[Feature]: MNN for Immich ML — OCR on Rockchip first; optional general backend?

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature I've been aiming to accelerate OCR for Rockchip boards for a while. As I expanded in [OCR hw acceleration for Rockchip boards]( discussion, this is quite cumbersome as NPU (not only rockchip but in general?) cannot really deal with dynamic inputs. Fair amount of engineering needed, and still with corner-cases and reduced quality of output. I've stumbled across "mnn" inference library recently and was intrigued by it's OpenCL / Vulkan support, maturity, activity etc, so I decided to give it a go: it works really well! It worked so well on my rk3588 board, that I started to think if this could also be the "successor" of armnn, or another useful backend even for cpu inference on arm. Below you will find an (agent) structured RFC summarizing my thoughts. Have a look at the performance in the tables below, it&…