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

Bernd Müller caret at gmx.de
Fri Mar 18 14:15:38 UTC 2005


Hello;

First of all: Thank you very much for helping.

Cory Papenfuss schrieb:
>> 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).
> 
>     I have noticed that a large number of video drivers have bugs when 
> it comes to displaying interlaced output.  I once tried to use an ATI 
> card to generate interlaced output on the framebuffer (so I could see 
> the bootup screen).  I ran into limitations of the framebuffer driver on 
> that card (although I can't remember specifically what it was).  I'd bet 
> that's what you're running into... it seems like it should go.
> 
>     One thing you *might* want to try is different combinations of 
> low|high for hsync/vsync/csync.  It sounds like the framebuffer memory 
> is being written correctly, but the field-sync isn't being generated.
> 

o.k  i think i will try this.

>> Yes i know. But what  i've in mind is to enable flicker filtering for
>> the MythTV GUI and disable it for video display.
>>
>     I'm not sure exactly what you're trying to do with multiple heads, 
> etc.  It sounds overly complicated.
> 

Hm, maybe this isn't an idea that is realizable. I thought of enabling and 
disabling flicker filter while X is running.

>> 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?
>>
>     100dpi fonts.  I think MythTV uses the newer vector fonts 
> (TrueType), but I'm not sure.  I don't know if those have a notion of 
> optimal display on interlaced screens.

The TruType fonts dosn't look so bad. Problem are the on lined borders around 
the selection lists in mythmusic and mythvideo. Someone wrote in an other thread 
about simply bluring all images from the mythtv-theme. This works for the 
buttons. But the line around the selection list seems to be generated by mythtv 
itself. So bluring the theme dosn't help.

> 
> 
>     I don't understand exactly why you're using the framebuffer at all.  
> Unless you *really* want to see the console during bootup, can you just 
> wait for X to fire up with the correct timings?  You will have 
> unaccelerated video playing if done via a framebuffer, whereas with X 
> (no framebuffer) you have the potential of using Xv or XvMC.

I don't have to see the console. It would be o.k. for me, if tv-out starts with 
X. But it could be i do not understand the hole thing in the correct way. So 
maybe my postings are a little bit confusing (apart from my very bad english, 
excuse me i'm from germany ;-). Thats how i think of the G400:

- has two heads, first is accelerated and seconed has tv-out but is not
   accelerated
- the original Matrox driver for X supports accelerated first head and tv-out
   on seconed head. Problem is: Not both at the same time, on one head. This
   menas: I wasn't able to get accelerated video on tv.
- workaround: Using the kernel matroxfb which clones first head to seconed head.
   X runs with the original Matrox drivers but with the "UseFBDev" option
   enabled. So i'm not able to use the heads seperately 'cause both heads show
   all the time the same image but i'm able to get accelerated video on tv.

Please note: I'm using the VGA to SCART cabel as described on
http://www.myhtpc.de/showtopic.php?threadid=1214
connected to the seconed head of the G400. (The page is in german but the 
important thing, the circuit, is shown in an image.)

I know about the other VGA to SCART cable as described on
http://www.sput.nl/hardware/tv-x.html
but this didn't worked for me. Maybe i do not exactliy know how to use this with
my G400. Where it will be connected? First head, seconed head? Do i need the 
kernel matroxfb? Which drivers i've to use? Original Matrox or Xorg mga? I 
remember trying to use the G400 without the kernel matroxfb in combination with 
the original Matrox X driver. But i didn't find any modline which was accepted.
Especially the recommended PAL mode
"736x575i" 14.16 736 760 824 904 575 580 585 625 interlace -hsync -vsync
was not accepted.

So many questions. So many howtos i've read. But it's not clear to me how to get 
the perfect tv-out (apart from using DVI with a 2000 EUR plasma tv ;-)

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

(c; bernd

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