[mythtv-users] MX440/Radeon wars (Was: Hardware ideas)

Jarod Wilson jcw at wilsonet.com
Fri Jun 25 13:25:27 EDT 2004

On Friday 25 June 2004 06:20, Clyde Stubbs wrote:
> On Fri, Jun 25, 2004 at 01:22:41AM -0700, Jarod Wilson wrote:
> > You select a progressive-scan resolution, like 640x480, 800x600 or
> > 1024x768, then the TV encoder scales and interlaces the signal to match
> > the specs you give in XF86Config (such as NTSC & SVideo). You don't
> > specify an interlaced mode to X.
> HAve you actually tried this?

Yes. And ran it on a 27" analog, interlaced-only television for several 

> And how could the tv-encoder (which 
> is a relatively minor bit of logic and analog circuitry) convert
> progressive scan into interlaced? Surely in order to do that it would
> have to buffer half frames.

Dunno the specifics of it, I just know it works.

> Also, if you don't specify an interlaced mode to X (by which I
> presume you mean that XF86Config contains a progressive scan
> modeline or equivalent)


> then how do you tell the 
> TV encoder you want interlacing?

By setting the TV-out options to NTSC (in my case). The NTSC spec is 720x480, 
interlaced. The TV-out encoder then knows to interlace the signal.

> Can you provide an example 
> of how you've done this?

Its been on my web site for ages now, used by quite a few people:

> I'm more than happy to test your 
> claims if you can be a little more specific.

I don't have a PAL-specific config on hand, but change the HorizSync and 
VertRefresh values to match PAL and change the TVStandard to PAL-whichever, 
and you should be in business.

> Simply setting 
> up a 50Hz/31.5kHz 800x600 mode does not produce an interlaced
> signal - I've tried it. It ouputs 31.5kHz progressive scan (and yes,
> I scoped the signal to confirm this).
> This is certainly not how the Radeon TV encoder works, BTW - you
> definitely do specify an interlaced mode in XF86Config.

Didn't know that. Definitely not necessary with nVidia cards. (Though perhaps 
if/when the nvidia driver supports interlaced modes, one could get an even 
crisper picture with perfect interlaced frame timing and not have to use 
Myth's deinterlacer).

> > No, I believe they just use the TV-out encoder the way its intended...
> Well, if you're right I'll take back every alternate half-frame of
> what I've said about the MX440 :-) Please tell me how.


Jarod C. Wilson, RHCE
jcw at wilsonet.com

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