is PRE videoplayer (and web broweser) able to play http MP4 stream without downloading?

I'm trying to adjust mythweb to be able play mythtv recordings. Getting mp4 exposed is fairly simple process. However when videoplayer is invoked it starts ti "spin" and nothing happens...
Maybe it tries to download before playing which is no go for most recordings (GBytes over wifi is not good idea). Is there a way to force immediate start of video?

I have also tried to insert html 5 video tag into webpage - it shows black rectangle of video size but thats all...

Anybody has a hint? Developer documentation at palm website does not have much info.