Any way to find out what the CRF of an encode WOULD have been?

[benwaggoner]

So, encoding with CRF is essentially same as encoding 2-pass ABR at the same bitrate as the CRF would have produced. So, emulating a CRF encoding as ABR is straightforward.

But how about the reverse scenario: taking an ABR encode and figuring out what CRF would have produced a file the same frame size?

Given that CRF is used in internal rate control, I imagine that there is some sort of CRF value calculated for each frame. True? If so, is there any way to log those values? That would be a good start (and useful for other scenarios; per-frame CRF would be a better quick quality heuristic than per-frame PSNR or SSIM!).

Is there some sort of target CRF generated by the first pass that could also be captured?