[GEM-dev] webcam logitech quickcam pro 5000 w/ linux

[Mathieu Bouchard]

On Sat, 10 Mar 2007, Thoralf Schulze wrote:

> for the cheap ones, there are just no v4l/v4l2-drivers available. i have 
> a logitech quickcam pro 5000 for evaluation right now

You might be better off using older QuickCams supported by the pwc.ko 
driver. The uvc driver is still very new, and last time I checked, it 
seemed a bit flaky, though maybe this has already changed (?).

> * The driver doesn't support the deprecated v4l1 interface.

Exactly. That's my main problem with it. My software is still v4l1 only. 
V4l2 is in the plans, but it's only in the plans. Now my main incentive 
for v4l2 is the quickcam pro 5000, though I don't have any. There's 
supposed to be an automatic adapter from v4l2 to v4l1 afaik, but it 
doesn't work in this case, i don't know why. Just because the interface is 
deprecated doesn't mean most programs still rely on it.

> * and doesn't do any image format conversion in software.

This is a policy of the linux kernel. Basically, Linux doesn't care that 
colorspace its interface is difficult to use directly, so all the burden 
is on the user, and because the whole thing is based on ioctl, it's 
essentially not possible to emulate it as a user-space library without 
redefining ioctl to be something else, so as far as V4L2 goes, there's no 
difference between the user and the userspace, because it's just a kernel 
interface.

> If your user-space application doesn't support YUYV or MJPEG, fix it
> :-)

This basically means that V4L2 is difficult to support because one is 
supposed to be supporting all of its color models. (Is it me, or the 
smiley makes it sound worse than without a smiley?)

> sending a |colorspace YUV( to pix_video does not fix it ... so i assume 
> that uvcvideos YUYV colour space is not the same as gem's YUV.

The V4L1 header alludes to the sarcastic quote "The nice thing about 
standards is that there are so many of them" in reference to the multitude 
of YUV bit-level formats - YUYV, UYVY, etc.

> if no, do you know of any affordable webcams that go along well with gem 
> on linux and deliver 640x480 with 25 fps?

The quickcam 4000 pro stops at 15 fps for that resolution. At 320x240 it 
goes up to 30 fps but limited to increments of 5 fps.

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| Mathieu Bouchard - tél:+1.514.383.3801 - http://artengine.ca/matju
| Freelance Digital Arts Engineer, Montréal QC Canada