Black Rock's Jefferies talks LCD screen resolutions
Here at Black Rock we use 26-inch widescreen Sony Bravia LCD TVs. We chose these devices because they gave good image quality and were very popular; the theory being that we should develop games on hardware as similar as possible to that which our customers use.
This LCD model advertises its display format as 720p, but on closer inspection it’s not 1280x720 like you’d expect. In actual fact, it’s got a pixel resolution of 1366x768. Of course, LCD TVs can only display images at their native pixel resolution; if they try and display any other resolution then they need to first scale that image or letterbox it. The Bravias we use don’t have the option to display letterbox through HDMI-A and, in any case, even if they did it’s doubtful the consumer would know about it.
So, in order to display the 1280x720 output image from our game, the LCD must first use its hardware scaler to scale the image by 106.66 per cent in both axes. The lovingly crafted 1280x720 image has gone to be replaced by something dependent on the quality of the LCD scaler. But no matter how competent the scaler is, it’s difficult to image how scaling by 106.66% could do any good to the image.
So what is it about 1366x768? There are millions of these LCDs out there but the resolution doesn’t look familiar. It’s not a power-of-two, it’s not divisible by 640 and it’s not even an exact 16:9 aspect ratio (although it is pretty close).
NEW YEAR’S RESOLUTION
The best I’ve managed to come up with is that it’s the highest resolution at nearly 16:9 that will fit into a megabyte boundary.
Multiply 1366 and 768 together and you get very nearly 1024x1024, or 1 megabyte. This means that the LCD manufacturers can use off-the-shelf video memory with very little wastage. On the other hand, if they were to use true 720p then they’d waste 13 per cent of the video memory and possibly lose sales to their rivals who could claim slightly higher resolutions.
So you can’t trust your customer’s display devices. That’s not exactly news – that’s been the case for as long as consoles have existed – but what’s interesting is that this time the problem is being exasperated by our desire to hit 720p.
The first thing to note is that we all make trade-offs between image resolution and quality. Probably the most noticeable example of this is multi-sample anti-aliasing. Both hi-def consoles support either 4xMSAA, where the scene is anti-aliased vertically and horizontally, or 2xMSAA, where the scene is only anti-aliased vertically or horizontally. However, if you’re throwing a lot of graphics around then you won’t be able to afford 4XMSAA at 1280x720 because the GPU hit is just too great.
At this point most games, including our games here at Black Rock, drop down to 2xMSAA at 1280x720. We are making a trade-off and saying that the screen resolution is more important to us than the quality of the anti-aliasing. This isn’t necessarily an entirely voluntary move because, until recently, Microsoft had a TCR insisting that games run at 1280x720 – providing you weren’t one of the lucky ones like Halo, who got it waived and ran at 1152x640, that is.
By asserting that screen resolution is more important than anti-aliasing we’re leaving ourselves vulnerable when the customer’s LCD decides it’s going to rescale the image to a new resolution anyway. If we instead assume that the LCD is going to rescale then, for some games, it might be more sensible to present it with a better anti-aliased but lower resolution image in the first place.
As more and more LCDs ship with the full HD resolution of 1920x1080 then this will become less of an issue, but I’ve just had a look on Amazon and all the 26" and 32" Sony and Samsung TVs are still 1366x768.
It’s is for this reason that Microsoft recently retired the TCR insisting on 1280x720. Now we are free to make the trade-off between resolution and image quality as we see fit.
David Jefferies started in the industry at Psygnosis in Liverpool in 1995, eventually working on Global Domination and WipEout 3. He later moved to Rare where he worked on the Perfect Dark and Donkey Kong franchises. Next came a move down to Brighton to join Black Rock Studio (which was then known as Climax Racing) in 2003. On this generation of consoles he’s been the technical director of MotoGP’06 and MotoGP’07 before starting work on new racer Split/Second.