Crop Video For Blending

vvvv beta question
1

Hi

I’m trying to make a 8 projection boygroup with 1 server and 4 clients. Each client outputs to two projectors with 1024 x 768 px native resolution.
Between projections theres an overlap of 30 cm (about 100 px from each side).
I have a big video 8192 x 768 and i would like to crop for all the clients.

Should I first crop each video to 1074 (centered) and then shrink it to 1024? Like this:

I was making some blending tests with one computer and it looked fine but now im making the full setup and there seem to be video parts missing.

This means that Soft Edge doesn’t repeat video parts right? So I have to crop the videos a little bit bigger then shrink them back to the native resolution, so I can stretch them back with overlap?

Is this correct?

2

Hi ventolinmono,

If you have 8 projectors with 1024 px width and an overlap about 100px each you get the following

8 x 1024px = 8192 px - 100px (1st Overlap) - 100px (2nd Overlap) - 100px (3rd Overlap) - 100px (4th Overlap) and so forth…

So you will end up with 8 x 1024px = 8192 px - 7 (edge Blend) x 100px = 7492px (real Video size) as the content at the overlap has to be the same on both projectors.

So you get the following

Real Video size = (ProjectorCount x Resolution in px) - ((ProjectorCount - 1) * Overlap in px)

3

Thanks BK

So each video will be 936.5 px width.
936.5*8 = 7492; 7492 + 700 = 8192

4

Well,

not really :-) the Video has to be 1024px each have a look on the picture

each Square is 1024 x 768 but they overlap by 100 px so your overall visible pixel with unique content is 7492 pixel as the content at the overlap is the same in the overlap area.

It’s a good idea to use good test patterns for setting up the crop and the blending.

5

You are right BK. Each part should be cropped from a 7492px width x 768px height composition. In this case a 100 px overlap between videos.

Here is a diagram i made for a comrade that will crop the eight 1024px x 768px videos.

Thank you very much BK.