Swapping left view in MVC file with 4K?

[ike]

Hey all, apologies if this is a newbie question that is easily shut down.

I rip a lot of 3D Blu-Rays using MakeMKV and BD3D2MK3D so I can watch them in a VR headset. I also occasionally rip 4K UHD 2D discs.

It's my understanding that the MVC format stores the full image for the left view, and then stores the right view in a compressed format that essentially just describes the way in which the right view differs from the left view.

Would it be possible to take a 1080p MVC file and swap out the left view AVC stream with a 4K version of the same movie? (Assuming the left view in the 3D version perfectly aligns with the 2D version of the movie). The left view would be fully "upscaled" to 4K, and the right view would be mostly upscaled. Obviously it wouldn't be perfect. Any sharp edges between 3D layers wouldn't be as crisp, and of course the extra visual information revealed by parallax shifts would still be 1080p. But, for the most part, the image quality would be greatly increased.

Since no one has done this before (as far as I can tell), I'm assuming I'm misunderstanding something big. But is there really any reason why this wouldn't be possible? Does anyone know of any software/tools that could be used to attempt this?

Thanks!

[ike]

I've been reading up on MVC, SSIF, etc. I overlooked the fact that the delta H.264 file for the right eye would need to be manually upscaled to 3840 x 2160, in order for it to align properly with the 2D 4K movie, but simple interpolation like Nearest Neighbor should be fine. I'm not sure if this can be done to the delta stream alone, though, so I'm thinking I could use BD3D2MK3D (CRF 0) to losslessly extract the full left and right frames, manually enlarge both, and then use DVDFab MVC Codecs to encode back into SSIF/M2TS? Is that crazy? Will DVDFab even allow the creation of a 3840 x 2160 SSIF?

From there I'm a bit stuck with my current knowledge. It looks like it's possible to use FFMPEG to convert the true 4K 2D movie from MKV to M2TS. If I open up the /BDMV/STREAM folder (that I'm assuming I can get from the DVDFab result, unless I'm misunderstanding), and simply swap out the left M2TS in that folder with the new 4K M2TS, then perhaps this modified ISO could be sent back to BD3D2MK3D in order to generate the new right eye view (as part of the full-SBS MKV)?

Please let me know if anyone has any thoughts. I'm diving headfirst into something I don't have much prior experience with.