Created attachment 157290 [details] [review]
Proposed patch

When progressively downloading a movie it should still be possible to seek past the end of the download part of the movie. For example i might only want to watch the second half of something. Proposed patch attached.

Unfortunately this doesn't seem to work too well with gstreamer.. Purely seeking forwards works perfectly, but when seeking backwards again to a part that was never downloaded seems to break things (playing never starts).. 

A little ascii ``art'' to make things more clear. Say the progressive download got to point A in the timeline below, then seeking to point B works fine, but afterwards seeking to a point between A and B and gst gets unhappy and stops the playing (and doesn't seem to download any further)
+++++A--------------B+++++

This patch also makes the decision whether or not to start playing take the current position into account. What's still missing is logic to pause the pipeline again if needed