[mythtv] Idea for interlaced playback.

[Bjørn Konestabo]

Dennis Tell wrote:

> I'm using a cheap msi fx5200 svideo out and it works with a 25hz 
> 720x576 output. I've attached my xorg.conf file if you'd like to try 
> it. I have deinterlacing turned off in mythtv, and am using opengl 
> sync. I have flicker filter and overscan set to 0 in nvidia-settings.

Thanks. The file "worked" in the sense that X started, and looking at 
the modeline numbers I would be expecting to get 25Hz, but I'm not.
Running glxgears reveals that opengl still synchs to 50Hz. My card is an 
aopen and I'm using the 7676 driver. We could have
different tv-out chips I suppose. For instance, my correct overscan 
setting is "25". Setting it to "0" gives me a tiny picture with large black
borders..

> However, I'm using dvb-t, so if your problems are a result of your 
> analog capture card this might be of no help to you.

I do not think it's because of analog capture. It appears to be a 
playback only issue. I can watch a clip just fine, then skip back 10 seconds
and watch it again, this time with the even and odd fields reversed. Or 
I can mis/re-align the fields simply by pausing and unpausing.

What's happening is that the video refresh is at 50Hz, and the 
framebuffer is updated every 2nd refresh with two new fields.
Sometimes this is out of synch with the tv-out which causes fields to be 
shown out of order.
(Both fields being refreshed in the framebuffer and the TV-out has only 
displayed one of them).

This is why I would like a playback option which updates at 50Hz, but 
only updates one of the interlaced fields at a time. Unfortunately this is
harder than I had hoped. I'd also get an audio offset as I would have to 
buffer at least one field pair.

I've searched both myth-dev and myth-user and the web pretty thoroughly 
trying to find a solution to this problem, but I've only found out that
quite a few people share exactly my problem. Sigh. I really should get 
myself an HDTV and swap this problem for a set of new ones. :)