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

[Peter van Gils]

Hi Bernd,

Just a tip: you can save some money next time you need such
a cable. I use Cat5 UTP for a 13m VGA cable and it works
great! (Running 1024x600 @ 60Hz on a 32" LCD.)
You have to keep signal and ground together in one
twisted pair and add 22 ohm resistors in series with
the signal wires at the TV end. (The resistors are
needed to prevent ghost images.) The shell is left unconnected.

My $0.02.

Peter.

Bernd Müller wrote:

> Hello;
>
> O.k. i will try the cable like this:
>
>      VGA                                          SCART
>
>     1 -O------------------------------------------O- 15 R
>     6 -O------------------------------------------O- 13 R Gnd
>
>     2 -O------------------------------------------O- 11 G
>     7 -O------------------------------------------O-  9 G Gnd
>
>     3 -O------------------------------------------O-  7 B
>     8 -O------------------------------------------O-  5 B Gnd
>
>    13 -O------------------------------------------O- 20 csync
>    10 -O------------------------------------------O- 17 csync Gnd
>
> shell -O------------------------------------------O- shell
>
> The bridge between PIN 5 and 11 was described as "The link between 5 
> (Gnd) and 11 (Mid0) tells your VGA card that your `monitor' is 
> colour". But i will omit it.
>
> Making the cable as short as possible, is a little bit difficult in my 
> case. My MythTV Box and the tv are in different rooms. The minimal 
> cablelength i need is 8 meters (~ 26 ft). I do this as a due to noise 
> reduction. I know that this i very problematic. To keep the loss as 
> minimal as possible i'm using a special RGB cable. Each of the 5 wires 
> is shielded, this means is coaxial. Additionally the whole cable is 
> also shielded, too. My electronic dealer advertises it as "High 
> Quality Monitorcable. 5x 75 Ohm coaxial  single and overall 
> shielding". I did not find any better shielded (and even more 
> expensive ;-) cable for this task. So i'm in hope i will work for me.
>
> Wow, it's really amazing. I've read so many tutorials about tv-out and 
> the G400. But in no one i've read about this type of cable. I think, 
> if it will work for me, i will write a small howto about it.
>
> (c; bernd
>
> Cory Papenfuss schrieb:
>
>>> VGA                                                SCART
>>>
>>>   1 -O------------------------------------------O- 15 R
>>>   2 -O------------------------------------------O- 11 G
>>>   3 -O------------------------------------------O-  7 B
>>
>>
>>
>>     RGB signals, yes
>>
>>>
>>>   6 -O------------------------------------------O- 13 R Gnd
>>>   7 -O------------------------------------------O-  9 G Gnd
>>>   8 -O------------------------------------------O-  5 B Gnd
>>>
>>     RGB grounds, yes.
>>
>>     If possible, keep these lines as short/clean as possible, and do 
>> not connect all the grounds together anywhere.  You may even try to 
>> use coaxial cable or something for them.  This is pretty high 
>> frequency (although not nearly has high as for a computer signal).
>>
>>
>>>   5 -O-+
>>>        |
>>>  11 -O-+
>>>
>>     I don't know what this is for... it might be a matrox-ism.All I 
>> see is Ground and No Connect, so I wouldn't do it if you want to make 
>> a generic VGA cable.
>>
>>
>>>  10 -O------------------------------------------O- 17
>>> Gnd
>>
>>
>>
>>     Sync GND, yes.
>>
>>>
>>>  14 -O------------------------+
>>> -VS                           |
>>>                               |
>>>  13 -O------------------------+-----------------o- 20
>>> -HS                                               -CS
>>>
>>     Here's what you probably don't want to do.  Connecting VGA HSYNC 
>> and VSYNC together like that means they'll try to drive each other. 
>> That's what the transistor circuit is for.  Generally, if a video 
>> card supports CSYNC, it'll come out on the HSYNC pin.  So, just 
>> connect VGA13->SCART20 and leave VGA14 unconnected.
>>
>>> 5,6,7,8,Shell ------------------------------------ 5,9,13,17,21,Shell
>>>
>>
>>     I wouldn't run the video GNDs to the shell.  Leave them 
>> point-to-point.
>>
>>
>>> Doing the math for the geometry and the timings should be no 
>>> problem. The thing i'm not clear about is what the flags csync, 
>>> hsync, vsync, bcast and so an are to be used for. At this point I 
>>> would understand if you say RTFM  and i will do, but maybe you can 
>>> wrote some words in general. I know what the hsync and vsync signals 
>>> are for. But what will the options in the XF86Config modline will do?
>>> A simple enable/disable?
>>>
>>
>>     The syncs can be either polarity... nominally 0 and then 5v 
>> (+Xsync) when triggered, or nominally 5v and 0 (-Xsync) for trigger 
>> (X = h|v|c).  The flags just control their polarity.  The csync flag 
>> tells a supported card to put out *BOTH* HSYNC and VSYNC out the 
>> HSYNC wire (XOR'd I believe).  The bcast is a framebuffer-specific 
>> option that I don't think many/any cards actually support.
>>
>>     The hsync/vsync flags in the modeline don't enable/disable 
>> them... just change the polarity.  The lack of those options just 
>> mean default (+ I think).
>>
>> -Cory
>>
>> ************************************************************************* 
>>
>> * Cory 
>> Papenfuss                                                        *
>> * Electrical Engineering candidate Ph.D. graduate 
>> student               *
>> * Virginia Polytechnic Institute and State 
>> University                   *
>> ************************************************************************* 
>>
>>
>>
>> ------------------------------------------------------------------------
>>
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