Jason Dunn
06-15-2004, 05:30 PM
<i>This article was written for Pocket PC Thoughts, but I thought it would interest anyone who creates video content for portable devices.</i><br /><br />I'm a big <a href="http://www.digitalmediathoughts.com">digital video enthusiast</a>, so I dream in 8000 Kbps data streams. 8) I'm a big stickler for quality, and I'm always pushing the limits on the quality of video playback on mobile devices. So the issue of video quality on the Pocket PC has been bugging me for a long time. I've ignored it/put off testing it for several years, but when I was testing the video playback on the X30 (it's awesome for video!) I had enough of this issue decided to dig deeper. <br /><br />So here's what I did: I took the same video clip and played it on my Pocket PC and on my desktop PC. The desktop PC was set at both 16-bit and 32-bit colour, while the Pocket PC was in the only mode it has: 16-bit. The sample is below, and depending on how sensitive you are to these things, you'll either notice the problem right away or wonder what I'm talking about... :lol:<!><br /><br /><img src="http://www.pocketpcthoughts.com/images/web/2003/wmp-quality-small.jpg" /> <br /><br /><span><b>So What Are We Looking at Anyway?</b></span><br />The video sample in question is 320 x 240, 24-bit colour, and at a 250 kbps data rate. I took the screenshots for the desktop computer with the video playing in Windows Media Player 10 Technical beta. For the Pocket PC, I was playing the video on the Dell Axim X30 and I took a screen capture using <a href="http://www.soti.net/default.asp?Cmd=Products&SubCmd=PCPro">SOTI Pocket Controller</a>. I was initially concerned that Pocket Controller was changing the video image, but I compared the screen shot with the video on the Pocket PC screen and they look identical.<br /><br />So what do we see in these images? The 32-bit desktop image looks perfect, because the video source is in 24-bit colour and there's enough colours to display it properly. When the desktop PC is in 16-bit colour mode, you can see some visual distortions, commonly called "banding". Gradiated colour is notoriously difficult to reproduce accurately if you don't have enough colours to work with. The Pocket PC is in 16-bit colour, so it should look the same as the desktop PC sample in 16-bit colour, right? Unfortunately that's not the case.<br /><br />The Pocket PC sample looks significantly worse than the 16-bit desktop sample. The banding is much worse - it's almost as if it's not really 16-bit colour! The differences are even more apparent <a href="http://www.pocketpcthoughts.com/images/web/2003/wmp-quality-big.jpg">on the bigger version</a> of the sample I created. I'm still in the process of searching for the right power charger for my 12-bit colour XDA in order to do some testing, because I'm beginning to think that Windows Media Player is displaying the video in 12-bit colour. That's only 4096 colours as opposed to the 65,000 colours that 16-bit colour has to offer.