Why does my TV out with an AiW7500 blow?

[Wa11y]

I think the title says it all. I'm running XP with the latest drivers for the Radeon All-in-Wonder 7500. I'm hoping the pics will do justice. This is at 800x600, which is the lowest XP will go. I have a hard time reading it, and can usually barely make out what it's telling me.

Now, part of the problem may be the setup I have. My TV is crap, and only has a Coax input on the back. So I run from my Radeon to my receiver via RCA cable and from my receiver to my VCR via RCA, and finally from my VCR to my TV via Coax. None of the cables are above 6 feet long, so it's not an issue there.

But I've also seen the TV out on a GF2 Pro to a 52" TV directly via RCA, and it wasn't too pretty, either. Looked pretty much like this. Any help?

[Wa11y]

And another pic. Hope these can show how crappy it is.

[Aedan]

Sure.

Forget using a TV as a monitor. They just don't have the resolution!

First your chaining of devices, which will definately have an impact on the signal quality. VCRs are noted for their low resolution. RF is noted for its low resolution too. Generally, going straight into the TV in S-video or component  (YUV/RGB) video will give a better picture, but see below first.

Starting with vertical resolution, as this is the closest to the PC equivelent. The good news - an NTSC signal has 525 horizontal lines, of which only 480 are visible. The bad news, it takes two passes of 240 lines to display all 480 lines. TVs are interlaced, PCs are progressive scan.

If your PC horizontal resolution (600 lines) is greater than 480lines, then the video out converter has to find some way of squashing those 600 lines into 480 lines. The net result is that 1.25 lines on the PC end up being 1 line on the TV. 

Now, much more complex, horizontal resolution. I'm not even going to attempt to deal with the horrors that await! Suffice to say, horizonal resolution is about 640pixels. Unfortunately, that's luminance (brightness) resolution. The chromiance (colour) resolution is actually much lower, probably less than 320 pixels across.

If you compare a TV to a monitor directly, field to frame, then your monitor can do 800x600 easily. Your TV is struggling to do 320x240. Comparing frame to frame, your monitor is still at 800x600, but the TV is struggling to do 640x480.

PAL users are better off here, as PAL is a higher resolution signal, at around 768x576.

Now you know why we all use monitors rather than TVs for display!

AidanII

[SteveI]

I've done the same thing with a RAGE VIVO card. Same results. It's not you. As AidanII put it, it's the TV. If you have an Svideo connection to the TV, it should help a bit.

[Aedan]

Ok, I took a picture just to demonstrate how my TV output comes out. The TV is a Philips, and the input is via S-Video (rather than RGB ). The graphics card is a Gainward GF4 based card. The video format in use is PAL-I.

Yes, it looks clearer. That's probably because there's nothing but an 2 metre (6.5foot) s-video cable between the PC and TV.

The strange banding across the picture is due to the interaction between the TV refresh rate and the camera's shutter speed. The moire patterns are a similar effect between the phosphor pitch and other factors. 

  

 

[Wa11y]

Yeah, I knew about chaining devices helping to screw things up, and I knew that NTSC TVs have a really low resolution. But I was hoping there was some way. I got some other answers over at OC with some suggestions, such as increasing the font size, so I may give that a try. This is the computer in my bedroom, and it's specifically for use on that TV. Although I was tempted to find a monitor, and use that instead. But I'll stick with the TV and go from there. Thanks.

[Aedan]

In which case, for NTSC, I'd recommend staying at 640x480! No, I've no idea how you can convince XP that it wants to use that resolution though.

800x600 is pushing it, even with large fonts. I hope your eyes like you very much, cuz they're going to need to be forgiving.

AidanII

[Wa11y]

Originally posted by AidanII
In which case, for NTSC, I'd recommend staying at 640x480! No, I've no idea how you can convince XP that it wants to use that resolution though.

Over at OC I was given the recommendation to change it to 640x480 thusly:

Under WXP: disp.properties>settings>advanced>adapter>list all modes>640*480

I'ma give that a go and see what it does.