That's known as cover traffic and is a tactic employed by many of the anonymity oriented overlay networks.

I'll note that any observer already has this problem to the extent that video streams are also encrypted. However most observers presumably recognize the endpoints as well as being able to classify the traffic by means of statistical analysis.

What might be useful would be a tool to generate arbitrary user data of various forms, including HMTL, video, audio, and various message formats. Then it could assemble a convincing traffic stream full of gibberish to exchange with peers at random. You wouldn't even necessarily need all that much of it to overwhelm any would be observers when considered relative to the volume of streaming service traffic that already exists.