2x upscaling without modifying the chroma planes

[JohannesL]

You can encode RGB video currently by doubling the resolution and converting to YV12. The proper way to do this is to pass the chroma planes unmodified, to avoid the issue of resizing the planes twice (upscale, then downscale). This will create video without any chroma bleeding like YV12 creates.

Can Avisynth do this?

[Dark Shikari]

Here's one idea:

chromaclip=clip.PointResize(last.width*2,last.height*2).ConvertToYV12()
lumaclip=clip.ConvertToYV12().NNEDIResize_YV12()

Then take the luma from lumaclip and merge it with the chroma from chromaclip.