Show Me The Pixels! The Importance of PPI

[Jason Dunn]

I was thinking about the issue of enhancing the Pocket PCs resolution again, especially in light of the recent announcement yesterday of small PDA screens reaching 800 x 600 resolution soon. I can't find a reference to this on Google, but I remember reading that the clarity of printed text on a page is equal to around 300 ppi. That sounds about right to me - 300 dpi laser printed text looks much better than 150 dpi, but about the same as 600 dpi text, so I think that's the human sensory threshold. So let's break this down...<!><br /><br />• The Pocket PC at 320 x 240, with a 3.5" screen has a 110 ppi.<br /><br />• The Pocket PC at 320 x 240, with a 4" screen (Genio) has a 100 ppi. That 10 ppi makes a difference if you can believe it - I even noticed it when I looked at the screen. Text looked a little bit "blockier". People also comment regularly that the text on the iPAQ 1910 looks a little sharper and crisper than the text on the iPAQ 5450.<br /><br />• The newest Sony Clie at 320 x 480 with a 3.5" screen (I scoured Google and couldn't find the exact screen size, but it's got to be close to that) has double the number of pixels a Pocket PC, so the ppi value is around 164 or so. Looking at text on the Clie is nicer than looking at text on a Pocket PC.<br /><br />If we were to get the Pocket PC to 640 x 480 resolution on a 3.5" screen, we'd hit 229 ppi. :-) 300 ppi is the holy grail of LCD display crispness, and I think smaller devices will reach it before desktop monitors do. Although the screen resolution of Pocket PCs is certainly "good enough" for most things, I was really blown away by the crispness of the text on the Clie devices. Same thing with the Zire 71 - the text was very sharp and easy to read.<br /><br />The problem is that we can't just up the resolution - if we double the resolution on the Pocket PC, everything will get twice as small. That might be useful for some people, but it's not a good solution overall. What we really need is a resolution-independent operating system. One that has a relative size setting for a variety of resolutions, with font and icon settings that will grow proportionately. It's just like having a higher resolution on your desktop screen - the more pixels are using to draw each item, the crisper and cleaner it will look. But the more pixels is used to draw something, the smaller it gets - I know, it makes no sense. :| <br /><br />This issue affects every desktop computer too - Windows desperately needs the same functionality. 1600 x 1200 resolution on a 15" screen requires excellent eyesight to use, because there's no easy way to say "make everything on the screen bigger". You can adjust the DPI, but while it makes everything bigger, it also drops the quality of the displayed items.<br /><br />This whole topic makes my head hurt (hopefully I got it all right), but the bottom line is that we need 640 x 480 on our Pocket PCs, and an operating system that will support it in a slick fashion. Microsoft, we're waiting. :way to go:

[msprague]

If my calcs are close the display on my digital camera is 330ppi. Of course it is TFT, not transflective.

[nobody]

Sharp cl model (Linux) has 640x480. PPC should not have problem getting it.

[Fitch]

This is why many people push flash-- it's already perfectly scalable and very powerful. And people have wanted a scalable GUI OS for decades, yet, sprite-based OSes have still pushed forward. I guess 'cause they're just way less processor intensive (floating point vs. integer calculation)

I think your estimates that 300dpi would look incredibly slick rely on proper anti-aliasing. If there's no ClearType-type of text rendering, it still won't look as good as an inkjet print (remember, a laser printer has always had perfectly rounded text edges, even at 150dpi, it's the graphics that didn't look good. Text on a laser printer is done with lasers that can do infinite-resolution curves, it's the ink jets that are the paper-equivalent to a computer display)

[kuyars]

Well, I responded to the earlier thread about the resolution deal. I brought up the Sharp Zaurus SL-Cxx line which have a 3.7 inch screen and are 640x480.

I had a SL-C700 and a Clie SJ33 and an Ipaq side by side at a store in Japan (cant remember which model of ipaq exactly though) and the 640x480 made a HUGE difference in the crispness of the fonts and icons. Everything was just significantly sharper and it's not even just a slight thing. The difference was day and night. In the order of how good the fonts/icons looks, it went from Sharp C700 to Clie SJ33 and finally to the Ipaq.

I dont know if anyone has access to the SL-Cxx series, but take a look and I'm quite sure that the difference will be immediately apparent.

[Dr. Grabow]

As you pointed out, screen size is also very important. I use my Tungsten C very little because although the PPI and resolution are good, the actual screen size is too small. Day to day, using a Pocket PC, even the Genio, is easier for me than higher-res but smaller screens ...

[Perry Reed]

I understand that Longhorn (the next version of Windows) should have a new graphics system for driving ultra-high-res screens on the desktop. That ought to be pretty nifty.

[Jason Dunn]

I think your estimates that 300dpi would look incredibly slick rely on proper anti-aliasing.

Correct. I like what I see with the Sony devices, so I know they're on the right track - text looks AWESOME on them.

If there's no ClearType-type of text rendering, it still won't look as good as an inkjet print (remember, a laser printer has always had perfectly rounded text edges, even at 150dpi, it's the graphics that didn't look good.

Are you sure? I could have sworn I used to be able to tell 150 dpi laser printing from 300 dpi laser printing - but maybe it was using TrueType fonts not on the printer, which makes them essentially graphics. I think. :|

[sponge]

I've noticed Opie (ie what Zaurus uses, along with iPaq if you flash it) seems to be pretty resolution independant, most properly coded programs can scale as needed, even to landscape. All you need to do is click the little launcher button, and hit rotate, and your in landscape mode. Can't test with any larger resolution screens, obviously.

[Janak Parekh]

Are you sure? I could have sworn I used to be able to tell 150 dpi laser printing from 300 dpi laser printing - but maybe it was using TrueType fonts not on the printer, which makes them essentially graphics. I think. :|
I've gotta ask the same question. There's no such thing as an infinite-resolution laser printer. While TrueType fonts would be sent as vectors, not rasters, to the printer, the printer would most definitely rasterize it. This is why you can see a HUGE difference between 300dpi engines and 600dpi engines. It's very noticeable close up. A 300dpi LCD could absolutely benefit from ClearType (to give the impression of even higher resolution), but it should appear amazingly sharp even without it.

--janak

[Jason Dunn]

I understand that Longhorn (the next version of Windows) should have a new graphics system for driving ultra-high-res screens on the desktop. That ought to be pretty nifty.

Yup - that's one of the things that I think will help make this happen on the PPC side of things. Microsoft is waking up to the fact that they need a resolution independent solution. When they optimized Windows XP for 800 x 600, they were going in the right direction, but they didn't quite follow through to the logical next step...

[donkthemagicllama]

It's just like having a higher resolution on your desktop screen - the more pixels are using to draw each item, the crisper and cleaner it will look. But the more pixels is used to draw something, the smaller it gets - I know, it makes no sense. :|


Err... I think you need to reconsider that statement... it makes perfect sense!

The problem on your desktop is that when you up the resolution it uses the SAME number of pixels to draw each item, but the pixels are smaller.

You're not using more pixels to draw something (an icon, say), you're using the same number of pixels, your just putting more pixels in the same area, so something that is made from a static number of pixels will be smaller.

If you draw an icon that is 64 pixels wide, and display it in 640x480, it will take up 10% of the screen width, whereas at 1280x768 it will only take up 5% of the screen width and look half as wide. You could force it to appear the same width by doubling the pixels so your icon is now 128 pixels wide. It will take up the same 10% of screen width as the 64pixel icon did at 640x480, but it won't look any better.

[JonnoB]

The NeXT system (remember Jobs in-between venture after and before Apple?) used retargetable Postscript for its display. Although the monitor had a DPI limitation, the OS did not and as a result, documents always looked as crisp as the display could view them.

Although Windows already supports relative positioning, the GUI development tools are still made on relative pixel size instead. The whole framework has to be changed before we realize these kinds of improvements.

[kamodt]

The Bsquare "Power Handheld" reference device uses the Toshiba 4", 640x480 display. It has at least 200+ dpi and looks amazing. We wanted to provide a full webpage view in a pocket-sized device but we found that the text was pretty small on most pages. One solution was to provide a "Zoom mode" which allowed you to zoom at 2X to view portions of the page as needed.

The more important issue was that we couldn't use the Pocket PC software. While WCE is capable of supporting any resolution, the Pocket PC team decided to draw the line at quarter VGA. They designed the UI of the apps so that it was optimized for this resolution and refused to consider others. Their reasoning was that QVGA displays were readily available and less expensive than other displays and preferred to focus on something that would keep costs down. It sucks for anyone wanting to expand beyond QVGA but that's the way it is.

The Power Handheld can be seen at: http://www.bsquare.com/products/powerhandheld.asp

Keith Amodt
Former MS WCE PM and Bsquare Product Planner

[rbrome]

I have to agree. One size does NOT fit all for PPC screens these days.

The hi-res trend is starting to ramp up with mobile phones. Recently I had a chance to try the Sony Ercisson SO505i - the hot new Japanese 1.3 megapixel camera phone. It has a 256x320 display, and it's amazing. The resolution at that size is amazing. Sharp's upcoming camera phones for Europe will have similar displays.

MS needs to wake up. Phone displays already have more pixels than their newly-updated OS can support. That's not how it's supposed to be.

[KayMan2k]

I understand that Longhorn (the next version of Windows) should have a new graphics system for driving ultra-high-res screens on the desktop. That ought to be pretty nifty.

Yeah, and Jason's "make everything bigger" option will be introduced. The Longhorn project dates back (publically at least) to 1996 under a name called "chrome effects". That was, to create a fully DirectX managed windowing environment - which is just now beign introduced. But it comes at a price, it will require a pretty hefty 3d accelerator - but in 2004 those should be around $50 or less.

[kaizer soze]

Forget about text, think about the difference resolution makes on graphics/gaming/etc. I think upping the resolution would spur a lot of development.

[klinux]

Yeah, and Jason's "make everything bigger" option will be introduced. The Longhorn project dates back (publically at least) to 1996 under a name called "chrome effects". That was, to create a fully DirectX managed windowing environment - which is just now beign introduced. But it comes at a price, it will require a pretty hefty 3d accelerator - but in 2004 those should be around $50 or less.

Yup, one of the reasons why Mac's good look good is that their desktop is based on OpenGL aka Quartz Extreme so everything has a rendered 3-D look.

[PJE]

How dare you start a discussion of screen resolution while I was away from my computer! :wink:

It's interesting that the 800x600 screen is made by switching the backlight between Red/Green/Blue at a high rate, thus displaying the three primary colors in a time sliced manor. It definately would require fewer LCD pixels (320x240x3=230K, 800x600x3 (old style)=1,440K, 800x600x1 (new style)=480K) but would still give the CPU/GPU a lot of work to do to draw the display...

It would also stop cleartype from working... as there is no pixel order for it to make use of. For cleartype the current LCD (assuming the RGB pixels are in the 240 direction) is 720x320 sub-pixels, therefore this new screen would not look much better for text than a well optimized cleartype screen. However graphics should look better, and it would remove colored edges to text. As an aside it would also look equally good in both portrait and landscape.... (now don't start me on that one!)

As I've stated before (too many times for most people :wink:) my next PDA will have a higher screen resolution than 240x320 (and proper landscape) as the current limiting factor for me when viewing content such as HTML pages is not text size but text clarity - the number of pixels used to produce each character.

My 2c.

[LarDude]

For cleartype the current LCD (assuming the RGB pixels are in the 240 direction) is 720x320 sub-pixels, therefore this new screen would not look much better for text than a well optimized cleartype screen.


This raises an interesting question. In current LCDs, are the pixels actually
RGB in the 240 direction? Does anyone happen to know? Or are they
"squares" of

RG
GB

(i.e. like the CCD masks/filters in some digital cameras)?

[William]

We already new Janek was a superhuman but here's the evidence:
That sounds about right to me - 300 dpi laser printed text looks much better than 150 dpi, but about the same as 600 dpi text, so I think that's the human sensory threshold.
This is why you can see a HUGE difference between 300dpi engines and 600dpi engines. :wink:

[Janak Parekh]

We already new Janek was a superhuman but here's the evidence:
Uh... ok, maybe HUGE is an exaggeration. :lol: But really, if you look closely between 300dpi text and 600dpi text, especially small text (say, 6pt), it's noticeable. (Besides, I think that's what Jason meant.)

--janak

[jage]

This raises an interesting question. In current LCDs, are the pixels actually
RGB in the 240 direction? Does anyone happen to know? Or are they
"squares" of

RG
GB

(i.e. like the CCD masks/filters in some digital cameras)?

Mostly RGB horizontally (or 240 px direction), sometimes vertically, like ipaq 38xx, in the 320 px direction.

[Kati Compton]

I think I'd be pretty happy with 640x480 on a 4" screen.

Kati

[jage]

Remember that there are 4 times more pixels to push in 640x480 mode. 320x240x16bit comes to around 150kB. 640x480 is then around 600kB. If you had 10MB/s bandwidth to display buffer, which is common on current PPCs, the highest possible full screen framerate would come to around 16, that is, the CPU just pushing pixels to display RAM. Games would suffer tremendously, in that scenario, even simple shoot 'em ups & platform games would probably max out at 10fps.

To realistically accomplish 640x480 resolution on PPCs, it would also require quite heavy graphics processor (=power consumption). It would also need at least doubling memory bandwidth to move all that extra graphics data around. Maybe something like http://www.bitboys.fi/products.htm or even http://www.arm.com/armtech.nsf/html/MBX3D?OpenDocument would do the trick. The graphics core would need to support hardware nearest neighbor, maybe bilinear as an option zoomed blitting, YUV->RGB conversion overlay or blitting, preferably combined with zoomer. Then of course some basic line drawing and filled rectangle for UI acceleration, the rest would be pretty unimportant (like who needs filled ellipses and such).

New graphics APIs would be required to use the graphics chips, preferably OpenGL, although knowing Microsoft they'd likely put something downscaled proprietary DirectX stuff in. GX.dll (something that many games use to access graphics frame buffer directly on current generation of PPCs) would probably need to emulate 240x320 by default, by setting up pixel doubling or risk losing compatibility.

It'd also possible to create a such compatibility mode in GWE (PPC equivelant for GDI) that bitmaps and coordinates would be doubled and things like text rendered in higher resolution for legacy applications.

Anyways, be careful what you wish for, you might even get it... The price you might need to pay is incompatibility, power consumption and performance, although I do agree 480x640 resolution would be more than welcome for previously stated reasons.

[Scott R]

I think that there are several things at play here. First, I don't see why this necessarily has to be such a huge undertaking. I'd suggest that MS copy Palm's approach here. If an app is coded according to standards, a device with a higher-res screen will simply upconvert it to a 480x640 "pixel-doubled" format, offering smoother fonts (and little else). Apps that want to take advantage of the full 480x640 resolution will need to be specially coded to take advantage of it.

I've seen the high-res Palm OS devices, and they do look nice, though most apps don't use the higher res for showing more data, just for smoother fonts (as explained above). IMO, the cleartype mode of PPCs do a pretty good job in that regard.

I will say that as a wireless proponent, what I'd really like to see is an 800x600 devices simply because most web sites are designed around this size. Anything less (yes, even 640x480) will require either scrolling or mangling up the site design in order to make it fit. Of course, getting the PDA hardware up to snuff to show 800x600 is only part of the battle. Current cellular wireless technology is still too slow to do an acceptable job of rendering pages. Then there's the issue of whether you can display a readable 800x600 page in a 4" screen (let alone a 3.5" screen). Sure, 800x600 will do a great job making larger fonts look laser-quality-smooth, but rendering an 800x600 web site will require displaying the fonts ultra-tiny.

Scott

[Janak Parekh]

If you had 10MB/s bandwidth to display buffer, which is common on current PPCs, the highest possible full screen framerate would come to around 16, that is, the CPU just pushing pixels to display RAM. Games would suffer tremendously, in that scenario, even simple shoot 'em ups & platform games would probably max out at 10fps.
Support pixel doubling, as Scott suggests, to prevent moving as many pixels for large games (unless you're talking GPU => LCD bandwidth, in which case this probably is moot, unless one could integrate clever circuitry into the LCD itself).

To realistically accomplish 640x480 resolution on PPCs, it would also require quite heavy graphics processor (=power consumption).
Agreed, it would require more, but it's not that bad. Witness Sony's 480x320 or even Samsung's NEXiO which does have an 800x600 display in a package not that much larger than a Pocket PC. Technology is moving real fast. :)

--janak

[Janak Parekh]

Then there's the issue of whether you can display a readable 800x600 page in a 4" screen (let alone a 3.5" screen). Sure, 800x600 will do a great job making larger fonts look laser-quality-smooth, but rendering an 800x600 web site will require displaying the fonts ultra-tiny.
Again, anyone who uses Thunderhawk would agree with me -- I don't think it'll be as much of a problem as we might visualize. You definitely want the option to have the core fonts larger, but I'll take that 800x600, 4" screen any day for webbrowsing.

--janak

[ctmagnus]

I'll take that 800x600, 4" screen any day for webbrowsing.

--janak

Until some weiner posts a 1600x1200 screenshot of his gf's desktop, that is. ;)

[Timothy Rapson]

Jason, you math is off considerably.

The screen on a Genio with 4 inches diagonal is assumbly 2 6/16s or so
The screen on an Ipaq is 2 5/16 inches wide.
That on my Clie and virtually all 3.5 inch diagonal PPCs is 2 3/16.
The smallest common PDA screens are 2 1/8 inches wide.


One can tell the difference between those models if you look real close, but the practical difference are negligible. That is, you can tell the difference if you look hard at two models held right next to each other, but you could not hold one at arms length to the left and then look at another at arms length to the right (not seeing both at the same time) and tell much difference in display size. The differences are less than 16%.

The resolution/ppi/pixel density (whatever you call it, PPI is a new one on me, but sounds fine) is far different on a common Palm OS, PPC, and high res devices like my Clie. The differences in a full VGA display (as on the latest Zaurus clamshell) are another huge step up.

If we disregard the 16% difference in screen widths and suppose for the sake of simplicity that each screen is 2 inches wide (a small assumption, but you are free to disregard this whole post if you want to argue about it.) you get these PPI:

Basic Palm 80 ppi (unacceptable for me, so I never got a standard Palm)
PPC 120 ppi
Clies 160 ppi
VGA Zaurus 240 ppi


That VGA is approching the 300 dpi that I also find a real threshold of perception. I strongly disagree that there is a significant difference between 300 and 600 dpi lasers. One can tell the difference, and most laser do print now at 600 dpi, but it is mostly because it is so easy to do, that manufacturers don't want to lose a sale for the $2 per printer that it may cost. In fact, my 160 dpi Clie is so good that I really cannot see the differnce between cleartype (actually, WordSmiths version called Finetype) and non-cleartype so Microsoft could just drop Cleartype altogether for new higher resolutions. This should actually help boost speed as well, as cleartype must reguire some CPU horsepower to render three sub pixels for each standard pixel.

The mystery to me is that my desktop screen is 800 pixels wide, but because the typefaces are so carefully rendered, one would hardly notice that at 10 inches wide it is exactly the same 80 ppi of that standard Palm. I can only assume that the nature of the CRT vs that of an LCD (anyone who has both and LCD and CRT of the same size and resolution want to help me out and comment about which seem more stairsteppy?) I believe Windows on the desktop includes a kind of anti-aliasing for CRTs to make them look better than LCDs at the same ppi.

And Microsoft had all the scalability you could want in the first release of Windows CE. I think their setting QVGA as the standard was an exceptionally good choice. Things look better at higher ppi, but at the sizes of the screens and the distance they are typically held from the user's eye they are an optimal balance of looks vs function vs costs. But, that was what....5 years ago? 2003 was the year MS reallyshould have gotten out that old code and encouraged VGA screens at the high end. If Zaurus can sell a VGA PDA for $600, HP could too. And they would be selling well. But, that is up to MS & their OEMs.

Anyway, Merlin (is that the next PPC version code name?) will almost certainly bring VGA.

[jage]

If you had 10MB/s bandwidth to display buffer, which is common on current PPCs, the highest possible full screen framerate would come to around 16, that is, the CPU just pushing pixels to display RAM. Games would suffer tremendously, in that scenario, even simple shoot 'em ups & platform games would probably max out at 10fps.
Support pixel doubling, as Scott suggests, to prevent moving as many pixels for large games (unless you're talking GPU => LCD bandwidth, in which case this probably is moot, unless one could integrate clever circuitry into the LCD itself).


The LCD bandwidth is considerable, but yes, probably moot point. If the refresh is at 60Hz, the refresh takes 36MB/s. Not a small number on mobile devices...
Speaking about pixel doubling... but that's exactly what I suggested first? It's just not that simple you might think. Well, to quote myself, New graphics APIs would be required to use the graphics chips, preferably OpenGL, although knowing Microsoft they'd likely put something downscaled proprietary DirectX stuff in. GX.dll (something that many games use to access graphics frame buffer directly on current generation of PPCs) would probably need to emulate 240x320 by default, by setting up pixel doubling or risk losing compatibility.

It'd also possible to create a such compatibility mode in GWE (PPC equivelant for GDI) that bitmaps and coordinates would be doubled and things like text rendered in higher resolution for legacy applications.
Remember also that going from 160x160 -> 320x320 is a lot less pixels than 320x240 -> 640x480, to be exact, 3 times more. That matters a lot if there's no hardware acceleration of some sort.

To realistically accomplish 640x480 resolution on PPCs, it would also require quite heavy graphics processor (=power consumption).
Agreed, it would require more, but it's not that bad. Witness Sony's 480x320 or even Samsung's NEXiO which does have an 800x600 display in a package not that much larger than a Pocket PC. Technology is moving real fast. :)

--janak

Somehow I almost bet those two devices you mentioned are using some sort of graphics acceleration, no?

Please read my post first. ;)

[Janak Parekh]

I strongly disagree that there is a significant difference between 300 and 600 dpi lasers. One can tell the difference, and most laser do print now at 600 dpi, but it is mostly because it is so easy to do, that manufacturers don't want to lose a sale for the $2 per printer that it may cost.
Sorry! I didn't mean to imply it was a significant, deal-killer-style difference. I was just repudiating the idea that laser printers are infinite resolution.

By all means, a 300dpi desktop is near visual perception limits for typical applications. Even the most dense desktop display I know of, the Viewsonic VP2290b (http://www.viewsonic.com/products/lcd_vp2290b.htm), is 204 dpi. I've seen it at PC Expo the last 2 years -- it's based on an IBM technology, and the display is absolutely eye-popping.

--janak

[Janak Parekh]

The LCD bandwidth is considerable, but yes, probably moot point. If the refresh is at 60Hz, the refresh takes 36MB/s. Not a small number on mobile devices...
Whoa. Why are you assuming 60Hz on an LCD?

Speaking about pixel doubling... but that's exactly what I suggested first?
:oops: OK, I missed that point.

Somehow I almost bet those two devices you mentioned are using some sort of graphics acceleration, no?
My point is, they're handhelds that work and have decent battery life, from all the reports I read. The Sharp Zaurus should be added to that list.

Please read my post first. ;)
I apologize for the second comment, but I did read it....

--janak

[PJE]

Just a few of points:

1. On the laser printer issue. For almost as long as I can remember almost all laser printers have been able to vary the size of the dot and it's placement within the base resolution (300/600/1200dpi) so for text there is relatively little difference on most paper types. Graphics is another issue.

2. The 4" display is noticably bigger 'in the hand'. I think a 4" display size with 640x480 or 800x600 would be the ideal size for a power PDA. I would take 640x480 at 3.5" but even I would struggle with 800x600 on such as screen size if the same number of pixels per character were used as today and not used to make the fonts smoother.

3. While I'm at it I have a dislike for the SIP panels poping up over the display and wasting screen space. I'd like a way (like caligrapher/transcriber or graffiti2) to enter text anywhere on the screen without needing a pop-up keyboard. The OS should trap presses/slides starting over OS screen elements such as scroll bars...

[jage]

The LCD bandwidth is considerable, but yes, probably moot point. If the refresh is at 60Hz, the refresh takes 36MB/s. Not a small number on mobile devices...
Whoa. Why are you assuming 60Hz on an LCD?


Mostly because as far as I know, that's the refresh rate they're using QVGA LCDs. :) I could be wrong, do you know any better?

[Janak Parekh]

Mostly because as far as I know, that's the refresh rate they're using QVGA LCDs. :) I could be wrong, do you know any better?
Admittedly, nope. ;) I don't see why they're forced to use 60Hz, though.

--janak

[DuaneAA]

Perhaps someone could explain it in simple terms for an old non-techie type like me. About 100 internet years ago (okay, circa 1990-1991) I had a 25 mhz 386 pc. It seemed to do VGA just fine. So why is it so difficult for a 400 mhz PocketPC to do VGA?

Thanks,
Duane

[Janak Parekh]

Perhaps someone could explain it in simple terms for an old non-techie type like me. About 100 internet years ago (okay, circa 1990-1991) I had a 25 mhz 386 pc. It seemed to do VGA just fine. So why is it so difficult for a 400 mhz PocketPC to do VGA?
It's not a matter of ability per se, but rather a matter of doing it compactly, power-efficiently, and being backwards-compatible. It's going to happen, IMHO; it already exists in other platforms; it's only a matter of time before we get it, too. :)

--janak

[Jason Dunn]

Remember that there are 4 times more pixels to push in 640x480 mode. 320x240x16bit comes to around 150kB. 640x480 is then around 600kB. If you had 10MB/s bandwidth to display buffer, which is common on current PPCs, the highest possible full screen framerate would come to around 16, that is, the CPU just pushing pixels to display RAM. Games would suffer tremendously, in that scenario, even simple shoot 'em ups & platform games would probably max out at 10fps.

That's why I doubt we'd see games running at 640 x 480 without 3D acceleration - I wouldn't care so much about 640 x 480 for games as much as I want it for everyday tasks.

You're right though, it's not simply of matter of changing the OS and stepping away - we'd need the hardware to step up as well.

[Jason Dunn]

Jason, you math is off considerably.

Is it now? I based my calculations off this PPI tool (http://www.thirdculture.com/joel/shumi/computer/hardware/ppicalc.html), and I have no reason to doubt it's accuracy. If you can explain to me why this tool is wrong, please do.

Pocket PC with 3.5" screen: 114 ppi
Pocket PC with 3.8" screen: 105 ppi
Pocket PC with 4" screen: 100 ppi

Those number make sense to me - your numbers do not.

And the next OS is not called Merlin - that's what Pocket PC 2002 was called. :wink:

[beq]

Mostly because as far as I know, that's the refresh rate they're using QVGA LCDs. :) I could be wrong, do you know any better?
Admittedly, nope. ;) I don't see why they're forced to use 60Hz, though.
The ThinkPad laptop's 14" SXGA+ LCD apparently uses 50Hz instead of the usual 60Hz for some reason...

Anyways I think the holy grail paper Jason was looking for might've been some IBM research white paper?

[jage]

Perhaps someone could explain it in simple terms for an old non-techie type like me. About 100 internet years ago (okay, circa 1990-1991) I had a 25 mhz 386 pc. It seemed to do VGA just fine. So why is it so difficult for a 400 mhz PocketPC to do VGA?

Thanks,
Duane

Well, that time 16-color (4-bit) and 256 color (8-bit) graphics was prevalent. Pocket PC is using 65536 color (16-bit), that's 2-4 times more data. Also keep in mind those ancient machines started to rely on hardware graphics acceleration around that time. People accepted the slow refresh times in the applications - full screen graphical scrolling was really really slow. I remember gfx adapters could transfer around 2-5MB/s across ISA-bus and 2-3 times more across VLB, not much different to what PPCs do now (8-20MB/s)!

[PJE]

50/60Hz is a red herring.

The LCD controller handles refreshing the LCD as required. The issue is the amount of bus congestion this causes as retrieving the data to put on the display blocks the CPU from accessing memory if the data is in the main CPU memory. Some of the off-chip graphic accelerators have built in frame buffers which removes much of this congestion.

The main speed issue is with the display buffer size. Increasing the screen resolution is a very large impact on the display buffer size which makes the CPU work much harder if it has to draw all the screen contents. I only really see 640x480 or 800x600 being workable if there is significant help from a graphic controller chip to draw the basic graphic elements.

Games that want to manipulate the buffer directly will also be working harder unless there is some hardware help. Hopefully Microsoft/Chip vendors will be able to add DirectX type support to remove the need to write new code for each hardware platform.

[beq]

Some choice facts you might not know about your new iPAQ's screen (ref: http://www.pocketpcthoughts.com/forums/viewtopic.php?t=15079&highlight=#137679 ).

Re 1940:
"Its 3.5-inch transflective display is significantly larger than the h1910's 2.5-inch screen, which is helpful when viewing data but even more appreciated when viewing digital images."

Re 5150:
"It boasts a large (relatively speaking) 3.8-inch display—helpful when you need to read a lot of data."
;)

[Deslock]

I believe Windows on the desktop includes a kind of anti-aliasing for CRTs to make them look better than LCDs at the same ppi.

Nah. What you're seeing is simply from the fact that CRTs aren't as crisp as LCDs. The fuzziness (relative to LCDs) makes is look somewhat anti-aliased.

Jason, you math is off considerably.

Is it now? I based my calculations off this PPI tool (http://www.thirdculture.com/joel/shumi/computer/hardware/ppicalc.html), and I have no reason to doubt it's accuracy. If you can explain to me why this tool is wrong, please do.

Pocket PC with 3.5" screen: 114 ppi
Pocket PC with 3.8" screen: 105 ppi
Pocket PC with 4" screen: 100 ppi

Those number make sense to me - your numbers do not.

No need to take such a defensive posture... however, your math is off. The Clies are not 220 DPI (they're around 150-165). Perhaps you assumed that because the Clie has double the resolution of the PPC, it has double the DPI? (It doesn't work that way... double resolution at same size = double Dot Per Square Inch, not double DPI).

That calculator is kind of cool, but seems to be overkill... if you simply take the pixels and and divide by the length of an edge (like Timothy did), you get DPI (on any device with square pixels, which is all PDAs I know of). The discrepencies between his numbers and those from that DPI calc are so minor that they're probably from rounding differences.

This Fujitsu technology looks really interesting. If I understand correctly, instead of having individual pixels for R, B, and G, they have one pixel that can display all 3 colors. Not as cool as e-ink, but still has lots of potential. However, at three+ years out, it's hard to get too enthusiastic.

When I switched from Palm to PPC, I mentioned that one thing I missed was how crisp the images were on the Palm (PPC looks blocky by comparison). Man I got slammed for that comment here. I guess I'm not alone afterall :roll:

[beq]

FYI, same PCMag issue from above post also had a blurb about ClairVoyante Laboratories' PenTile Matrix, "which patterns pixels so that they double the effective resolution without adding cells." "PenTile Matrix works by sharing red, green, and blue cells among adjacent subpixels (see the diagram). The increased effective resolution can be used to create panels with a higher resolution while using the same number of LCD cells as a standard stripe pattern."

But I can never remember which development has been discussed here before -- they all tend to make the news round cyclically every so often...

[Jason Dunn]

The Clies are not 220 DPI (they're around 150-165).

You're right - I'm not sure where I got that number from, but the correct number is 164 ppi. I've updated my original post.

[Timothy Rapson]

Jason, you math is off considerably.

Is it now? I based my calculations off this PPI tool (http://www.thirdculture.com/joel/shumi/computer/hardware/ppicalc.html), and I have no reason to doubt it's accuracy. If you can explain to me why this tool is wrong, please do.

Pocket PC with 3.5" screen: 114 ppi
Pocket PC with 3.8" screen: 105 ppi
Pocket PC with 4" screen: 100 ppi

Those number make sense to me - your numbers do not.

And the next OS is not called Merlin - that's what Pocket PC 2002 was called. :wink:

Yes, you were right about the PPC ppi, but the Sony's are not 220 ppi, they are more like 160, maybe 150

Oh, on the Merlin. I should have written Magneto.

[ctmagnus]

Is it now? I based my calculations off this PPI tool (http://www.thirdculture.com/joel/shumi/computer/hardware/ppicalc.html)

Does that work in PIE? It appears to resize to the right size but my iPaq's just been prepped for a return (ie, flipped the switch) so I am unable to check right now.

[Thinkingmandavid]

check this out, FUjitsu's 800*600 lcd http://www.theregister.co.uk/content/68/31748.html

[Jonathon Watkins]

Yup, we covered that last week:

http://www.pocketpcthoughts.com/forums/viewtopic.php?p=136825

[theone3]

if palm can do it... we can do it :wink: