s-video tv-out resolution question (1 Viewer)

[Matt Weyen]

I borrowed a friends computer to test a ATI Radeon 8500 (oldest version made) on my tv (Sanyo 32" ntsc). I got the resolution at 640x480 to play a movie without losing anything or stretching the video in any way immediately, but with some effort I got it to do 800x600 with no loss (by squishing the image in both vertically and horizontally). 800x600 looked amazingly better than 640x480 (didn't squish/stretch the video in any strange aspect ratio either). and so naturally I tried 1024x768 but didn't even get close to squishing it all into the screen. Does anyone know a video card (preferrably cheaper than $80) that is capable of squishing 1024x768 into an NTSC 32" screen? Otherwise, I'm going to buy myself a ATI Radeon 7200 ($42) and have 800x600, which looked very good (very close to my stand alone dvd players quality) and play all the media I store on my pc (LOTS!).
Other people's experiences would be great to hear. Thanx.

 

[Jeff Kleist]

You don't want to do 1024x768 on a standard TV

NTSC resolution is 720x480, so 800x600 is your best choice

 

[Vince Maskeeper]

I'm confused on exactly what you're trying to do and what you're comparing the results to- but as Jeff said above-- 1024x768 is not a TV resolution- and so most cards don't even both to try to downsample it for TV output. The best is 800x600 (and even that is downconverted to 640x480 interlaced for TV output).

-V

 

[Matt Weyen]

I was just interested in finding a tv-out card that might do a better job than the Radeon for a comparable price. I am building up a htpc to play divx movies and other random downloaded media from my pc that is too far away to connect currently (downstairs,upstairs, rented house issue). Since I have a lot of left over parts from other upgrades and the thought that someday I might get an hdtv (probably 2 or more yrs away) is kind of enticing me to build it while I can. I just realized that I have no need for a monitor other than the initial hookup so I decided that building it would be feasible, $wise.

 

[JoshR]

This has been confusing me for years:
Which is it? If it's both, what don't I understand?

 

[Jeff Kleist]

It IS both

But the computer doesn't want you losing edges with overscan, so it renders to 640x480 and sticks that in the middle of the 720x480 area

 

[DeepakJR]

divx huh?......sounds interesting...
l8rz,
Deepak Jr.

 

[John Parris]

Matt-- I think you're going to find that the quality of all video cards S-video output is really weak at best... the Radeons I have seen (including my own Radeon VE) have it pretty bad compared to a couple of other cards Ive seen used... I'd say it doesnt make that much of a difference if you're using it sparingly and to just get something that... well, WORKS. Radeon would do it... but no need for the high-processing and frills of the 8500... there's lesser cards that would get the same thing accomplished

 

[Vince Maskeeper]

As jeff said- it kinda both.

The problem is that TV pixels are not square, computer pixels are. So, technically speaking- if you're preparing video on a PC for output to DVD or VHS- the resolution you should be working with is 720x480.

However- this won't really show you what you will see on the PC screen, because the computer with its square pixels shows 720x480 as 1.5:1 aspect (quite obviously wider than TVs 1.33:1). Images from TV to the PC screen will look skewed slightly if viewed natively- so often the computer will have a mode which displays the TV image with different pixel shape- making the 720x480 image fit in a 640x480 area on the screen- giving the proper aspect and eliminating the picture distortion.

This creates an interesting problem when creating titles, as you have to create them at 640x480 and then stretch them out to 720x480 before adding them to your project or they will be skewed in the TV screen...

So, when playing computer games- usually the 640x480 computer image is processed into a 720x480 interlaced image by the card. Again- with the difference in pixel shapes, the same image will appear to look the same despite different core resolutions.

Hope that makes sense.

-Vince

 

[JoshR]

Let me see if I got that. The NTSC standard, as viewed on TV sets since it's invention, is 720x480(and I have a question about that, coming up ). But those pixels are tall, so if you transfer them to a computer screen, they'll be stretched width-wise to become square pixels. For it to look right, it has to be squished back width-wise, so 720 becomes 640 on a computer screen. Conversely, anything going from your computer to your TV has to be stretched to 720 first, or it'll look tall on the TV.
I think I understand!
The only thing left is: If NTSC has 525 horizontal scan lines, shouldn't there 525 lines of vertical resolution? Why isn't it 720x525?

 

[Vince Maskeeper]

Not all 525 lines are used for picture data. The top level lines of availble carrier are used for other types of data: closed captioning, macrovision, that sort of stuff.

Does that help?

Vince

 

[JoshR]

That helped very much. Thanks!