re: load brightness, videoconferencing
Subject: re: load brightness, videoconferencing
From: Paul Chinn <firstname.lastname@example.org>
Date: Mon, 22 Jan 1996 17:19:21 -0800
From 1000klub.com!loomer Mon Jan 22 20: 15:44 1996
Organization: 1000Klub Software
Ken Edwards writes:
> I have nothing to back this up, but I always assumed that this was due to the
> fact that the user domain driver can have its time-slice cut in the middle of
> talking to the camera.
> Does anyone know if the same thing happens with the kernel device driver?
Time slicing should not cause the kind of flashing I am seeing which is:
every so often a frame whose entire brightness is significantly greater
than normal frames. I have timed these frames and the difference from a
normal frame is a couple milliseconds. If timeslicing was causing the
problem, we'd see things like brightness changing part way thru the
image and it splotches or bands. Plus, consider windows 3.1 which has
no preemption yet QuickMovie yields a stable image.
I think that we are missing something in the handshake or command
sequence. Scott Laird's library issues a complete reset between frames
which provides image stability but kills the frame rate. I used Thomas
Davis' routines for xfqcam but "out of the box" I could not get
continuous images. So I experimented with various combinations of
handshakes before and after reading the image. By luck I found some
that worked and allowed great fps, so that's what I used.
At this time I suspect any linux qcam software is either using Scott's
full reset or my code....but I don't think either method is entirely
correct and we need to look into this more.
> BTW: Paul Chinn also wrote:
> > massive strides the past few weeks. We've got a lot now: snapshot
> > scripts, interactive viewers, video conferencing, even the elusive
> Did I miss NV and VIC on the list, and does anybody know where they can be
I got nv to work with quickcam, but since I didn't know TCL, could not
add controls to set anything. A list member named Peter Grehan
<email@example.com> has a complete version though, and I understand VIC
as well. Perhaps he can speak up and let people know where to get it.