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Re: [pwc] Problems with compression in pwc module (SOLUTION)

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Subject: Re: [pwc] Problems with compression in pwc module (SOLUTION)
From: Pablo Alvarado <>
Date: Mon, 30 Oct 2006 13:19:06 -0600
Hello,

I found the solution to my problem, which may be helpful for someone else:

Debian's package for the kernels include a pwc module in

/lib/modules/2.6.17-2-686/kernel/drivers/media/video/pwc/pwc.ko

but when you install the pwc using the module-assistant it creates it in
another path

/lib/modules/2.6.17-2-686/kernel/drivers/usb/media/pwc.ko

The module dependencies created with "depmod" select the first "obsolete"
module, which does not support compression.  Just remove that module and
create the dependencies again:

su
rm /lib/modules/2.6.17-2-686/kernel/drivers/media/video/pwc/pwc.ko
depmod
rmmod pwc
modprobe pwc

and voilà!  Everything works now as expected!

Regards,

Pablo


On Monday 30 October 2006 11:14, Pablo Alvarado wrote:
> Hello,
>
> I'm experiencing some weird problems with a ToUCam
> Camera (740) and the pwc kernel module, whenever I
> activate any compression level.  I can get the images
> and control the camera without any difficulties in all
> available uncompressed modes, but as soon as I
> activate the compression mode (any of the three
> available) I get a grey image with RGB values
> (128,128,128).
>
> I've tried several programs (camstream and LTI-Lib
> lti::toUCam functor) and all of them behave the same
> way.  I have debugged the LTI-Lib software and all
> ioctl calls return successfully when the compression
> parameters are set or the image is requested.  In some
> computers the kernel module with the mentioned
> software works fine (with compression and everything),
> but in some others I just get the grey image.  All
> computers have a kernel 2.6.17-2 and the pwc module
> version 10.0.12-rc1+final (installed with Debian's
> module-assistant), so I don't think it is a kernel
> compatibility problem.  It is not the camera because
> in all tests I used the same one.
>
> I though the grey images were generated by the
> software that used the API when it detected an error,
> but the grey image is directly provided by the API
> interface without reporting any errors.  The size of
> the returned grey images is correct.  The output in
> /var/log/syslog indicates nothing special:
>
> Oct 30 10:14:59 palvarado kernel: pwc
> set_video_mode(160x120 @ 30, palette
> 15).
> Oct 30 10:14:59 palvarado kernel: pwc decode_size = 1.
> Oct 30 10:14:59 palvarado kernel: pwc Using alternate
> setting 8.
> Oct 30 10:15:25 palvarado kernel: pwc
> set_video_mode(160x120 @ 30, palette
> 15).
> Oct 30 10:15:25 palvarado kernel: pwc decode_size = 1.
> Oct 30 10:15:25 palvarado kernel: pwc Using alternate
> setting 5.
>
> the first three lines were reported as the compression
> was deactivated (and a valid image was obtained), and
> the last three lines when the compression was
> activated an the image turned grey.
>
> Any hint would be very welcome,
>
> Regards,
>
> Pablo

--
Dr. Pablo Alvarado                      E-Mail: 
Escuela de Ingeniería Electrónica       Tel.:   (+506) 550 2106
Instituto Tecnológico de Costa Rica     Fax.:   (+506) 591 6629
Apartado Postal 159-7050
Cartago
Costa Rica
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