What more do you want? Do you want the writers of the Bible to give you God's Social Security Number, or His driver's liscense number. Maybe if I showed you a picture of the light shining down with a nametag on it saying, "Hello, my name is God." I mean, it's a bright light, too brilliant for human eyes to look at, shining down from the heavens (and it wasn't the sun, either), a dove (one of God's symbols, as it was used to show Noah that the flood was over) came down and landed on Jesus, and a loud, booming voice from heaven said, "This is my son, in whom I am well pleased." That's about as clear cut as it gets. The best you're gonna get is that every time in the New Testament that an angel spoke to somebody, it is specified that it wass, in fact, and angel speaking. When God appears, there's a bright light that nobody could look at, because God is too brilliant for human eyes to see, as was described in this passage. Nowhere in the Bible is anyone other than God described as being that brilliant, not even Jesus. I'm betting the reason they didn't write down that it was God is because they assumed everyone had already figured that out, and that it wasn't necessary to state it.