Suppose I have a table of 8-digit numbers that I need to add and subtract for various reasons. Do I A: have a child, train them how to read numbers, add, and subtract, and then have the child do it or B: use a calculator purpose built to add and subtract numbers?
Neural nets are always expensive to train. You'd better be getting something from them that you can't get some other way.
Yes, you don't need the machinery of learning when you already have an algorithm you're happy with. Adding a table of numbers, I don't think anyone hopes to do much better than we already do with our circuits and computer architectures.
With video compression, I think most would agree that there might be better architectures/algorithms that we haven't stumbled upon yet. Whether specifically "neural networks" will be the shape of a better architecture, I don't know. But almost surely some meta-algorithm that can try out tons of different parameters/data-pipeline-topologies for something that vaguely resembles h.264 might find something better than h.264.
Neural nets are expensive to train. But so is designing h.264.
Neural nets are always expensive to train. You'd better be getting something from them that you can't get some other way.