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Old 11-27-2008, 10:22 PM
Moritz Muehlenhoff
Default Bug#376999: linux-image-2.6.16-2-686: 'ov511' module seems to lack compression.

tags 376999 wishlist
tags 376999 wontfix

On Wed, Jul 05, 2006 at 11:56:40PM -0400, A. Costa wrote:
> Package: linux-image-2.6.16-2-686
> Version: 2.6.16-15
> Severity: normal
> I'm testing this webcam:
> % lsusb | grep -i cam
> Bus 001 Device 003: ID 05a9:0518 OmniVision Technologies, Inc. OV518 WebCam
> ...which the kernel loads a module for, yet can't seem to use:
> % dmesg | tail
> drivers/usb/media/ov511.c: USB OV518 video device found
> drivers/usb/media/ov511.c: Device revision 1
> drivers/usb/media/ov511.c: Sensor is an OV6630
> drivers/usb/media/ov511.c: Device at usb-0000:00:07.2-2 registered to minor 0
> usbcore: registered new driver ov511
> drivers/usb/media/ov511.c: v1.64 for Linux 2.5 : ov511 USB Camera Driver
> drivers/usb/media/ov511.c: No decompressor available
> drivers/usb/media/ov511.c: No decompressor available
> drivers/usb/media/ov511.c: No decompressor available
> drivers/usb/media/ov511.c: No decompressor available
> A Google search shows at least one other debian user is vexed by this
> bug:
> Troubles with Creative Webcam
> http://lists.debian.org/debian-user/2005/02/msg01010.html
> There's also another debian package 'ov511-source', but I was unable to
> get it to work with 'linux-image-2.6.16-2-686'.
> On the upstream 'ov511' page:
> http://alpha.dyndns.org/ov511/install.html
> ...it says:
> <snip>
> Using Compression Support:
> This information is only valid for the stable driver
> series (1.xx). With 2.xx drivers, compression is already
> built into ov511.o. For more information, please see the
> README that comes with the driver.
> Compression support will give you better frame rates with
> OV511 cameras, and is REQUIRED with OV518 cameras. It
> requires lots of CPU power, and reduces the image quality
> somewhat, though. If you want/need it, do the following:
> (NOTE: for OV518 cameras, substitute ov518_decomp for
> ov511_decomp )
> 1. Make sure you installed the latest driver using the
> above instructions. The driver that comes with kernels
> and operating systems by default has no compression
> support.
> 2. Add the following line to your /etc/modules.conf .
> This will load the decompressor after ov511 is loaded,
> and unload the decompressor before ov511 is unloaded:
> above ov511 ov511_decomp
> 3. If you want compression enabled by default all of the
> time, add the following line to /etc/modules.conf:
> options ov511 compress=1
> 4. Load ov511.If you didn't make compression the default
> in /etc/modules.conf , load it with the compress=1
> option (modprobe ov511 compress=1). If it is already
> loaded, remove it first with " rmmod ov511"
> 5. When you unload ov511, you must do it with modprobe
> (modprobe -r ov511). With rmmod, you will get "ov511:
> Device or resource busy", since it doesn't remove
> ov511_decomp automatically.
> <snip>
> ...it looks like there should be another module called 'ov511_decomp',
> but is currently missing from 'linux-image-2.6.16-2-686'. Maybe this
> 'ov511_decomp' module can be added?

The ov511 driver with the compression feature is available in the archive
in the ov51x-jpeg-source package, but intentionally not merged into
the Linux kernel by it's author:

http://www.rastageeks.org/ov51x-jpeg/index.php/Main_Page :
| ov51x-jpeg hacked was made because the original driver did not provide
| the jpeg decompression and current v4l implementation did not provide
| such facilities.
| To be clear, JPEG decompression should be considered 'evil' inside the
| kernel, and the normal way is to handle it in userland, so the original
| author was right doing what he did.


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