I am getting a proxy yellow line at the top of my timeline. I know what red means - needs rendering, but what does yellow mean and how do you render that? I tried to render, but nothing happens. And there's nothing in the index of the massive books about it. Why has caused the yellow proxy line?
Stumbled across this while looking for the answer to a different question, and thought I'd take time to reply, even though OP probably won't still be looking for the answer four years later. Anyway, my guess is that you're using the shortcut CMD+R to render, which renders only audio and video. What you need to do to render the proxy is hit OPTION+R or go Sequence>Render All>Both.