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Old 11-21-07, 01:47 PM   #1
SMorgan
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Default Could Nvidia Comment? Widescreen Aspect TV-Out Resolutions

First I feel I should apologise for asking this question here, since it really doesn't seem to be the right forum for this question. However all my attempts to contact Nvidia have been rebuffed and they send me here instead.

I'm looking for a response from an Nvidia employee and my ultimate goal is to see the driver changed in future. My question is this: Why does the internal list of acceptable TV-Out resolutions not include 1024x576 (16:9 PAL) and other widescreen aspect ratios? I can understand limiting the list to valid resolutions but why are widescreen aspects not on that list?

Searching this forum and the internet in general shows that this is frequently asked question however there doesn't seem to have been an official response. It's a particularly frustrating issue for users and developers of various media centre solutions where we are wanting to output widescreen SD material to widescreen TVs. It's not just the video but the UI scaling which is affected. Interestingly this doesn't seem to be an issue limited to linux, Windows users are complaining of the same thing when trying to get Windows MCE to understand that although the resolution is 4:3 or 5:4, the display aspect is 16:9.

I pretty much feel like I'm wasting my time asking for this to change, but who knows? There are always alternatives, such as downgrading drivers to versions which didn't have these restrictions or using Intel/Ati chipsets instead. Our current advice to users is to pick an Nvidia card for their media centres, but with better drivers on the way from ATi that might change.

SMorgan - MythTV Developer
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Old 11-21-07, 02:22 PM   #2
Thunderbird
 
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Default Re: Could Nvidia Comment? Widescreen Aspect TV-Out Resolutions

It is a general misconception that widescreen is a higher resolution. In fact in case of widescreen there are 'black' borders introduced in the signal. Due to that you in fact lose information. (So you have 720x405 or so assuming the default is 720x576 which is what nvidia's tvout renders at in all cases)

'Real' widescreen DVDs are sent out in 'anamorphic' which means that the image gets compressed in the horizontal direction to fill the whole 720x576. The tvout stretches the image out and this way you use the full 'resolution'. (so the width of a pixel is smaller than the height)

If you would render a horizontally compressed image and you set the widescreen flag in the tvout signal (which videocards don't set) you would use the whole set of data. The problem is that in a PC all pixels are squares....

Older nvidia drivers allowed you to create custom modelines but really those didn't do much, the tvout chip ALWAYS renders at 720x480 or 720x576 and if you select 1024x768 the image is scaled to the tvout resolution.
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Old 11-22-07, 02:29 AM   #3
pe1chl
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Default Re: Could Nvidia Comment? Widescreen Aspect TV-Out Resolutions

The correct behaviour would be to offer a virtual resolution with a widescreen aspect ratio, then scale that resolution to 720x576 in the video encoder (just like it scales computer-typical resolutions) and indicate in the output that the picture is widescreen. Then you would produce the correct anamorphic widescreen signal.

Second-best would be to have a 720x576 resolution and have an option to send the widescreen signal. The scaling would then have to be done by the videoplayer software.

But of course the nvidia tv-out is too limited to do either of that.
It is still my opinion that you should avoid this tv-out like the plague when you want anything resembling quality. It is much better to use a TV with computer input and connect VGA, DVI or HDMI to that. Then you bypass the tv-out chip with all its silly limitations and useless functionality.
(after all, who wants to encode their TV signal in PAL or NTSC when it is possible to use RGB or YPbPr without this encoding loss. it is better to buy a new tv than to spend money on a limited tv-out "solution")
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Old 11-22-07, 03:08 AM   #4
Thunderbird
 
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Default Re: Could Nvidia Comment? Widescreen Aspect TV-Out Resolutions

Most people don't have HDTVs, that's the problem. I think the nvidia hardware is at least capable of 16:9 scaling and perhaps somehow the widescreen flag can also be set in the signal but nvidia isn't doing it. We might be able to do it in nouveau. If you want to have tvout in the opensource nouveau driver check http://nouveau.freedesktop.org/wiki/TestersWanted.
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Old 11-22-07, 03:33 AM   #5
pe1chl
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Default Re: Could Nvidia Comment? Widescreen Aspect TV-Out Resolutions

Quote:
Originally Posted by Thunderbird
Most people don't have HDTVs, that's the problem.
That is a diminishing problem. What is sold in the stores today usually is at least "hd ready".
The people who want to watch movies in widescreen are more likely to have bought an LCD or Plasma already, and the generation of TVs with widescreen CRT does not have a very long lifespan anyway (both due to generally low build quality and production defects in some CRTs).

When there is a solution that works well with VGA, DVI or HDMI (also not a troublefree area in the nvidia driver...), it will serve a majority of interested people in the coming years. Those that keep their TV for 15 years probably are not very interested in quality aspects and are usually not the first-in-line to build a media centre...
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Old 11-22-07, 02:45 PM   #6
lpowles
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Default Re: Could Nvidia Comment? Widescreen Aspect TV-Out Resolutions

Quote:
Originally Posted by pe1chl
The correct behaviour would be to offer a virtual resolution with a widescreen aspect ratio, then scale that resolution to 720x576 in the video encoder ...
I think is the best and only solution that should be considered. That way you dont have to worry about applications that dont support scaling (eg. photo galleries which distort photos at the moment, etc).

Quote:
Originally Posted by pe1chl
... Then you bypass the tv-out chip with all its silly limitations and useless functionality.
I agree. Although I'm a bit disgruntled at having bought a GPU advertised with HDTV output .. only to find out it doesnt support 50Hz and nvidia has ignored posts for at least the last 3 years from customers asking this question. So I agree, I think it would be better for the tv encoder to be dropped completely than to have a dodgy attempt with partial support in there.

On the other-hand I would love for my 50Hz HD-CRT to work. I think there is still a bit of market for this as I know several people who prefer the picture quality of CRTs .. so I was going to investigate finding a tv encoder datasheet, etc. and try and engineer it myself, but i havent had time for the past year so i'll be looking at nouveau now .. thanks for pointing to this project!
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