Not talking toddler

My 15 month old son doesn’t say things like “Mama” or “dada”. He can say different sounds but he doesn’t know what it means. He also doesn’t point or wave. He will reach for things though. He interacts well but he doesn’t respond when you call his name (he’s not deaf. He chooses to ignore people), he doesn’t express himself except through screaming. I have tried talking to him and working with him but he gets frustrated and I don’t know what else to do. Is he still to little to be concerned? Is this normal?