When Will We See More Than 16bit Colour?

[Jason Dunn]

I've been using a Dell Axim X50v lately (I switched back to it from the PDA2K) and as much as I love the screen, one thing about it still bothers me (other than the poor battery life): the fact that there's a crisp, high-contrast, beautiful VGA screen...capable of showing only 16-bit colour. For you non-math types, that's 64,000 colours. Odds are good that the computer you're sitting at reading this is displaying either 16.7 million colours (24 bit) or 4.3 billion colours (32 bit). Most computers have been at 24 bit colour or higher for the better part of a decade, so you may not remember what photos looked like in 16 bit colour...but I'm reminded of that every time I look at a photo or (especially) when I watch a video on the X50v. There just aren't enough colours to make the images/videos look like they're supposed to look. The colour banding is most evident with video files, but it's noticeable with photos as well - especially ones with a solid colour wall.<br /><br />I have my doubts as to whether this is going to change anytime soon, because I don't think very many people notice/care about it. So let's satisfy my curiosity with a survey, shall we?

[hoodmeister]

Christ all mighty, yes!

One of the biggest factors which put me off ever buying a PDA in the first place, was 16Bit displays.

Having seen them in action, they're not so bad... But I would kill for 24 / 32Bit...

I always put it down to LCD's being very expensive as it is, and therefore 32Bit displays being disproportinately expensive... But i'm not so sure on the matter.

I have an X50v, and it's just about the best PDA i've seen for mobile movie watching... I had quite a bit of tearing, for example, on my 2210. But movies still look lifeless and dull on a 16Bit display. It passes the time, but it always shocks me when i've been on a long train journey and then get back to a 32Bit workstation...

[IpaqMan2]

Oh, I'm sure I'll get stampede for my opinions, but there are many more things I would like to see the Windows Mobile platform incorperate before Micorosft , or OEMs focus on this. I mean if it would be an easy fix than I am all for it, but if it's going to cost them alot of time and research than I would like to see other things done, like adding 4 gigs of internal flash memory to all pockets or even a built in micro hard drive, oled screens, maybe even a tad bit larger screen so when viewing things in VGA or watching videos it could be a bit more pleasent to the eyes, even adding a really nice and functional TTS (Text To Speach) capibilites right into the OS that you can actually understand and sound remotely real so no matter what application I am using, email, avantgo, ebooks, or even maps with a GPS unit I could have information read to me while I am on the go, and than of course there is always the battery life issue which can always be worked on. Heck if we are wishing than while not have capibilities so you can record direct media such as videos from TV, and other source, much like the new Archos models. I would love to see a consumer focused Pocket PC model avalable.

But of course if all of these ideas will be neglected by Microsoft and their OEMs, than sure. I'd love to see more bits in Pocket PC displays.

just my thoughts.

[QYV]

This survey doesn't seem like it's asking the right questions. I mean, OF COURSE everyone wants 24-bit color rather than "not having it". But what are the tradeoffs involved?

IMHO, you'd want two separate surveys, as follows:

1.) How much more would you pay more for a 24-bit color screen?

2.) What is an acceptable % decrease in battery life for a 24-bit color screen?

I know I'd be interested in seeing those results...

[MasterOfMoo]

Without a doubt, YES!

I take a lot of photos and take advantage of using my Pocket PC to preview the digital output (a viewscreen on the camera is nice, but still small when trying to isolate quality in certain details).

Seeing the limitations in the Axim x50v (although it *is* glorious in comparison to my old iPAQ 3600) is frustrating.

[jerboa]

This survey doesn't seem like it's asking the right questions. I mean, OF COURSE everyone wants 24-bit color rather than "not having it". But what are the tradeoffs involved?

Very good point - I'd love 24bit colour but not if suddenly I find myself with a PDA that runs for an hour before needing a charge.

And if the price premium is significant, well, maybe I could not afford it anyways :)

[rob_ocelot]

Most computers have been at 24 bit colour or higher for the better part of a decade, so you may not remember what photos looked like in 16 bit colour...but I'm reminded of that every time I look at a photo or (especially) when I watch a video on the X50v. There just aren't enough colours to make the images/videos look like they're supposed to look. The colour banding is most evident with video files, but it's noticeable with photos as well - especially ones with a solid colour wall.


I think regular television is only 16bit colour depth in a practical sense, even though in theory an analog signal can have an infinite depth of colour. The banding you're seeing with videos may have more to do with compression/encoding than the limitations of the PPC screen.

If you're seeing a lot of banding in places where you know there should not be I'd check the dithering options in the player as well.

[surur]

I have my doubts whether I can see more than 65000 colours. The difference between 8 bit colour and 16 bit is certainly very dramatic, but 16 and 24 is not half as significant.

I would not prioritise this.

Surur

[Sven Johannsen]

Sure no problem, I'd love every graphic file to take 50% more space than it does now, just like I was thrilled at having 640x480 resolution so those files can take 4 times as much space. After all memory in PDAs is plentiful and dirt cheap.

BTW, I don't think it is actually an LCD issue, but more the driver componenets. We are still dealing with mixing three colors, each of which could be set to an infinitely variable brightness. It's the discrete brightness levels that are determined by the number of bits you use to encode that level that are the limitation. If you use 4 bits, your red pixels can be one of 16 brightnesses. Same for blue and green (12 bits in all), so you get 16 x 16 x 16 or 4096 possible combinations.

[Jason Dunn]

If you're seeing a lot of banding in places where you know there should not be I'd check the dithering options in the player as well.

Then why am I seeing it in photos? I've replicated the exact same effects on a desktop computer by switching it to 16 bit.

[JonnoB]

yes, it would look better... but be aware that with the bit-depth increased, video memory would need to be increased. Also, video data from the CPU to video controller would increase affecting overall performance. There would also be a hit against the battery. I think the system should support multiple bit-depths. Heck, many would be ok with a 2 or 4-bit monochrome display for some things and save memory and battery... then switch to color based on an application or setting.

[KTamas]

320×240@16 bit: one image - 150 kb
320×240@24 bit: one image - 225 kb
640×480@16 bit: one image - 600 kb
640×480@24 bit: one image - 900 kb
50% increase...
This would be a real performance hit i think. But yes, i want it :)

[njl2016]

Don't some of the newer PalmOne devices have 18-bit displays?

[Menneisyys]

The colour banding is most evident with video files

That's more of the problem of the decoder routines and/or the MPEG-based encoding AFAIK. (I'm not sure about this though - Picard may be able to give a more definite answer.) Furthermore, BetaPlayer allows for dithering (with some additional CPU usage), which does a decent job of hiding this effect.

but it's noticeable with photos as well - especially ones with a solid colour wall.

That's right - this effect does ruin wathcing images on a PDA. However, some image viewers allow for error diffusion dithering in 16 bit mode. F-S Album (coming with the Pocket Loox 720), XnView 1.20 ( http://www.xnview.com/ ), Aidem Pocket Painter 2.11
( http://www.aidem.com.tw/English/en_pocketpainter.htm ), Aidem Photo Explorer 2.01 ( http://www.aidem.com.tw/English/en_photoexplorer.htm ) and Applian Picture Perfect 5.1 ( http://www.applian.com/pocketpc/pictureperfect/index.php ) all support this mode (the latter being of the worst, image quality-wise). Unfortunately, the most "all-in-one" image viewers, Resco Picture Viewer 5.2 (haven't tested 5.3 in this respect as yet) and Spb Imageer 1.2 indeed don't support this.

So, I think 16 bits are enough even for people that use their PDA's as digital image wallets if you switch to using, say, Aidem Photo Explorer. (VGA PDA's, especially the Pocket Loox 720 and the iPAQ hx4700, are perfect for that.)

24 bits would indeed be welcome, but I think it would also introduce a considerable hit on the overall power on the device. Think of the case of the iPAQ 38xx: its computation power is about 15-20% less than the 36xx/37xx because it had a 16 bit screen, while its (faster) predecessors had only 12 bit-screens.

[hoodmeister]

I have my doubts whether I can see more than 65000 colours. The difference between 8 bit colour and 16 bit is certainly very dramatic, but 16 and 24 is not half as significant.

I would not prioritise this.

Surur

The second I sit down to a workstation running in 16Bit mode I can tell...

So i'd be forced to disagree with this. I maintain that 32Bit displays would make for an overall better PPC experience.

[Menneisyys]

If you're seeing a lot of banding in places where you know there should not be I'd check the dithering options in the player as well.

Then why am I seeing it in photos?

Dithering in photos also mean tradeoffs because it's by introducing some kind of random noise that dithering works. I've made some examples of this:

Resco, no dithering:
http://menneisyys.freeweb.hu/PICVIEWERS/index_tiedostot/image007.jpg

F-S Album, correct dithering:
http://menneisyys.freeweb.hu/PICVIEWERS/index_tiedostot/image008.jpg

Picture Perfect 5.1, pretty noisy and bad dithering algorithm:
http://menneisyys.freeweb.hu/PICVIEWERS/index_tiedostot/image010.jpg

As can be seen, especially the last shot has quite a lot of noise.

It's also worth noticing that the horizontal stripes on the guy's T-shirt are only visible on the Resco representation of the image; on the two other images are completely messed up. So, dithering not only introduces noise but also effects like this.

[Jason Dunn]

Comments about spelling moved here:

http://www.pocketpcthoughts.com/forums/viewtopic.php?p=341147

Please follow up there if you want to talk about spelling. ;-)

[Tye]

Oh, I'm sure I'll get stampede for my opinions, but there are many more things I would like to see the Windows Mobile platform incorperate before Micorosft , or OEMs focus on this. I mean if it would be an easy fix than I am all for it, but if it's going to cost them alot of time and research than I would like to see other things done, like adding 4 gigs of internal flash memory to all pockets or even a built in micro hard drive, oled screens, maybe even a tad bit larger screen so when viewing things in VGA or watching videos it could be a bit more pleasent to the eyes, even adding a really nice and functional TTS (Text To Speach) capibilites right into the OS that you can actually understand and sound remotely real so no matter what application I am using, email, avantgo, ebooks, or even maps with a GPS unit I could have information read to me while I am on the go, and than of course there is always the battery life issue which can always be worked on. Heck if we are wishing than while not have capibilities so you can record direct media such as videos from TV, and other source, much like the new Archos models. I would love to see a consumer focused Pocket PC model avalable.

But of course if all of these ideas will be neglected by Microsoft and their OEMs, than sure. I'd love to see more bits in Pocket PC displays.

just my thoughts.

Yeah! What he said! ^^^

It would be nice to see better screens, but there are *so* many other issues that need resolved first. And I do believe the memory hit wouldn't be worth it on such a limited platform.

[Jason Dunn]

Some interesting points on both sides - keep up the conversation. :-)

(I knew moving from 16 to 24 bit wasn't as simple as flipping a switch, but I was curious to see how many people actually noticed/cared about the limitations of 16-bit colour)

[Kowalski]

this realy depends on what you are expecting from a pocket pc.
some use their pdas to view images and watch videos. increasing color dept will surely add value to their pdas
i am pleased with 16 bit screens and dont want more because it will decrease battery life, increase the complexity of the device thus increase system load.

i mostly use my device with brightness set to 50% just to increase battery life. if i had a chance to decrease the display colors to increase the battery life, i would do that for sure. 256 colors(8 bit) will do just fine for pim applications which is my primary use of pda.

vga resolution is an improvement for sure, and decreases the runtimes greatly, but adds a great value to usability. more text can be squized to the same physical dimensions. in the end i will give up some runtime to increase the usibility of my device but increasing color dept wont add any value for me. my vote goes to no!

[Camp]

The BenQ P50 was supposed to have an 18-bit display (and would still have been the first PPC) and this is one of the main reasons that I wanted this device so bad. When I compare my JAM's 16-bit screen witht he 18-bit screens that some cellphones have, I can see the difference, and I think it makes a major difference. Too bad the P50 is becoming the next MPx...

[Pony99CA]

I don't remember where I saw this, but I recall reading that increasing the color depth can actaully improve pictures more than increasing the resolution. This was probably from the 80s, so maybe they were talking about going from 8-bit to 16-bit color or 16-bit to 24-bit color on PCs, but I don't know what resolutions were being compared.

Steve

[surur]

Here is two screen captures of my desktop. There is some very minor changes in the gradients, but its not really terribly noticable.

http://www.pocketpcthoughts.com/media/users/4259/32bit.PNG
32 bit

http://www.pocketpcthoughts.com/media/users/4259/16bit.PNG
16 bit

Its highly unlikely the interface would change or benefit in any way.
Its saved in png (which is 24 bit I think), but it should at least differentiate between 16 bit and 24 bit on the pocketpc.

Surur

[Fishie]

Sure no problem, I'd love every graphic file to take 50% more space than it does now, just like I was thrilled at having 640x480 resolution so those files can take 4 times as much space. After all memory in PDAs is plentiful and dirt cheap.

BTW, I don't think it is actually an LCD issue, but more the driver componenets. We are still dealing with mixing three colors, each of which could be set to an infinitely variable brightness. It's the discrete brightness levels that are determined by the number of bits you use to encode that level that are the limitation. If you use 4 bits, your red pixels can be one of 16 brightnesses. Same for blue and green (12 bits in all), so you get 16 x 16 x 16 or 4096 possible combinations.

Thats bull and you know it.
The size of your digicam pics isnt gonna increase becouse suddenly the PPC OS can handl more colours, they will remain the same regardles if your screen is 8 shades of grey or uses true colours.
Likewise, games will continue to use 16 bit colour textures or whatever.

[MitchellO]

Even if they start by going to 18-bit (262k colours i think) colour, it would be better. I mean, the new tungsten t2 has is (with 320x320), why can't PPCs? Do any PPCs have 18-bit colour?

[Kursplat]

It would be especially nice if the OS supported changing the color depth easily. Imagine being able to assign color depths to different applications. That way, when you switch to your picture or video viewer, the system automatically adjusts to 24-bit. Reading an eBook? Black and white. PIM? 256 colors.

This makes maximizing battery life by adjusting the color depth like throttling back the CPU except when you need it.

If I had to go to a configuration screen (or heaven-forbid do a soft reset) every time I wanted to change the color depth, I would probably stick with 16-bit as a compromise for regular use.

[Jason Dunn]

It would be especially nice if the OS supported changing the color depth easily. Imagine being able to assign color depths to different applications. That way, when you switch to your picture or video viewer, the system automatically adjusts to 24-bit. Reading an eBook? Black and white. PIM? 256 colors.

Awesome idea! :way to go:

[rob_ocelot]

If you're seeing a lot of banding in places where you know there should not be I'd check the dithering options in the player as well.

Then why am I seeing it in photos? I've replicated the exact same effects on a desktop computer by switching it to 16 bit.

There's a number of factors in play that make the resuting picture look banded, and IMO they are somewhat different for videos than they are for photos.

First off, The videos you are watching on a PPC have to be changed in resolution for display, either by the PPC itself or by prerendering on a PC. For QVGA devices that means you have to merge 4 pixels into one hybrid pixel that is representative of the 4 -- and you've already introduced what will look like colour banding without taking into account the difference in colour depth between the original video and the display device.

Secondly, colour TV (at least NTSC) has historically been a bit of a kludge to keep it compatible with B&amp;W sets. Our eyes and brains are physiologically more responsive to light and dark than they are to colour and as a result colour TV uses a full resolution (640 x 480 interlaced) B&amp;W signal with an astonishingly lo-res colour singal overlayed on top of it. Our brains do the rest of the work and fill in where the colour "should" be -- and the result looks to us like a hi-res colour TV picture. This worked great for many years until the advent of digital encoding and decent computer displays which can accurately determine each pixels colour and do it without interlacing. Today's displays (including Pocket PC's) are so much better than standard definition TV's that you see just how limited the colour information in the original TV signal is. As a result, computers have to fudge what was never in the original analog signal in the first place and quite often a computers 'best guess' looks awful to human eyes.

Going to 18 or 24 bit colour probalby wont change very much for videos viewed on the PPC screen as the color depth *that was not there to begin with* will have to be approximated by dithering or other algorithims.

Looking at just how expensive and thick VGA Pocket PC's are (so thick that they more often than not include a CF slot to make it look like it's *supposed* be that thick) the added circuitry would add some more to that.. Larger power requiements mean that standard battery capacities need to be bigger or consumers will bitch (if the X50V is anything to go by). It all ends up costing us more money.

I haven't seen any of the dedicated video players up close to determine if they use 16 or 24 bit displays, but I'm definitely curious.

[MitchellO]

I think the PMCs only have 16-bit colours. Its amazing that phones has 18bit colour but PPCs don't yet!!

[gibson042]

Okay, time out!

While there is definitely more data in a 32-bit color depth than a 24-bit, I was under the impression that the added information was an alpha channel (transparency/opacity) and did not create any new colors. Am I mistaken? Have panels that can produce 4.3 billion distinct colors been developed and slipped right under my nose? Engadget seems to confirm my view (http://www.engadget.com/entry/7312188229818511/, http://www.engadget.com/entry/3611628861772596/, http://www.engadget.com/entry/1498507751662585/).

Time in.

Pedantry aside, color depth seems like a minor issue on PDAs, and should have a correspondingly low priority. I'd love to have desktop quality colors, but I'm not even willing to pay more for 18-bit, let alone 24. And given the 50% increase in graphics throughput that would be required just to match the performance of existing devices, it doesn't seem at all realistic in the short term. Maybe it will in four or five years. And by then I'll be clamoring for it, assuming the current volatile/persistent storage and battery issues have been resolved.

[Kursplat]

Thats bull and you know it.
The size of your digicam pics isnt gonna increase becouse suddenly the PPC OS can handl more colours, they will remain the same regardles if your screen is 8 shades of grey or uses true colours.
Likewise, games will continue to use 16 bit colour textures or whatever.

That's not total bull, whether you know it or not.

You are correct that the camera pics won't grow in size and neither will video files, but the icons and graphics in the OS and applications that are rendered in 24-bit instead of 16-bit WILL grow. When you switch your XP resolution to 24-bit, the icons don't stay 8-bit (or 16-bit), do they?

What makes you think PDA games would continue to use 16-bit color if PDAs go to 24-bit? That's like saying desktop games are still 256-color even though the systems support 24-bit color If a significant number of PDAs start offering 24-bit support, don't you think the game authors will take advantage of that? Of course, not ALL games would become 24-bit, just like not ALL desktop games are 24-bit. But enough of them will.

Not that games with 24-bit graphics is a bad thing. Only, they need to follow longer battery life, more memory, and faster CPU/GPUs to handle the graphics. I suspect most PDAs would choke on 24-bit DOOM. And what good is it if you can only play it multi-player via BlueTooth for 10 minutes before the battery runs out?

[Menneisyys]

Going to 18 or 24 bit colour probalby wont change very much for videos viewed on the PPC screen as the color depth *that was not there to begin with* will have to be approximated by dithering or other algorithims.

I haven't seen any of the dedicated video players up close to determine if they use 16 or 24 bit displays, but I'm definitely curious.

Yesterday when I left home it occurred to me that I've even read a book on video encoding: Video Demystified (Demystifying Technology) from Keith Jack (Newnes). Just looked up the relevant info; MPEG-based compression algorithms use very few bits to encode the color space to reduce bandwidth usage. Therefore, more color depth won't help at all the video banding problem; the only way to go is dithering while playing.

[Albegor]

yes, it would look better... but be aware that with the bit-depth increased, video memory would need to be increased. Also, video data from the CPU to video controller would increase affecting overall performance. There would also be a hit against the battery. I think the system should support multiple bit-depths. Heck, many would be ok with a 2 or 4-bit monochrome display for some things and save memory and battery... then switch to color based on an application or setting.

Sure it would look better, but I completely on the technical issues involved, especially the bith-depth switching capability.
Who knows, maybe we'll see the first implementations in WM2005 Second Edition... :dilemma:

[Duncan_Idaho]

There is one Pocket PC with 24bit screen on the market. This is InView Navi 911 known also as Palmax z720. It has WM 2003 SE, X-Scale PXA263 300MHz, 128MB RAM, USB host and integrated GPS. You can buy it in europe.

This is a review of the first version, without some of the features, as 24bit screen.
http://mobile-review.com/pda/review/palmax-z720-en.shtml

[MitchellO]

where did you see 24bit? In the review, and the specs at the bottom it says it shows 65K colours.

The display is similar to other Pocket PCs. It doesn’t have any peculiairutes among other displays with the resolution of 320x240 pixels. Transflective display (diagonal is 3.5) can show up to 65000 colors, the comfortable view angle is up to 45 degrees. The lowest level of the backlighting allows to work with the PDA in the dark, to read books, for example. The information on the screen is visible in the sunny day, it is faded but remains quite distinguished.[/b]

[Menneisyys]

where did you see 24bit? In the review, and the specs at the bottom it says it shows 65K colours.

The display is similar to other Pocket PCs. It doesn’t have any peculiairutes among other displays with the resolution of 320x240 pixels. Transflective display (diagonal is 3.5) can show up to 65000 colors, the comfortable view angle is up to 45 degrees. The lowest level of the backlighting allows to work with the PDA in the dark, to read books, for example. The information on the screen is visible in the sunny day, it is faded but remains quite distinguished.[/b]

Yeah, it seems to be a spiced-up Mitac Mio 168, which seemingly hasn't been released to the international market - the review was written on 14 July 2004 and all the references to it are mostly in Russian.

[Craig Horlacher]

I've only skimmed through here but wanted to point out a few things.

Concurrent display of colors and colors available in the palette to be displayed have not always been the same. In other words, it's possible that a device has a palette of 16.7 million collors but is only able to display 65k at a time. If the screen resolution is 240x320 then you've only got 76,800 pixels you can light up in different colors. In that case, 65k is almost enough to have each pixel be a different color. In theory, the extra colors added by a 16.7 million colors wouldn't make that much of a difference since it's only 11 more colors that can be different and the chance of every pixel being a different color is slim.

If your screen is 480x640 things do change...you now have 307,200 pixels to deal with. In this case 65,000 colors is *less-than-one-quarter* of the total pixels. That means there will be a lot of pixels that have to be the same color. This could render ugly banding or just inacurate colors on photographs.

If you're doing 640x480 video on your pocket pc - well, that's up to you. I've found that on a 4" display 320x240 is very adiquate to not only look very good but still drop the jaws of anyone I show it to who doesn't know what pocket pc's can do.

So, I'm really indifferent on the color depth for 240x320 devices. I do think that it makes a lot of sense to bump 480x640 devices up a notch!

I also, want to agree to some extent that the application used and it's settings can make a big difference on how the image looks.

[Sven Johannsen]

Thats bull and you know it.
The size of your digicam pics isnt gonna increase becouse suddenly the PPC OS can handl more colours, they will remain the same regardles if your screen is 8 shades of grey or uses true colours.
Likewise, games will continue to use 16 bit colour textures or whatever.

That's not total bull, whether you know it or not.

You are correct that the camera pics won't grow in size and neither will video files, but the icons and graphics in the OS and applications that are rendered in 24-bit instead of 16-bit WILL grow. When you switch your XP resolution to 24-bit, the icons don't stay 8-bit (or 16-bit), do they?



Thanks for popping in there. That's really what I was referring to; the graphic artifacts within the OS. Sure you can load 1280x1024 x 16M color picture files on your PPC if you want. It doesn't matter if it can display it or not. Point is that having that capability of displaying it inherently takes more video memory. When you move from 16 to 24 bits that is a 50% increase in bits, and from 320x240 to 640x480 that's a 400% increase in bits that must be stored, processed and moved.

[Zman]

This would look great but most likely not be worth the performance cost.

with 4 bit color (1 byte per 2 pixels) we process 320x240/2 = 38k
with 24 bit color (3 bytes per 1 pixel) that would be 320x240x3 = 230k

so to process that many pixels would require 6x the bandwidth to acheive the same framerate, would you accept the increased color if it meant your video or game went 5fps rather than 30fps? this is only looking at 1 technical aspect, on the marketing side of things the PPC has always been a business users device, so unless business users would need 24 bit color most manufacturers aren't going to add it.

the jump to VGA is a much better upgrade than 24b color imo (and in the hardware manf opinions apparently), with the pixel size being so small on a VGA screen dithering is much less of a noticable problem.

[Zman]

Thats bull and you know it.
The size of your digicam pics isnt gonna increase becouse suddenly the PPC OS can handl more colours, they will remain the same regardles if your screen is 8 shades of grey or uses true colours.
Likewise, games will continue to use 16 bit colour textures or whatever.

That's not total bull, whether you know it or not.

You are correct that the camera pics won't grow in size and neither will video files, but the icons and graphics in the OS and applications that are rendered in 24-bit instead of 16-bit WILL grow. When you switch your XP resolution to 24-bit, the icons don't stay 8-bit (or 16-bit), do they?



Thanks for popping in there. That's really what I was referring to; the graphic artifacts within the OS. Sure you can load 1280x1024 x 16M color picture files on your PPC if you want. It doesn't matter if it can display it or not. Point is that having that capability of displaying it inherently takes more video memory. When you move from 16 to 24 bits that is a 50% increase in bits, and from 320x240 to 640x480 that's a 400% increase in bits that must be stored, processed and moved.

I don't think the storing of the bits a problem at all, as most devices have plent of memory these days, and the x50v has a dedicated 16MB frame buffer! it is more a problem of memory bandwidth (the processing and moving) that you speak of.

[Talon]

Most PDA displays are currently 18 bit colour (6 bits for each colour), there is no reason other than cost why they aren't 24 bit. Unfortunatly most older PDA CPUs only included support for 16 bit displays (normally 5 bit red and blue, 6 bit green).

The Bulverde (Xscale 27x) can in theory support 24 bit displays but it's going to add cost, in such a price driven market I'd expect most devices to become 18 bit simply because it's cheaper than 24.

From what I can remember about how your eye works 24 bit is getting close to the maximum number of colours you can see, any more than that is going to be wasted on a lot of people and probably not worth the effort / cost / power.

[twalk]

Just stepped in and seen this.

To clear up some things from previous posts:

There are 3 major processes for making panels. Each type has it's benefits and drawbacks as far as the final product's performance goes. 2 of them make 18 bit screens, the other is 24 bit. The 24 bit screens are more expensive and slower than the other 2. (The 18 bit screens still take in 24 bit color data, and then map and interpolate.)

I don't know of any current PDA that actually uses more than 16 bit color. On an 18 bit screen that means the PDA uses only 1/4 the color spectrum available. Normally this is a direct color map (no pallete), meaning that those other colors are totally inaccessable. (Cheap 18 bit would send 16 bits to the video controller, which would then interpolate to get the other colors.)

16 -> 24 means 50% more storage space is needed, but normally also means that 100% (2X) more run time memory is needed for graphics. That's because programs normally use 32 bits to store every 24 bit value for speed.

PalmOS 5 cannot handle more than 16 bit graphics, period. If you heard of 18 bit support, you heard a false rumor. (It's an API thing. PalmOS 6 works fine with 24 bit.)

The only significant tradeoffs that 16 -> 24 would have is speed and cost.

(From what I can remember...) The human eye can distinguish different colors to about 26/27 bit color.

24 bit color on a 320x240 screen will still look better than 16 bit color on it, unless the 16 bit color works from a 24 bit pallete.

Todd

[allenalb]

i would not want such a good screen, unless a 40gig hdd was also included :)

[Pony99CA]

This would look great but most likely not be worth the performance cost.

with 4 bit color (1 byte per 2 pixels) we process 320x240/2 = 38k
with 24 bit color (3 bytes per 1 pixel) that would be 320x240x3 = 230k

so to process that many pixels would require 6x the bandwidth to acheive the same framerate, would you accept the increased color if it meant your video or game went 5fps rather than 30fps?
Your math is good, but your facts are flawed. What PDA today uses 4-bit color? Didn't that go out with Windows CE 2.0 or so?

Most PDAs that I'm familiar with use 16-bit color, so 24-bit color would only require 50% more bandwidth (100% more if pixel data was stored in a 32-bit value). That would be a drop of 33-50% in screen performance, not the 87% you mentioned.

However, remember that we had 16-bit color using 206 MHz processors in the past. Many PDAs are now running at 400 MHz, with some running at 624 MHz, so the processing power should be there to handle the additional load. (I don't know whether memory access speed has increased, though.)

the jump to VGA is a much better upgrade than 24b color imo (and in the hardware manf opinions apparently), with the pixel size being so small on a VGA screen dithering is much less of a noticable problem.
That's an interesting claim. VGA requires four times the bandwith of QVGA for the same color depth. If they truly make use of VGA resolution, that's a 75% reduction in screen performance over a QVGA display. So how is that a better upgrade than going to QVGA 24-bit displays as far as performance goes?

I suspect one reason manufacturers did that wasn't because VGA was truly a better upgrade, but because an increase in screen resolution is more marketable than an increase in color depth.

I don't know which is cheaper to make, though -- 24-bit QVGA displays or 16-bit VGA displays. That would certainly affect a manufacturer's decision, too.

Steve