[mythtv-users] Configuring XFree86 for TV out
Cory Papenfuss
papenfuss at juneau.me.vt.edu
Sun Aug 15 09:44:22 EDT 2004
On Sat, 14 Aug 2004, Shaun Jackman wrote:
> Hello,
>
> I have a Matrox G550 I'm attempting to configure for TV out. So, a
> couple questions...
>
> 1. What's the the best display mode for NTSC output?
>
> How many vertical lines does NTSC really have anyways? Can I set up a
> display mode for the NTSC television's actual native resolution?
>
With a normal TVout card, you probably can't. Searching online found
this as "standard VGA 640x480 at 60Hz"
Modeline "640x480" 25.17 640 656 752 800 480 491 493 524 -hsync -vsync
I would venture to say that short of building the monstrosity that I did to
make sure it's standard, running a 720x480 mode at NTSC frequencies (480p, not
480i since VGA monitor or your eyes won't like it) would yield something like
this found online:
ModeLine "NTSC-DVD-59.94p" 27.0 720 736 800 858 480 484 492 525
That gives 27e6/858 = 31.468 kHz = 2 * 15.734 kHz horizonally
31468/525 = 59.94 Hz vertically
If you don't like 60Hz on your monitor, you could try 3x
ModeLine "NTSC-DVD-89.91p" 40.5 720 736 800 858 480 484 492 525
47.203 kHz horiz
89.91 Hz vert
... or 4x
ModeLine "NTSC-DVD-119.9p" 54.0 720 736 800 858 480 484 492 525
62.937 kHz horiz
119.9 Hz vert
Like I said, you're kinda fooling yourself since the video card is
doing a scanline conversion anyway down to 480i. These modes just give it a
nice multiple of the scan rate (to exacerbate any beat frequencies since
nothing is genlocked... :).
-Cory
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