[mythtv-users] GeForce2 Card & A Wide Screen TV Via SVideo

Joseph A. Caputo jcaputo1 at comcast.net
Wed Jun 29 21:09:58 UTC 2005

On Wednesday 29 June 2005 16:42, Drew Tomlinson wrote:
> On 6/29/2005 1:10 PM Ijaaz A. Ullah wrote:
> >SVID is only going to give you 640x480.  You can change the screen
> >resolution in myth to something 16:9 and use your tv to stretch the 
> >picture. 
> >But ultimately, it's still 640x480 that's coming out of the TV out on 
> >your 
> >card.
> >  
> >
> OK, thanks for confirming that.  I had read that some cards can give 
> 800x600.  Is there any truth in this?  I know it didn't work for me 
> but  
> I am just wondering.

A very over-simplified explanation:

A standard NTSC TV signal is 480 lines high (well, it's actually a 
little bit more due to VBI data, but it's close enough for the purposes 
of this discussion).  A regular (non-HDTV) television is not capable of 
displaying any more resolution than that.  So, any signal output by 
your video card over composite or s-video must be converted/scaled to 
no more than 480 or so lines.  The difference in the "resolutions" 
supported by any particular TV-out card has to do with what resolutions 
it is capable of encoding into a compliant TV signal.  Most cards will 
do 640x480, since there's virtually no scaling required.  Many cards 
will do 800x600.  Fewer cards will encode a 1024x768 or higher 
resolution, though their number is increasing, I think.

Bottom line, any card that "displays" an 800x600 screen over TV-out 
(composite or s-video) is really just scaling the picture to 640x480 
before sending it over the wire.

(please, nobody call me out for my overly simple explanation... it's not 
meant to be technically detailed.  Feel free to add such detail if you 


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