I'm new to vMix, encountering a problem that may be incredibly easy to solve, but a search in the forums didn't yield any answers yet.

Here's the scenario. I have a 1080p vMix document. I insert a 4K image source into the document, which obviously gets scaled down to the working resolution. The problem is, the image doesn't scale down gracefully. The quality of the image degrades heavily and the output looks terrible. (especially any text in the image) Now, if I resize the 4K image down to 1920x1080 in Photoshop, and import it into vMix, it displays properly in the high quality I would expect. The text looks smooth and anti-aliased just like in the original, the colors and gradients are right. Everything looks good. The same thing happens to me with video, and it's really awful with PowerPoint presentations. (again, text in the video looks especially bad) Also, this degradation in quality shows up in preview window, live window, fullscreen, and the recorded output.

So you might be inclined to say, "Hey stupid, just make sure your assets are the same resolution as your vMix document." which I would agree with you if all the images were going to be fullscreen images. But that's not going to work for some of the picture-in-picture / interview / presenter and presentation scenarios that make up my workflow. In these scenarios, some images and video will have to be scaled in order to fit it properly on the screen in a nice arrangement. The problem is, any scaling seems to ruin the quality of the source material when scaled in vMix.

I can try and combat this by creating as many assets as I can in a resolution that would display well natively without vMix scaling the source, but the problem is, there are some sources in my workflow where that isn't possible.

So, to get to the point. Am I missing a simple setting that improves the way input sources are scaled in vMix? Is there something I can do to my vMix document settings to make this problem go away? Or do I need to just make as many assets as possible the perfect size to display natively, and then just live with the fact that any content that has to be scaled will not look good?

I'll provide 1 of the images that I was using. This image serves as a background for a Multi View input. Both images come from the same 1080p vMix document. The only difference is that one image is natively a 4K image, and the other is natively a 1080p image. If you do a stare and compare on both images, you'll see that the text, and some of the gradients are noticeably worse in the image with the scaled down 4K image.

@mjgraves, I'm in total agreement with you in regards to the things I can control. The assets that I control, I can create at a resolution where no scaling is necessary. However, some of the assets I'm not in control of their size/resolution, and this problem is also happening with video sources. I guess to be more proper, it's a camera source, but it's actually a PowerPoint presentation being fed into vMix via HDMI capture. It comes in at 1080p and there's nothing I can do to change that. (there's other hardware in the device chain that depends on that source staying 1080p) And to get it to fit my workflow, I have to scale that source so I can use it in a side-by-side shot with the speaker giving the presentation which all sits in front of that background that I uploaded to demonstrate the scaling issue. When I scale the camera source, the quality suffers in the same manner as the example images I provided.

If I just import the PowerPoint presentation into vMix, I lose the antialiased text, animations, and transitions that some of my presenters utilize, and I still have to scale it. And if I export the presentation as images, I still lose all those things, but can resize it in Photoshop so that vMix doesn't make it look any worse via scaling, but I still lose all the things I want to retain in the video. And then someone has to keep track of the slide advances to make sure that they stay in time with with the live presentation feed.

So, I'm totally with you, use the right resolution for the assets I can do that with, but I'm still looking for a solution to the ones I can't change. I've used other video switching software platforms, and have not run into this issue before. So it's kind of caught be by surprise that vMix can't scale large sources down and still have them look nice. I'd completely understand if you were scaling up a small source to a larger size. Of course that's going to look bad, but I would've hoped that scaling large sources down would have looked fine, and possibly had effectively antialiased the source while displaying it at the smaller size similar to the way video cards implement super-sampled antialiasing in video games.

@admin, you said that you made a previous post that was in error in your most recent post. However, I only see one post from you. So I don't see a post previous to reference to that one that would be the one that was in error. Perhaps I'm missing something. It wouldn't be the first time.

In regards to the 4K image not being the right size. It is the right size. The point was to show the effect of vMix scaling a larger image down to 1080p. So the 4K source image is supposed to be scaled down to 1080p by vMix. So you should have 2 images to compare. One that was originally 1080p and imported to vMix, and the other originally 4K, and scaled down to 1080p by vMix. They should both be effectively the same size, but you can see that the image that was 4K source does not look nearly as good as the 1080p source. Both images were captured from a vMix live output.

I use BoinxTV/mimoLive at work. I'll have to see if I can get you some comparison images from that. Not sure if I'll even have time to fire that computer up today though. I could also see about firing up OBS Studio when I get home tonight.

I deleted my first reply due to the incorrect info, sorry about that.
What I was looking for is the original 4k image so I can run some scaling tests in vMix and see how it compares.

vMix uses Linear Interpolation for image scaling for reference, which is used by most live video software I have tested.

When the signal comes from HDMI, I guess it is supposed to be video anyway, not graphics

Just to be clear, I only wanted to reply to mjgraves, himself replying to Martin from vMix, that when a signal is coming from HDMI it is considered by vMix as a video signal. Thus Linear Interpolation is used. I agree Bicubic Interpolation gives better results for graphics but I guess vMix can't distinguish what's coming in via HDMI, whether it's pure video or graphics converted to video.

So my intention was not to say that the signal SHOULD BE video and not graphics. I was trying to express that, HDMI being used, there is no way for vMix to change and optimize its interpolation method.

Bien à vous tous,
Guillaume

Slightly off-topic, but I just wanted to remind about that some of us have in other topics pointed out the not so good scaling when images are rotated. Primarily noted for lines (as a graphical element) in images used for for example in Virtual sets.
Thanks.

I've researched this a bit more, and it looks like vMix may not be scaling 4K to HD correctly even taking into account the difference between Linear Interpolation
vs Bicubic.

I confirmed this by scaling a 4K image to HD using linear manually and then comparing, so we'll try to get this fix put in the next update.

Thanks,

Martin
vMix

To be specific, the fix will help in situations where you are scaling down an image by exactly half.
For example 4K to HD, or two side by side 1080p boxes within a 1080p output, so it should help with the scenarios you mentioned.