[mythtv] Swapping from Inerlaced -> Progressive channels "Slow Motion"

[Matthew Moore]

Hi Myth-Devs.

I have asked this question on the user list without success so thought it  
time to bring it to the big-person's list ;-)

In Australia, 576P is classed as "High Definition" and whilst IMHO there  
is little benefit to swapping from the SD resolution of 576i to 576p, I  
really do want the Dolby Digital that is (sparingly) used on these  
broadcasts.

My problem is that if I have been watching an interlaced resolution  
(either 576i or 1080i) then switch to a progressive scan channel, the  
movement looks like slow motion.  Almost like Myth is still expecting an  
interlaced picture so is only showing every second frame.  Audio stays in  
sync and has no quality issues.

If Myth starts on the progressive scan station it works perfectly.   
Recordings also seem to function ok - this seems to be a live-tv only  
problem.

I have previously seen other discussions of my problem around the time of  
the big DVB patch here:   
http://www.gossamer-threads.com/lists/mythtv/dev/104050?search_string=seven%20hd%20slow;#104050   
and my posting to the users list is here:   
http://www.gossamer-threads.com/lists/mythtv/users/187422?search_string=540p;#187422

It has been suggested that I disable deinterlacing, but this doesn't fix  
the problem.  I also know that this isn't Australian-specific as a  
respondant in my previous post has this problem with 720P broadcasts in  
the US.

I'm keen to help debug the problem but have absolutely no idea on where to  
start and what information to capture.

Can anyone suggest where to begin?

TIA,

Matt.