The current system is a separate neural network running against every frame of every one of the 8 cameras. The new one is what elon calls the "4D" image process

The current system is a separate neural network running against every frame of every one of the 8 cameras. The new one is what elon calls the "4D" image processing. It uses all cameras to create a composite 3d representation where the 4th dimension is time. One of the things they use this for is to predict where an object will be in the future.