Picture loss with DVDMax has nothing to do with TV overscan

[paaltio]

Like many others here, I've been wondering why there's much more picture visible when watching a DVD on my monitor than on TV where the picture is sent through the G400's TV output using DVDMax. The usual explanation seems to be that this happens because TVs have overscan. However, the amount of picture lost is so big (almost 10% in my case) that this doesn't sound correct. But as there was no way to confirm this, it was kind of hard to prove it either way.

However, recently I bought a new 16:9 TV to replace my age-old, cheap 4:3 TV and was amazed to find out that the amount of this alleged overscan was EXACTLY the same. Using DVDMax, there was a considerable amount of picture missing from all sides of the picture (left, right, top, bottom -- you just can't see the top and bottom missing so much, since most DVD titles are in letterbox). These two TVs are made by a different manufacturer and the other one is more than five years old. This makes for an interesting coincidence if one still claims this happens because of overscan, doesn't it?

The widescreen TV has a 4:3 mode where black bars remain on the left and right sides of the TV screen so the original aspect ratio of normal TV picture is preserved. As overscan by definition means picture being cropped due to it going "out of boundaries" of the TV, there can't be any overscan in this 4:3 mode on the left and right sides, won't you agree? And guess what, there's EXACTLY the same amount of picture missing when I'm watching the picture outputted by DVDMax in the 4:3 mode.

Today, when a local TV channel here was sending the "test picture" (you know, the one where they have all sorts of geometric figures and colors so you can see whether your set is showing the picture correctly), I tried to make sure there was no overscan involved. And sure enough, in the 4:3 mode, even the outermost squares in the picture were fully visible. When I switched to the 16:9 mode where the whole screen is filled, the squares were cropped slightly, almost not noticeably; at most 2% or so. So at the same time this serves as proof that in the 4:3 mode there is no overscan on the left and right sides and that the amount of picture lost due to overscan in a new TV set is minimal.

The question is, what/who to blame then? The amount of picture lost is the same no matter what G400 driver version or what DVD player software I use. It definitely looks like it's Matrox's fault. While I doubt they're going to do anything about this, I sincerely hope they will, because I really can't stand looking at a movie with someone's face only shown half because of whatever reason. If there isn't going to be a fix (and I'm not mistaken here suspecting Matrox screwed up), I guess I'll have to throw the G400 to the wall and buy something that works.

Don't get me wrong, I've really liked Matrox's products in the past and thoroughly enjoy the G400 and can live with its small problems otherwise, but this is just too much for a DVD hobbyist like me. I've been ripping my hair off for months because of this. The only solution has been to tell Cinemaster (or PowerDVD, or WinDVD etc.) to ignore the original aspect ratio and shrink the picture a bit horizontally. However, this introduces downscaling artifacts that are even MORE annoying that the loss of picture, so it isn't viable.

[CrazyBee]

Have you used a stand alone DVD player to verify what you have observed?

The reason I ask is that I have seen equal if not greater amounts of cropping on a DxR2/3 on a TV.

Also, how do you know that the TV station is not compensating for the overscan?

I personally believe it IS the TV and not the the G400 or DxR2 or DxR3 since I have seen DVDs on all three of these devices outputted to either a TV or directly on a monitor and have noticed the overscan.

I have seen DVDs on a standalone unit but I don't remember at teh moment how much was lost due to overscan.

Also, the image is also cropped by filtering of the incoming signal via the TV's input circuitry. Its basically video noise filtering. Kinda how Dolby B,C, or S, will loose some of the audio (low and high end portions) to strengthen the remaining.

[paaltio]

Well, you might have a point there. I was wondering whether TVs do that, ie. crop the sides even before the picture is shown. Is there some kind of standard concerning that then, considering these two TVs that have an age difference of over five years filter exactly the same amount of picture?

And I'd still want to note the test picture example. Horizontally, the picture was shown in its entirety in the 4:3 mode on the widescreen set. So why would this TV *not* filter a normal picture (which is more likely to have all kinds of noise anyway) but still do that to something that comes through a compose/s-video/scart connector?

[Pertti]

paaltio,

So far, I have seen just one TV-set, which was actually showing Full Screen, and it was even mentioned on the stickers and the prochures.

All the other TV:s have hidden part of the picture. But, on the other hand, when I am looking at live feed from a TV station, I can see more with the Matrox cards, irrespective of where the signal is coming in from (built-in tuner, Composite, S-video)

[paaltio]

Well, whatever the real reason behind the lost picture, an easy solution (even if a little clumsy) would be if the DVD Player companies (Ravisent, Cyberlink, Intervideo, whoever) implemented an option to their programs that would add black space to the sides. Because in case this problem has nothing to do with the G400 itself and is universal, I would imagine such an option would have lots of potential users. It would also be very easy to do programming-wise, so I don't quite understand why it hasn't been done already then...

[cjyo~]

Yes, this is overscan.

I'm not sure if there is an official exact ratio, but basically the story (that I heard) is that your TV picture (on the tube) shrinks over time, so the extra room on the edges is to compensate for that.

I've been working in DVD production for 4 years and all movies have more picture than you normally see. On a professional $5,000+ NTSC monitor you can actually see much more on the edges, and there is a button so you can see the whole picture, including Line 21 (closed caption) and macrovision signals.

If you want to know how much you are missing, you can measure the aspect ratio of a letterboxed movie, which should usually be 2:35 to 1 or 1:85 to 1.

I did this on my home TV on the Airforce One laser disc and the aspect ratio I got was about 2:17 to 1.

[paaltio]

Then am I mistaken in how overscan is defined? Like I said earlier, I've always thought of it as nothing more than the picture on a TV being a little larger than the actual screen area so that all the sides are cropped slightly. That is, the sides get cut only when they don't "fit" to the screen.

In this case, the picture definitely gets cropped *before* it's shown on the TV tube. Does overscan include this also, then? In that case, the whole word "overscan" is a little misleading, since it definitely seems to suggest the picture going _over_ the boundaries of the screen etc.

[dZeus]

A very easy way to check if the picture loss is due to overscan is to connect the TV-out of the G400 to a device that converts the TV picture to VGA (TV card or something). All the devices which do this I have checked do not generate overscan, so you can easily check if the tv-out is outputting the complete picture of leaves parts out of it.