[mythtv-users] [ G400 ] Hotwo enable flicker filters

[Bernd Müller]

Hello;

Cory Papenfuss schrieb:
>> How do i enable any kind of flicker filter to the matroxfb? Picture 
>> quality with mplayer, G400 and the RGB-cable ist fantastic, but any X 
>> appication, especially MythTV GUI flickers terribly. Somwhere in the 
>> web i've read this would be an issue of human optical perception. 
>> Perception of hard edges in GUI's at low frequencies (50Hz) causes the 
>> flickering. So many graphic cards support flicker filters to blur the 
>> image. From the windows driver i know the matrox g400 does to. But i 
>> didn't find anything about flicker filters with the G400 under linux 
>> in web. Does sombebody knows how to enable flicker filters?
>>
>> I'm using the matrox g400 dual max with the kernel matrox framebuffer, 
>> second head connected to tv with the self build VGA to SCART cable.
>>
>     Flicker filtering screws with the picture by definition.  The video 
> being played *IS* interlaced, and should be played interlaced. Flicker

Maybe i could ask you at this point a question of general understanding about 
interlaced video on the second head of the G400: I would like to use a 
framebuffer mode which exactly matches the european PAL standard. I've found in 
  a VDR mailing list the following mode:

mode "768x576-50"
     # D: 14.766 MHz, H: 15.625 kHz, V: 50.001 Hz
     geometry 768 576 768 576 32
     timings 67723 106 1 44 1 70 4
     csync high
     bcast true
     laced true
     accel true
     rgba 8/16,8/8,8/0,8/24
endmode

This defines an interlaced 768x576 mode with 14.76 MHz pixelclock at 50Hz. As 
far as i know, exactly what PAL is defined at. But: If i use this mode i will 
get an skewed image. It's displayed two times (at lower and upper half of tv).
Using the Matrox X driver with framebuffer option enabled it's not possible to 
use this mode for X. With the fbdev X driver it works but also with the skewed 
image. Alternatively i'm using now this mode:

mode "720x576-50"
     # D: 27.949 MHz, H: 34.251 kHz, V: 50.001 Hz
     geometry 720 576 736 576 32
     timings 35780 30 20 65 40 46 4
     bcast true
     rgba 8/16,8/8,8/0,8/24
endmode

This defines a 720x576 mode at 50 Hz, but now with a 27.94 MHz pixelclock and as 
i understand it non-interlaced. This is not what PAL is defined at. But with 
this mode console and X looks very pretty (apart from the flicker problem). My 
question is now: Why do the first mode do not work though it defines exactly PAL 
and the seconed does though it's not PAL. Will the seconed mode will be 
displayed interlaced? I've the assumption that cloning the framebuffer from the 
first head of the G400 to the second is not an exactly one-to-one copy 'cause 
the second head displays always interlaced by hardware definition. It looks to 
me, that the G400 automaticaly generates a PAL image at the seconed head 
independent of what is set to the first head. Cloning the framebuffer means only 
a transfer (copy and scale) of the image from the first to the seconed head but 
the timings will not be cloned. Is the assumption right?

> filters are an artifact of trying to reduce perceived flicker from 
> computer-generated images, but it's horribly bad for maintaining video 
> quality from an interlaced source to interlaced display.

Yes i know. But what i've in mind is to enable flicker filtering for the MythTV 
GUI and disable it for video display.

> 
>     All that's really needed is to make a MythTV theme that has this in 
> mind.  Once upon a time, X11's 100dpi fonts did this by making sure 
> there were no single horizonal lines.  If they were double, the flicker 
> wouldn't be noticed as much.  That's the correct solution (short of 
> using progressive scan TV)

I think the fonts do not make so big problems like the single lined borders of 
the mythvideo or mythmusic gui. A simple workaround is to use very big fonts. So 
there aren't so many single horizontal lines. Maybe there is a workaround for 
the GUI too. Any suggestions?

> 
>      There was some talk awhile back about making such a theme, but I'm 
> not sure how far it got.

Oh, thanks i will look for this thread.

> 
> -Cory
> 
> *************************************************************************
> * Cory Papenfuss                                                        *
> * Electrical Engineering candidate Ph.D. graduate student               *
> * Virginia Polytechnic Institute and State University                   *
> *************************************************************************
> 
> 

(c; bernd
> ------------------------------------------------------------------------
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