Split video output

[drumsticksplinter]

Hi,

I’m coming here because I’ve tried Davinci resole and its way too difficult for me to get to grips with.

I need to create a video that is very wide, but to be able to split it into 3 equal parts to export each individual part.

Basically, I have 3 projectors that I’m using to project onto 3 walls in a room. I would like to project moving clouds across all 3 walls. I have 3 medial players that will sync the video content, so need to create the content that can be sent to each media player. In effect it would be like having 3 monitors next to each other and a video playing across all 3

I hope that makes sense.

[Austin]

Let’s say each projector is 1920x1080 resolution.

In Shotcut, create a custom video mode that is 5760x1080. Create your video project as usual from here. You could upscale 4K footage to get the proper width, then crop the top and bottom like cinema projection to get the ultra-wide look.

When done, export it with the Lossless > H.264 export preset to get a manageable file size. If huge file sizes don’t scare you, then feel free to use the Intermediate > DNxHR HQ export preset.

Now in Shotcut, create a new project that is standard 1920x1080. Bring in the video that you exported in the last step. Use the “Crop: Source” filter to crop off the sections outside the current projector’s view. As in, if this is the project for Projector 1, then use “Crop: Source” to crop off the Projector 2 & 3 area. Then export with whatever final export settings you want. Repeat two more times to create crops for the other two projectors.

These last steps could be automated with an FFmpeg script, but that may be overkill.

[PhLo]

I have thought about doing stuff like that in the past - projecting video on the wall for atmospheric effect. Instead of clouds I’ve wished to be able to project stars in a dark room. I’ve looked into all the star projectors on the market, but most use laser grids which look super fake due to recognizable grid patterns.

I don’t necessarily have any solution to offer, just a friendly reply.

I use Shotcut for a semi-similar reason. I’m willing to put in the time to learn DaVinci Resolve, and I use it for some things… but my primary output is 360 video at 5.7K resolution - 5760x2880. The free version of DaVinci Resolve maxes out at 4K resolution, and I don’t want to downscale my footage. I’m not sure what the upper limit is for Shotcut, if there is one. Editing crazy high resolution video is pretty slow though.

How are you planning to get footage that is smoothly stitched at that high of resolution? Are you planning to generate artificial clouds via some software, or do you have huge footage already?

A high resolution 360 camera would be able to capture actual clouds in a panoramic field of view. There are 360 cameras that capture 8K or even 12K video… but I doubt you want to invest in something like that.

Someday I’d like to play around with time lapses with my 360 camera, as the clouds in my videos often look cool over time as they roll across the sky. It’s hard to get high enough above land obstructions to get a really immersive sky recording though - without something like a drone.

Seems like Shotcut can probably do what you need, but the bigger issue might be deciding how to generate super wide cloud footage if you don’t have some to work with already. If you don’t need it to look super realistic you could simply scroll a large textured image like a fractal noise generator or something like that.

I suppose since you are working with projected light, you could have a gradient to black in the 3 overlapping areas, and the light would blend them together on the wall, so the 3 sky projections wouldn’t necessarily have to match perfectly in that sense, depending on how realistic you want it to look. You could even animate the border between the clouds so it’s not an obvious linear gradient.

Software that could generate artificial scrolling clouds for free is Blender. But that’s even harder to learn than DaVinci Resolve in my opinion!

[PhLo]

Austin’s 2-step method of making a higher resolution video and cropping it 3 times seems like a good way to go.

[ConteudoAnimal]

Hello,
let me know if I got your point … for example you have 1h video and want to split in 3 parts of 33m each ? Is it correct ?

If so you can use markers and when export

[drumsticksplinter]

Hi all,

Thanks so much for your replies and helpful friendly advice. It’s all gratefully received.

Austin, thank you! This is exactly what I was looking for I think. I’m brand new to video editing and that method hadn’t occurred to me. I’ll give that a go with some simple content and see if I get promising results.

PhLo, thanks for your helpful advice. I’m not looking for super realistic, the project is intended to be a backdrop for a model layout so a bit or artistic license will be acceptable.

So far in resolve I’ve managed to use some png images with transparent backgrounds and set them to move position slowly along the timeline. The effect is simple, but I think it should work for what I’m hoping to achieve.

ConteudoAnimal, thank you, I’m sure I will need to use this technique at some point also, but it was more about dividing up 1 image size into 3 smaller sizes in terms of pixels rather than in time.

[drumsticksplinter]

I’ve had a go at dividing up the video content today with great success. I used the very wide content I had from resolve and brought that into shotcut. I then used the crop from source filter as suggested and managed to get 3 exported videos that sync a simple moving cloud across them. I had to fluff the output pixel count a little as I was getting thick black margins either side, but I put this down to inexperience in this field.

I’ve not tried this with my projectors just yet, I’m sure there might be issues with where the edges meet up, but I’ve got something to test now at least.

[PhLo]

Awesome. You might try adding a custom Mask From File filter where you gradate the edges of each of the 3 screens so there isn’t a harsh overlap of light on the wall at the intersections. I attached 3 PNGs as example masks that might work if the aspect of each screen is 16x9 or 1080P.

Center Screen

Left Screen

Right Screen

It would be kinda cool to see a still shot photo of your project on the wall or a quick Youtube video upload with phone-shot footage to see your results. Though don’t go out of your way to show it. I’m curious if your projectors are mounted near the ceiling or floor, as this would effect how their angled edges intersect on the wall(s).

Good luck on your project.

[drumsticksplinter]

Hi PhLo,

Thanks for the advice on the mask filter, I will definitely utilise this.

My setup is in a spare bedroom and uses 2 Hitachi ultra short throw projectors mounted from the ceiling. The resolution is quite poor from these : 1024 / 786 as they are data projectors really, used in schools etc, but they are cheap!! I’m trying to prove a concept and then I might invest in some better projectors. They do however have quite good zoom, keystone and shape manipulation features that make setting them up to fit a whole wall quite easy.

There is still some work to do with wiring up the media players, but will get a video of the set up asap

[PhLo]

Wow, 1024x768, a resolution I haven’t heard in a long time!

[Austin]

@drumsticksplinter

1024 / 786 as they are data projectors really

This explains why you saw black bars on the sides of your first experiment. The values I provided assumed 16:9 aspect ratio. 1024x768 is a 4:3 aspect ratio. So, for a three-wide set of projectors, the project resolution should be 3072x768 with an aspect ratio of 4:1.

[drumsticksplinter]

Thanks guys,

I had adjusted the resolution to match my combined projector width 3072 x 768 on my wide video content, but when I used the crop from source filter and cropped 2048 from the right for example, I still had borders. I must have the aspect ratio wrong somewhere else. I think I changed the source to 4000 x 768 in the end to get rid of the black borders.

[Austin]

To make sure I’m understanding right, do black borders appear on the left and right sides when playing a 1024x768 video on your computer monitor? If so, this is expected. Your monitor is likely 16:9 aspect ratio (wide). The projector is 4:3 aspect ratio (square-ish). Displaying a square 4:3 video on a wide 16:9 monitor will leave black bars by nature, just like watching a 1980’s television program on an HDTV screen. But everything should (in theory) look fine when displaying the final 4:3 video on a 4:3 projector.

When you used 4000x768…
(4000 / 3) / 768 = 1.736 aspect ratio (nearly 16:9 or 1.777) for one crop
This will make the video look correct on your computer monitor.
But it won’t look right when displayed on your projector.
This resolution would send 16:9 wide-format video to a 4:3 square-format projector.
The media player would most likely scale the video down to fit, which would leave black bars on the top and bottom when projected onto the wall.