Streaming Purchased Movies in iTunes

https://discussions.apple.com/thread/4120493 You can only stream from a computer using Home Sharing, or from iCloud to an AppleTV.

They don't stream but will start to play before completion of the download once a sufficient buffer is established.

What's a sufficient buffer- I've got close to 90% downloaded and the **** TV show still won't start. iTunes 12.2.1. New MacBook Air. Everytime I click on the movie i get the rainbow wheel of Death.