I would tend to say that neither of those two versions are what I would expect from an interlaced slide transition, although the single image you uploaded earlier looked closer. The "Camera 1" image which is moving across the screen should be visibly broken into two interlaced halves (ie Fields), since the horizontal position changes from one field to the next.

vMix certainly sets the NDI Output frames to be identified as Interlaced (when the Master Frame Rate is interlaced), but you should also take into account what NewTek's NDI Monitor might be doing when decoding and displaying interlaced video. My guess is that it's doing both simple-scaling and blended-deinlerlacing, but not necessarily in the best order, hence the unnatural interlace-derived artefacting that you're seeing (on anything that isn't displayed exactly 1:1).

I'm not a dev at NewTek, I don't know the interworkings of how some stuff is coded.

I agree with what ZenVideo is saying. In both example images, you are seeing different types of processing to deal with interlace video.

The NDI Monitor output looks like a scaling issue since you aren't viewing the image on a 1:1 display. The interlace lines get blended together (usually with some weighting) which is causing the artifacts you are seeing. But the original image is fine, this is a display scaling issue.

The vMix output looks like they are displaying a single field since there is no interlace at all displayed in the image. Probably using line doubling to keep the correct video aspect ratio. Again I'm sure the original image is good, just a display issue.

I think the short answer is that interlace is being handled correctly, internally, just that viewing interlace images on a progressive display is difficult. There are other options to remove interlace like motion detection, but that can't be done in real-time or they introduce a high amount of latency. Luckily with 4K we can finally put an end to interlace!

Kane Peterson
NewTek