[mythtv-users] MacOSX frontend & 1080i

Andrew Gallatin gallatin at cs.duke.edu
Thu Mar 15 15:31:43 UTC 2007


Andrew Kimpton [awk at awkward.org] wrote:
> Todd Ignasiak wrote:
> > On 3/13/07, Andrew Gallatin <gallatin at cs.duke.edu> wrote:
> >
> >   
> >>> Also, I doubt the LCD is being run at 150Hz, where does Myth show
> >>> that?   I think LCDs are set to 60Hz by default, although it's hard to
> >>> tell for sure.   I installed SwitchResX control panel & output the DDC
> >>> data for the display, and it showed it was running 1440x900 @ 60Hz.
> >>>       
> >> It is reported (for me) when using -v playback:
> >> 2007-03-12 09:52:04.014 VideoOutputQuartz::GetRefreshRate() [returning 150]
> >>     
> >
> > Hmm,.   I grep'd my log for that, and it is also returning150.  So, I
> > looked in videoout_quartz.cpp, and it looks like 150 is the value it
> > uses if it doesn't get a valid refresh rate:
> >
> >     // Find the refresh rate of our screen
> >     CFDictionaryRef m;
> >     m = CGDisplayCurrentMode(data->screen);
> >     data->refreshRate = get_float_CF(m, kCGDisplayRefreshRate);
> >     if (data->refreshRate == 0.0)    // LCD display?
> >         data->refreshRate = 150.0;   // Divisible by 25Hz and 30Hz
> >                                                            // to
> > minimise AV sync waiting
> >
> >
> > I'm not sure how that effects playback, but it seems to be the
> > expected behavior for LCDs, and playback is okay on mine.  So, I would
> > guess this is not the issue.
> >   
> I agree - it's not entirely clear what the intent of that 'magic value' 
> is. Remember though that this is only used when CoreGraphics doesn't 
> return a rate - and that only happens for devices such as notebooks and 
> the iMac which have an integral display panel with an entirely digital 
> connection between graphics adaptor and panel. For external LCD Displays 
> connected through a VGA connection kCGDisplayRefreshRate is 'spoofed' to 
> being 60 Hz.
> 
> I think (from dim memory of practical experiments) that changing that 
> 150 value to 60 makes no difference - in fact it may make so little 
> difference that Andrew G's problems won't go away either. But it might 
> be worth a shot for someone to change it and repeat the build.
> 

For what it is worth, I changed it from 150 to 60, and my problems
went away and I have smooth playback for 1080i.  Perhaps 150 is
violating some other assumption which Myth is making?

Drew






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