Ha! Ofcourse! Don't know why I didnt think of that.
I will be posting a dance with your past self patch soon with this knowledge! This was the last technical hurdle.

Working on a patch which takes the output of pix_write, and tries to read it in pix_multiimage.

The problem is that pix_write creates a sequence of images with many trailing zeros like so:

filename00000.jpg
filename00001.jpg
filename00002.jpg
etc...

While pix_multiimage expects a folder of images like so:

filename0.jpg
filename1.jpg
filename2.jpg
etc...

I see nothing in the documentation to either remove the trailing zeros in pix_write, or add trailing zeros to pix_multiimage. The second I rename each file by hand, it works. But I want my patch to pass between these two objects on the fly.

It is quite annoying that these two patches are not naturally interoperable for such a trivial reason. If anyone knows any work arounds, let me know. I am on the brink of finishing a great patch, where this trivial limitation is preventing some great live video manipulations.