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

Thoralf Schulze thoralf_schulze at yahoo.de
Sat Mar 10 19:21:29 CET 2007


hi there,

i'm trying to get a high-resolution live feed into
gem. since using a dv camera is not a viable option
(frame rate to low, cpu consumption to high), i
decided to give some usb webcams a go.

unfortunately, things seem to look even worse here.
quarter-vga resolutions are no problem, but for higher
resolution (i settled for 640x480), the choices are
rather limited ... for the cheap ones, there are just
no v4l/v4l2-drivers available. i have a logitech
quickcam pro 5000 for evaluation right now - while
this one works relatively okay with the libuvc driver
(which provides a v4l2 interface), i cannot get it to
cooperate with gem. creating a pix_video object
triggers the following messages on the shell:

vidioc_s_crop: Invalid argument
VIDIOC_S_FMT: Invalid argument

and these in the pd window:

video driver 0: video4linux2
video driver 1: video4linux
video driver 2: ieee1394 for linux
startTransfer: 0
start transfer
device: /dev/video0
wanted 6408, got 'RGB4' 
error: should exit!
error: unknown format 'MJPG'
changed size from 64x64 to 320x240
buf.index==0
buf.index==1
buf.index==2
buf.index==3
format: MJPG -> 6408
colorconvert=1
waiting for thread to come up
waiting for thread to come up
waiting for thread to come up
GEM: pix_video: Opened video connection 0x6

looking at the source of the driver, there is the
following remark in uvc_driver.c:

 * The driver doesn't support the deprecated v4l1
interface. It implements the
 * mmap capture method only, and doesn't do any image
format conversion in
 * software. If your user-space application doesn't
support YUYV or MJPEG, fix
 * it :-). Please note that the MJPEG data have been
stripped from their
 * Huffman tables (DHT marker), you will need to add
it back if your JPEG
 * codec can't handle MJPEG data.

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. is there any chance of
getting this cam to work, anyway?
if no, do you know of any affordable webcams that go
along well with gem on linux and deliver 640x480 with
25 fps?

thank you for your help,
thoralf.


		
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