Do not see Speed Index metric on test results

I have poured through the documentation and forums but can’t find anything on this. When I run a test through web interface, I do not see the Speed Index on the metrics: http://www.webpagetest.org/result/120921_FH_JRS/

But on other public tests I do see it: http://www.webpagetest.org/result/120920_69_8F0/

Is there something in the setup?

Any help much appreciated!

Kevin

Speed Index is only calculated when Video is captured.

Works great. Thanks!