizontal(...) line with:
HR = HRepeat(c, g, l, x, y)
and also delete the animate line.

And this is the batch script:
---
@echo off
ffmpeg -v verbose -i "%~1" -threads 4 -c:v libvpx -crf 4 -b:v 3000K -vf scale=80:36 -an input1.webm
ffmpeg -v verbose -i "montage.avs" -threads 4 -c:v libvpx -crf 4 -b:v 2360K -vf scale=1280:576 -an output1.webm -y
---

I found re-encoding first to a small size worked better than just resizing in the script, but YMMV. You might need to adjust the scaling if the resized video would have odd-numbered height (as I've done there - using scale=80:-1 would result in a height of 35 and crash avisynth). Normally I just use scale=160:-1 (and 640:-1 for the final size) for making the smaller (12x12) grids.

Bit-rate calculation is (3*8*1024^2*grid^2/(length of original in seconds))* (fudge factor ~0.975)

Once you've edited the bat file, just drag and drop the target video onto it to start.