Did you ever figure this out? I am having the same problem. I wonder if it is the version of the SDK that I am using. I am currently locked into a hacked version of v3.1 of the SDK.
I see these two errors when I try to embed the video.
'/assets/video/SearchTutorial.f4v' does not have a recognized extension, and a mimeType was not provided
Unable to transcode /assets/video/SearchTutorial.f4v.
f4v files should work in the old MX VideoDisplay as well as the new Spark VideoDisplay/VideoPlayer components. Here's an example that works for me:
Perhaps you're pointing to the file/stream incorrectly.
There were a couple of problems with my code. The main issue, as you guessed, was the way I was referencing the asset on the local file system.