06-15-2004, 05:00 PM
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Executive Editor
Join Date: Aug 2006
Posts: 29,160
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Video Playback Quality: Does This Annoy Anyone Else?
I'm a big digital video enthusiast, 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.
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:
So What Are We Looking at Anyway?
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 SOTI Pocket Controller. 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.
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.
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 on the bigger version 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.
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06-15-2004, 05:28 PM
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Thinker
Join Date: Aug 2006
Posts: 439
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I'm kind of the opposite, I try to get the file size as small as possible. I make every effort to make sure the video is still watchable.
I see the distortion you're talking about, but it doesn't really bother me in the slightest. When I can fit four or five full length movies on my 256MB SD card, that's an accomplishment.
Maybe the difference is in how it gets rendered. Maybe the PC dithers with the 16 bit and the PPC doesn't.
Robb Bates
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06-15-2004, 05:39 PM
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Thinker
Join Date: Apr 2002
Posts: 437
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Hey Jason,
Have you tried counting the colors in the images to test your theory?
I tried doing it myself by croping the "big" sample you posted, but due to the JPEG compression, I was getting highest color counts for the worst images.
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06-15-2004, 05:42 PM
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Executive Editor
Join Date: Aug 2006
Posts: 29,160
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Quote:
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Originally Posted by R K
Have you tried counting the colors in the images to test your theory?
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How would I do that? I don't think my photo software has a "colour counter".
Quote:
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Originally Posted by R K
I tried doing it myself by croping the "big" sample you posted, but due to the JPEG compression, I was getting highest color counts for the worst images.
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The big image is actually a PNG file so there's no lossy compression, but it's a 24-bit PNG, so that might muddy the issue somewhat.
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06-15-2004, 06:27 PM
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Pontificator
Join Date: Mar 2004
Posts: 1,479
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Simple, dont use WMP, recode the vids for Betaplayer
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06-15-2004, 06:29 PM
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Intellectual
Join Date: Jan 2004
Posts: 119
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I'm not certain what you're expecting in terms of quality given the portable medium you're trying it on. Limitations and Portability go hand in hand, so given what we have to work with, I think that a level of adequate quality can be achieved, even for the most stringent purveyors of quality.
Since you think higher bitrates are sexy, have a go with BetaPlayer, it handles high bitrate avi's with relative ease. I would recommend encoding in Xvid with B-Frames on, the level of quality you can retain is very nice. Additionally, you should find a link on the same page for encoding software, PocketDivxEncoder, which outputs avi's formatted specifically for the PPC.
I would be interested to see what your results are using a media player other than WMP.
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06-15-2004, 06:30 PM
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Magi
Join Date: Feb 2002
Posts: 2,386
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Just judging from that image, there is no doubt that less colors are being rendered on the PPC. At first it looks like the two systems just may be dithering the image in different ways, but looking closer at the larger images suggest something else.
If you look at the 16-bit PC image (the large image), you can see 2 types of banding: a moire type of banding radiating from the sun and a "sun-ray" type of banding (only noticeable on the large image). Well, the "sun-ray" banding is less noticeable on the PC because there are far more bands... meaning a larger pallette of colors are getting used. Looking at the PPC version, the "sun-ray" bands are larger and more blocky... meaning less colors. There is also no moire pattern on the PPC image except for the area right above the sun where a few large "moire bands" exist.
Even if you look at the strand, the shadows are much more gradual on the PC version.
There's no doubt in my mind that the PPC image is using less colors... I wouldn't be surprised if that truly is 12-bit color.
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06-15-2004, 06:35 PM
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Executive Editor
Join Date: Aug 2006
Posts: 29,160
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Quote:
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Originally Posted by Fishie
Simple, dont use WMP, recode the vids for Betaplayer
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If you're suggesting that the colour banding is because of the video format (WMV), that doesn't make any sense - the video file is of pristine quality and looks great on the desktop. If the limitation is the 16-bit colour on the Pocket PC, all video players will have the same problem. If, however, the problem is with WMP, then another player might do the trick. I'll check it out!
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06-15-2004, 06:36 PM
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Thinker
Join Date: Apr 2002
Posts: 437
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Quote:
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Originally Posted by Jason Dunn
How would I do that? I don't think my photo software has a "colour counter".
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Sorry. I assumed that almost any photo editing software would come with a color counter, but after I took a look at some of mine, I found that to be a false assumption.
If you don't mind downloading some software, a freeware image viewer called <a href=http://www.irfanview.com/>IrfanView</a> can count colors in images. It's pretty safe to use, as it gives you clear control over file associations from the setup program.
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06-15-2004, 06:37 PM
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Executive Editor
Join Date: Aug 2006
Posts: 29,160
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Quote:
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Originally Posted by x999x
I'm not certain what you're expecting in terms of quality given the portable medium you're trying it on. Limitations and Portability go hand in hand...
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Sure, I'm very much aware of that, but I don't think I'm asking for all that much: I just want great quality video. :-)
Quote:
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Originally Posted by x999x
Since you think higher bitrates are sexy, have a go with BetaPlayer, it handles high bitrate avi's with relative ease. |
This has nothing to do with bit rates - the X30 can play WMV files at 1000 kbps. This is about colour dithering, and perhaps a flaw in WMP.
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Linear Mode
