The point isn't how much Google spends on stuff in general, it's their wallet. What's important is how much they contribute back to the development of the tools they actively use to fill that wallet.
Kubernetes, Chromium, Android, Go, TensorFlow, Dart, Angular, many more that I can’t recall off the top of my head or ever heard of.
Then all the research they publish, transformer, map reduce, bigtable, spanner, again the list goes on.
I don’t know what companies I’d rate as high as Google in terms of open source contribution and impact. RedHat. Maybe MS and Meta are close.
This being said I would expect they contribute a lot for ffmpeg, which was mentioned explicitly, since this is such a critical building block for them.