Webm header data

[Lee Matthews]

Hi,

I'm streaming vp8 video using the webm container. I also wish to be able to start/stop recording the video at a given point. I have a tee element after the webmmux element and I add a branch (queue ! filesink) dynamically. It is saving data, but it appears to be missing the webm header information and the resulting file is not playing. 

Does anyone know how is it possible to obtain the webm header data at a random point in the video stream ?

Thanks
Lee