QuickCam Team Forums

Hello!
I was guided here from general logitech forum (http://forums.logitech.com/logitech/boar...d.id=51573).

I have two problems, actually.

1) Webcam tends to overexposure for about 2 stops in automatic mode, so I can occasionally see pure white spot in place of my forehead. Manual exposure corrects this problem, but it's not convenient. It would be nice to see some extra slider in camera settings (+- EV, photo like).

2) When I capture video with VirtualDub via DirectShow, I get 640x480@30fps without a problem. The problem is in resolution. Pixels look doubled, like in picture stretched from 320x240. Other resolutions (320x240, 352x288, 960x720) look fine. Is this a software bug, or I'm just doing something wrong?

Thanks

I don't know why KachiWachi considers this "developer information", but let's see ...

If you try other capturing software (e.g. AMCap), do you see the same problem with 640x480?

This sounds like a driver related issue to me.

Again... This sounds like a driver related issue to me.


Thanks.

Yes. AMCap gives the same picture.
I studied the problem more closely and found that 960x720 is not true 960x720 either. Again pixels look doubled, but overall picture is more detailed (but fps is lower, of course).
Capturing via VFW gives true resolution though, but only at 15 fps.

Would you mind posting a screenshot of the "pixelated" image? I will try with the same camera and see if I can reproduce the issue.

Shure!
directshow:
[attachment=107]
vfw:
[attachment=108]

I couldn't really reproduce the problem although I did see some unsharp/pixelated images. However, it didn't look as if that was the result of upscaling. Actually, it seemed like 640x480 was not as sharp as 960x720 because the camera itself has to downscale the image.

Are you using the Windows in-box UVC driver or the Logitech one? (If the latter, which version?) If you use the Windows one you should make sure that you use YUYV instead of MJPG to reduce compression artifacts.

I'm using the lastest logitech driver (11.8). And I think, you didn't understand, what was shown at the pictures above: originally, both pictures are 640x480. I didn't scale them in any way. The only difference is that upper pic was forced @30fps, and bottom - @15fps. I also found, that capturing at 640x480@15 via directshow gives the save (good) picture as vfw @15.
So: 640x480@15fps - good image. 640x480@20(25-30) fps - pixelated.

Update: under WinXP SP2 UVC driver I just can't get more than 15fps at 640x480, no matter how I configure a capture pin.

Hello!
I'm starting the new thread because of replacing QuickCam S5500 with QuickCam 9000 Pro. This TOP logitech webcam has the same problem as 5500.
The problem:
I'm using VirtualDub to capture video from webcam. I found a huge difference in image quality depending on _selected_ framerate. Actual framerate doesn't matter. Setting 5-10-15 fps in a capture pin gives true 640x480 image. Force 20-25-30 fps and you'll loose details. RightLight may be turned on or not (so actual framerate can be 5, 10 or 30), but it doesn't matter at all. Picture looks like 320x240 upscaled to 640x480. The difference between S5500 and 9000Pro is in quality of scaling. :) 9000 looks smoother, but no more.

forced 15fps

forced 30fps


My system caps: WinXP sp2, Intel Core2 Quad system, P35 chipset, 2Gb ram.

PS. I found a guy, who noticed similar problem. Here is the url: skype forum

I'm combining the two threads because it's really the same topic, but I've changed the thread title.

Ok. Thanks. But I really want to know, if it's a driver bug or a hardware limitation.

It looks like we're able to reproduce the behavior. We're going to do some more analysis and then post back if we have any updates.

Thanks. I really hope, this is a driver bug...

The behavior you observed is unfortunately a hardware limitation that becomes visible at frame rates higher than 15 fps. It comes from the downscaling of the full sensor resolution, not upscaling from a lower resolution. For the QuickCam Communicate S5500 it is quite noticeable but for the QuickCam Pro 9000 it's hardly visible.

What can I say... I'm disappointed. I'm returning webcam back to the store and don't mess with logitech webcams anymore. I'll consider writing an article to iXBT explaining this nice "feature" to many of our readers.

Thanks for your time

What I am wondering is that does Logitech or some other manufacturer produce webcams, that can do at least 640x480 at 25-30 fps?

I would think, that normal users don't have much use for 1600x1200 at 5 fps. I personally get annoyed by the unreal picture also at 15 fps. This makes it kinda pointless to have 2MP or nice optics when all you see is about 400x300 of it at decent frame rates.

This complaining is not Logitech specific. In fact I think Quickcams might be the least bad of all the unsatisfactory consumer level webcams.

I think big and fast photo sensors and the circuitry needed for them are relatively expensive. Still now days there are consumer priced video cameras, that can *I think* give real progressive picture 30 fps and HD resolutions so why not make a webcam with that technology..

Most of our newer UVC webcams can actually do 640x480 at 30 fps pretty well. The problem is that some features like 'Auto-exposure' or 'Low-light boost' may sacrifice frame rate in order to get a better image quality. Image quality is a very subjective topic and different applications have different preferences.

We are aware of the fact that there is a high demand for 30 fps, so you will see more improvements in the future. In the meantime I can recommend you to play with the above settings. I've been wanting to write an FAQ about that topic for a while, I just need to find the time. Sorry for the delay! :-|

400x300 != 640x480.

And yes, auto-exposure needs to be disabled under most inside lighting conditions to get 30 fps.

And your point would be ...? :-)

The frame rate is generally independent of the resolution, at least for everything <= 640x480. At higher resolutions hardware and USB limitations start to have an influence as well.

Resolution at 800x600 at 15 fps:


Resolution at 800x600 at 25 fps:


The real resolution at requested resolutions above 352x288 at 20-30 fps is always at best about ~ 400x400. I think it might be 1600/4 x 1200/4 = 400x300, it would be logical considering the CCD is 1600x1200.