[mythtv-users] vga to component converters

Jason Temple jason at temple.net
Mon Sep 26 18:02:46 UTC 2005


Thanks Cory...I'm checking out the howto's now to see if this is indeed 
the route I want to go.  I'm just looking for 720p for the time being 
(under the assumption that if/when someday I get a tv that can take 
1080i, it'll have vga in), so on-the-cheap is important here.

thanks for the help here!

jas

Cory Papenfuss wrote:

> On Mon, 26 Sep 2005, Erich Boleyn wrote:
>
>>
>> Jason Temple <jason at temple.net> wrote:
>>
>>>     I was wondering what most of you HD guys use to connect your front
>>> end to your tv.  I don't have a fancy flat panel tv with vga imputs
>>> unfortunately, but my Samsung tube can do 720p through it's component
>>> connector.  I've seen a number of converters anywhere from $150-$300
>>> that will take a vga signal and output component...my questions are: 
>>> Are
>>> they any good?  Are there any issues with X (Xorg supports them?  Any
>>> issues with modelines, clocks?).  Are they all pretty much the same?
>>> Although I'm planning to set this up with 720p, I want it to support
>>> 1080i for future sets.  Any input would be greatly apprectiated!
>>
>>
>> I used to use a tube TV which had Component video inputs (still have it,
>> but going to sell it soon when I get my act together) and an Audio
>> Authority 9A60.  The TV supported 480i/p and 1080i, though I had a
>> bear of a time finding a working mode.
>>
>> Here's what I did:
>>  --  NVidia FX 5200 w/2 outputs, one DVI and one VGA.
>>  --  Tube TV is an AdventTV 32" HDTV model.
>>  --  Using NVidia proprietary drivers.
>>  --  1280x960 32-bit color buffer.
>>  --  One putting out 1280x960 @ 75 Hz.
>>  --  One putting out 1280x960 interlaced using this modeline:
>>        ModeLine "1280x960hdtv" 54.540 1280 1424 1480 1616 960 1016 
>> 1032 1124 interlace +hsync +vsync
>>
>> NOTE:  I first tried a 480p mode with no lasting success (it would 
>> glitch
>> regularly, looked like a sync issue), and only after some 
>> experimentation
>> got the 960 interlaced line above working stably.
>>
>     Component is almost exactly the same as RGB on a VGA port.  The 
> only significant difference is that the color has been transformed 
> into YPbPr.  There are a number of schematics and howtos out there on 
> how to build your own transcoder.  If you are too lazy to do that, but 
> one for $100.
>
>     Also, resolutions on digital DV are not nearly as wishy-washy and 
> ill-defined as for analog NTSC/PAL.
>
> 480p :=  720x480   @ 60Hz frame, 60Hz field rate, 31.5kHz Horiz
> 720p :=  1280x720  @ 60Hz frame, 60Hz field rate, 44.9kHz Horiz
> 1080i := 1920x1080 @ 30Hz frame, 60Hz field rate, 33.75kHz Horiz
>
> (e.g. http://videosystems.com/mag/video_getting_tune_dtv/)
>
>     One can quibble about 1080p at 24, 480p at 59.9 Hz, etc, but the above 
> are the de-facto definitions.  Why would someone use a 1280x960 
> modeline to output to a HDTV?  It's not a standard size and barely a 
> standard frequency.  The computer and/or the HDTV will be doing scaling.
>
>     Do yourself a favor... read some of the HOWTOs on modeline 
> generation (e.g. the one in the mythtv wiki that someone copied from 
> one of my previous posts).  Random tweaking of numbers in a modeline 
> is a good way to destroy a monitor/tv.
>
>     In the meantime, may I suggest these as more standard modelines:
>
> Modeline "480i"  14.349 720 760 824 912 480 484 492 525 interlace
> Modeline "480p"  28.698 720 760 824 912 480 484 492 525
> ModeLine "720p" 74.086 1280 1320 1376 1648 720 722 728 750
> ModeLine "1080i" 74.175824 1920 1960 2008 2200 1080 1084 1094 1125 
> interlace
>
>     YES they will have overscan... that's how TV works.  Reducing it 
> in the horizontal dimension is relatively simple.  Reducing it in the 
> vertical dimension violates the standard frequencies or resolutions or 
> both.
>
> -Cory
>
>  --
>
> *************************************************************************
> * Cory Papenfuss                                                        *
> * Electrical Engineering candidate Ph.D. graduate student               *
> * Virginia Polytechnic Institute and State University                   *
> *************************************************************************



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