[PD] pdp v4l problems

Andrew Cavers andrew.cavers at gmail.com
Mon Jun 13 17:47:24 CEST 2005

Hi list.

My first posting! I've only recently started using PD. I'm trying to
get some basic motion detection working using PD+PDP+PiDiP. Anyway,
I'm new to Linux as well so I thought I was doing well when I got PD +
PDP + my webcam (a Logitech Quickcam 4000 Pro) working.

But... The problem is with the webcam - it works perfectly in other
webcam software using the pwc drivers. However, whenever I try and use
it in PD, about once a second I get some black interference across the
image for a few frames. When PDP initiates the device it says that it
is set at 27 fps. There doesn't seem to be any way that I can alter
this and I suspect that this is the root of the problem. PDP is
supposed to have special options for pwc cameras such as mine but it
seems to just override any fps/resolution settings I set when I load
the pwc module.

I found the message below in the archive from over a year ago from
somebody apparently having the identical problem. Unfortunately it
went unanswered.

I'm using PD 038.4, PDP 0.13 on Slackware 10.1 (kernel 2.4.29) on x86.

Thanks for any help!


Copied message below:


I am not sure where to file pdp related bugs, so I am reporting some issues I
face to you. Maybe someone can help me out?

System info: Debian Kernel 2.6 on x86 with pwc/pwcx modules enabled, pd0.37-1
tarball, latest pdp tarball from your website, Philips 740 webcam. I am
basically new to pd.


Using pdp_v4l connected to a xv sink, vl4 device open succeeds, but

 * with a framerate of 27(!)fps.
 * the captured input is rendered greyscale instead of in color and with
extremely overloaded brightness level.
 * display gets interrupted by a 100ms black gap every second or so - guess
thats related to the 27fps? I get this distortion/gap-jitter combination even
with metro settings ranging from 10 to 300. After shutting down pd and
opening the cam again with camstream I _still_ see the gaps, then by
resetting cam-settings I get my cristal clear colored 25fps back.
Consequently I disabled direct pwc-support in pdp and recompiled, without luck
- pdp_v4l still seems to change pwc specific cam-settings. The PDP readme
mentiones included "special" pwc-support. What does that mean/do? And how can
I disable that except of the configure --disable-pwc option? The cam runs
flawlessly in every other v4l compiant application on my system (camstream,
 * sending a "close" message to pdp_v4l doesn't release it's device.
 * sending pdp_v4l a "type" msg yields a "no method for 'type'" warning and
does basically nothing.

Before I run to the next store to get me another cam, is there a way to
resolve (at least) the image distortion and "black-gaps interruption"-sync
issues? Or is there someone around doing reliable v4l-capturing and could give
me some hints on how to setup.

Best Regards,
Thomas Comiotto

Andrew Cavers
andrew.cavers at gmail.com

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