I've started investigating what's causing this. First thing I've found is that if I use a SmoothStreamingMediaElement from SmoothStreamingClient v1.5, then media starts playing after just 3 or 4 seconds. And in fact you can set the BufferingTime property
of the SmoothStreamingMediaElement to 1 second and media starts playing after just 1 second.
So it must be the MMP:PF that is causing the media to also start after 10 seconds. I'm starting to have a look at the MMP:PF source to find out what's going on, will post if I find out what's causing this.
In a separate but possibly related issue, I've also noticed if you use MMP:PF v2.5 to create a Silverlight app and host this app on an IIS box with Basic Authentication turned on, and then open this in Chrome or Firefox you are asked to authenticate
twice. Once for getting the webpage then again when trying to fetch the manifest for the smooth stream I want to play. This didn't happen when using smf v2.1, it only asked to authenticate when getting the initial webpage.