[mythtv-users] MacOSX frontend & 1080i

Andrew Gallatin gallatin at cs.duke.edu
Thu Mar 15 20:48:04 UTC 2007


Todd Ignasiak [ignasiak at gmail.com] wrote:
> On 3/15/07, Andrew Gallatin <gallatin at cs.duke.edu> wrote:
> > 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?
> 
> So, now with the value set at 60, 1080i playback is smooth on your
> iMac's internal display?  And it doesn't require any interlace
> detection override or other unusual setting?

Everything is as good now on the internal display as it was on the
external 1600x1200 LCD.  It still requires manual interlace setting,
but this is normal for this station, and happens when I run my old,
pre-built binary on an external 1600x1200 lcd (which reports 60Hz).
When I use my Linux frontend, it says the same thing (I just never
noticed, because I had been running the Linux box at 1080i output w/o
any deinterlace enabled).

As I said before, there has always been something weird about this
station.  Perfect 60 minute recordings always appear to Myth as being
52 minutes long.  This is WRAL, which is a pioneer in HD, and was one
of the first HD stations in the country.  They may be doing something
cutting edge,  that Myth wouldn't see elsewhere.

Drew


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