[vdr] Re: More thoughts on Matrox TV out with interlaced programmes

[Mark Watson <linuxtv@foft.fsnet.co.uk>]

On Thursday 03 February 2005 23:24, Tony Houghton wrote:
> In <200502032112.47331.linuxtv@foft.fsnet.co.uk>, Mark Watson wrote:
> > That said if it doesn't happen often that might not look so bad.
> > Thoughts? Might be easiest to change the hardware clock on the card to a
> > PAL frequency one!
>
> The problem isn't whether the card can generate the correct frequency,
> but whether it can be kept in sync with the broadcast, or if not,
> whether both the graphics card's and broadcaster's clocks are close
> enough to an exact 50Hz for frame skips and repeats to be tolerably
> rare. I don't believe the former is possible, but having played with
> mplayer dvb:// for a little while it looks like the latter is the case,
> because I didn't notice any jumps in a few minutes.

Oh I see since even if both using PALs official clocks there will probably be 
a slight different still (depending on tolerance of clocks...). So you'd want 
to dynamically adjust the clock on the Matrox to match the broadcast. I doubt 
reprogramming the clock on the fly is possible since it will lose sync 
temporarily. Changing the picture size (i.e. vtotal) on the fly should be 
though. i.e. Run the clock slightly slow (49.9Hz) and occasionally skip the 
final few lines to give a slightly faster frame to keep it in sync. 

Thanks,

Mark