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Re: [pwc] Re: Webcam button

To: Andrew Cavers <>
Subject: Re: [pwc] Re: Webcam button
From: Patrik Jakobsson <>
Date: Sun, 24 Jul 2005 13:44:38 +0200
Hi, I am glad you liked it.
It is wierd that you got that warning in pwc-uncompress.c because I
never touched it!
When I wrote the patch I worked with the source from the 2.6.12.2
kernel, this isn't the
latest version (maybee it doesn't have compression enabled) so I applied
my code to
the latest source and now it all works again.

You can get the new source from
http://www.shell.linux.se/xpatrikx/files/pwc-10.0.7a-snapshot.tar.bz2
or the patch to the 10.0.7a source at
http://www.shell.linux.se/xpatrikx/patches/pwc-10.0.7a-snapshot-patch

--Patrik Jakobsson

Andrew Cavers wrote:

Patrik,

Top work! It works really nicely on my camera. If I enter "cat
/proc/pwc/0/button" at the shell, it returns 0. If I push the button
then send the command again I get 1. I send the command again and I
get 0 again. Perfect!

One (small?) problem - the decompression on the camera no longer works
- I can only access non-compressed streams - everything else comes up
grey. Something to do with the error message I received below when
compiling, I suspect. Any ideas?

bash-3.00# make
make -C /lib/modules/2.6.12/build SUBDIRS=/home/andy/pwc modules
make[1]: Entering directory `/usr/src/linux-2.6.12'
CC [M]  /home/andy/pwc/pwc-if.o
CC [M]  /home/andy/pwc/pwc-misc.o
CC [M]  /home/andy/pwc/pwc-ctrl.o
CC [M]  /home/andy/pwc/pwc-uncompress.o
/home/andy/pwc/pwc-uncompress.c: In function `pwc_decompress':
/home/andy/pwc/pwc-uncompress.c:140: warning: unreachable code at
beginning of switch statement
CC [M]  /home/andy/pwc/pwc-timon.o
CC [M]  /home/andy/pwc/pwc-kiara.o
LD [M]  /home/andy/pwc/pwc.o
Building modules, stage 2.
MODPOST
CC      /home/andy/pwc/pwc.mod.o
LD [M]  /home/andy/pwc/pwc.ko
make[1]: Leaving directory `/usr/src/linux-2.6.12'

I might just amend my application so that it doesn't need to use
compressed streams - I didn't realise until today how much better
quality the uncompressed images were.

Let me know your Paypal address!

Cheers,

Andrew.

On 7/23/05, Patrik Jakobsson <> wrote:


Ok, now I've gotten it to work the way you described. In the /proc
filesystem you will find "pwc/minor#/button". The file contains a '1'
when the button has been pressed and otherwise '0'. The driver is only
reporting the status of the button when the device is open.
Download the full source at
http://www.shell.linux.se/xpatrikx/files/pwc-patched-with-snapshot-20050723.tar.bz2
or the patch at
http://www.shell.linux.se/xpatrikx/patches/pwc-snapshot-button-patch

Please tell me what you think, hopefully there are no nasty bugs in it
but use are your own risk :)

--Patrik Jakobsson

Andrew Cavers wrote:



Patrik,

Yes - I plan to use the button to invoke a callibration function and
the device will be open at the time. I really hope you can come up
with a workable solution to this one!

Look forward to hearing of any progress!

Andrew.

On 7/22/05, Patrik Jakobsson <> wrote:




Hi again,
I've gotten the snapshot button to work with my PCVC840K (type 740)
webcam. The button status data is embedded in the frames recieved from
the camera so you can only get the button status when the device is
open. There seems to be an option implemented in the driver to open the
device in "snapshot mode". Im not sure how this works so I need to look
some more at the driver. You wanted to use the button for invoking a
calibration function right? Is this when the device is opened or closed?

Andrew Cavers wrote:





Patrik,

You're right - I believe the Quickcam 4000 is a type 740. Do you know
why that code is only available to type 730 cameras?

I would really like to gain access to the button on my camera. As i'm
no programmer myself, I'd be willing to contribute by offering a small
bounty ($40/€30/£20 payable by Paypal?) to somebody who could
implement this code. An implementation similar to that on the driver
for ov511 cameras would be ideal - ie. the value of
/proc/video/ov511/<minor#>/button changes from 0 to 1 when the button
is pressed, and reverts to 0 when the file has been read.

Andrew.

On 7/21/05, Patrik Jakobsson <> wrote:






Hi Andrew,
I might be wrong but... you seem to have a type 740 camera and that
piece of code is only available to 730 cameras.

 --Patrik Jakobsson















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