Here we go , hdmi capture from 5d2 found some very interesting results .
I explored reg C0F14254 while the HDMI connected to my aja capture card , switching from 1080i to 480p(VGA) and I never thought i see the results i did .
So first connected HDMI in 3x3 1080i mode then enabled the "Force HDMI->VGA"(480p mode) and got this

720p 59.94 in 480p(VGA mode) ? , there was no image i could see but when went from 1080i to 480p while capturing hdmi i got this

look like canon is sending multiplies image streams in the So called "VGA/480p" but really 720p60 mode , I suspect the green image is the vga stream .
Here a link to the prores 422lt file
5d2_switching-hdmi-1080-480.mov to be viewed or downloaded for the above image
https://drive.google.com/file/d/1tJ5N7mhiL0_dz1h5Cu4BDnW0io44Hn0U/view?usp=sharingThat not even the strange thing , I found how to toggle the HDMI between Interlace & progressive scan mode , so 1080i & 1080p
Left side Interlace 1080i Right side progressive scan 1080p

Changed C0F14254 0x32090232 ->0x32090231

Crop off the bottom of frame and you get 1920x518 then resize the frame to 1920x1036
Link to my google drive to view or download for
5d2_c0f14254_2x_vertical.mov prores 422lt just a few seconds for the above image
https://drive.google.com/file/d/1BdvEgmLxIhibAhyGflRq1jZ71ZP7qukW/view?usp=sharingFull size frame for above 1920x518
5d2_c0f14254_1920x518.pngAnd the full size stretched frame 1920x1036
5d2_2x1_1920x1037.pngAnd the vertical is 2x stretch , I think it's removing one of the interlace fields which be like line skipping in a way
to progressive scan , but it should be doing a 2:1 pulldown (2 interlace fields in to 1 progressive frame) to stop it from compressing the vertical .
The 1080p stretch vertically is as good if not better then the interlace frame to my eye , maybe even less aliasing ?
This will help me with the hdmi in crop_rec for sure.