Widescreen SDTV Output using an NVidia Chipset

Posted by Paul on 29th January 2005

First off, the point of this blog entry is to work through some of the unresolved difficulties I’ve had in trying to output a correctly sized display to a widescreen Standard Definition TV (as I’m in the UK the TV is compatible with PAL-I).

Now here’s the specification for the video card that I currently have installed in my Windows XP Pro-based PVR system:

  • XpertVision GeForce4 MX4000.
  • NVidia’s own integrated MV chip for TV/s-video output.

I’ve also tried a video card with more recent, and higher specification, NVidia chipset:

  • XFX GeForce FX5200 AGP 8x Graphics Card with 128MB DDR memory and TV-Out.

Again, this card uses the same NVidia integrated MV chip for TV/S-Video out, with the exact same level of configurability and problems, which I discuss below.

Generally the problem I’ve experienced with these NVidia cards is one of outputting an image with the correct aspect ratio to a widescreen (16:9) Standard Definition (SD) TV, through the card’s S-Video output port. More specifically, the facility to create custom resolutions for display using any and all of the published NVidia drivers is buggy; at least when used with an NVidia MV chip.

All the built-in standard resolutions, provided by the NVidia drivers, produce a correctly sized standard 4:3 resolution. I can determine this because of the way my widescreen SDTV can almost perfectly zoom those standard 4:3 resolutions – the zoom function is provided by most widescreen TVs, to allow 4:3 broadcasts to fill the whole of the 16:9 screen. But custom resolutions that are created to give a natural fit on a widescreen SDTV display (i.e. without recourse to zooming) result in an incorrectly sized image – resulting in a scrolling/panning Windows desktop or the desktop being hugely oversized (far too much for the TV’s zoom control to correct). There are three possible causes that I am aware of:

  1. Custom resolutions just don’t create the correct timings to produce an appropriately sized image.
  2. The burst of widescreen data inserted at the start of scan line 23 for Wide Screen Signalling (WSS) transmissions is absent, creating an incorrectly sized image.
  3. Both 1. and 2.

Given what I’ve read about NVidia’s integrated MV chip, I’m inclined to believe there is a complete lack of support for widescreen SDTV. Before NVidia started integrating their own TV-out support into the main graphics chipset, card manufacturers had to use third party chips. A popular chip is the Connexant CX25871, which is considered to be amongst the best for have one of the best for TV output.

I’ve also tried using an ATI Radeon 9600SE with poor results. Problems with this cards included:

  • No resolution for widescreen SDTV (e.g. 720×400, 800×450). Only higher resolutions were catered for.
  • very poor TV picture quality, producing unreadable text on screen. The effects were blurred images and text with text particularly shaky. This even occured during computer start-up – something that was never an issue with the NVidia MX4000.

Here‘s a good article for geforce4mx video cards and tv. The 16:9 display ratio of widescreen provides a resolution of 1024×576 pixels. The horizontal refresh is an interlaced 60Hz.

Question – Widescreen TV

I’m having difficulties fitting the display correctly on my 28″ CRT widescreen TV (a Toshiba 28w93b). All of the resolutions I have tried, including 1024 x 576, either result in much of the picture being off the screen or the aspect ratio being wrong. My graphics card is a XpertVision GeForce4 MX4000 with its s-video output hooked up to my TV. I’m using the latest NVidia device drivers (version 71.84).

To make things worse the NVidia drivers appears to contain a number of bugs associated with setting the resolution on s-video output, as different dimentioning results from setting the resolution from the three different available locations!

Posted above question to alt.comp.periphs.videocards.nvidia with subject “widescreen tv”

Question – Aspect Ratio Problems

I’m using a NVidia GeForce4 MX 4000, with a custom resolution of 1024 x 576, to display to a TV (a widescreen CRT) through the S-Video port. Problem is, it displays using a 4:3 aspect ratio, giving black bands at either side of the 16:9 display! The full width of the display can be scrolled into view by moving the mouse cursor off to the left or the right of the screen.

Can anyone tell me how I can set up the NVidia driver with the correct display width, please? I suspect this is a timing issue, but don’t know enough to resolve the problem.

This question I posted to the usenet group alt.comp.periphs.videocards.nvidia and to the Media Portal Hardware Support forum: http://nolanparty.com/mediapo rtal.sourceforge.net/phpBB2/viewtopic.php?p=33148#33148

The Media Portal posting resulted in a number of suggestions from a friendly chap, leading to a pointer to information about digital video resolution and aspect ratio conversion.

Links

The TweakGuides site offers a useful article.

Here’s a forum in which the same question has arisen: http://www.thegreenbutt on.com/community/shwmessage.aspx?ForumID=47&MessageID=94536&TopicPage=1

A couple of sites that provide forums worth inspecting every now and again:

If you’re interested in understanding some of the technical details about WSS then Steven Hosgood’s PALPlus page is a good place to start.

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