covert pixels in thermal videos into numbers on temperature in celcius

I have my code which is for social distancing for the person on thermal videos. I am using yolov4 for people detection and created algorithm for measuring and deciding social distancing on thermal videos. i want to add in my code to convert the pixels in the thermal videos into numbers of temperature in Celcius. For each detected person with an enclosed bounding box in the thermal video want to have the highest temperature in this bounding box in the number in calluses instead of thermal pixels