97. Adjusting webcam sensitivity/brightness on linux

The past year I've had problems with web cams on debian -- some of them look fine, some are way too dark, but either way, I had no good method of adjusting any of the settings. Cheese could be used for some settings, but it's not enough.

Yesterday I was greeted with this image:

While I could probably let in a bit more light in my office, it's still on the dark side...

There are command line tools for adjusting v4l devices (e.g. v4l-conf), but in this particular case a GUI tool would come in handy -- v4l2ucp. It can be installed from the standard debian repos.

Auto Gain can't be turned off for the zc3xx driver. Turns out that the "Light frequency filter" was set to no flicker by default. Changing it to 50 or 60 Hz lead to the image below:

The number of settings you can change depends on your driver --  below is the v4l2ucp window for an integrated thinkpad webcam:

96. Building a real-time kernel (3.2.9) on debian testing

Building an RT kernel is not terribly different from building a vanilla kernel:http://verahill.blogspot.com.au/2012/03/debian-testing-kernel-329.html

The main differences are:
1. the application of the relevant RT kernel patch
2. the configuration of RT specific kernel options

The latter step requires reading up on what an RT kernel does differently from a vanilla kernel, and the configuration will depend on your application.

The value of this guide is fairly small, since you wouldn't typically use an RT kernel on a desktop, but on a dedicate server or embedded system. I'm still working on a cross-compiling guide for non-x86 architectures.

In addition, having an RT kernel is only the first step -- it needs to be used in the correct way to allow for prioritising processes/pre-emptive execution in an efficient way. An overview for a particular application is given here: http://wiki.linuxmusicians.com/doku.php?id=system_configuration

Briefly,
sudo apt-get install kernel-package fakeroot
wget http://www.kernel.org/pub/linux/kernel/v3.0/linux-3.2.9.tar.bz2
wget http://kernel.org/pub/linux/kernel/projects/rt/3.2/patches-3.2.9-rt17.tar.bz2
tar -xvf linux-3.2.9.tar.bz2
cd linux-3.2.9/
bzcat ../patches-3.2.9-rt17.tar.bz2 |patch -p1
cat /boot/config-`uname -r` .config
make oldconfig

You get to answer a number of questions relating to real-time OS execution

  1. No Forced Preemption (Server) (PREEMPT_NONE)
> 2. Voluntary Kernel Preemption (Desktop) (PREEMPT_VOLUNTARY)
  3. Preemptible Kernel (Low-Latency Desktop) (PREEMPT__LL) (NEW)
  4. Preemptible Kernel (Basic RT) (PREEMPT_RTB) (NEW)
  5. Fully Preemptible Kernel (RT) (PREEMPT_RT_FULL) (NEW)
choice[1-5]: 4
[..]
 Testing module to detect hardware-induced latencies (HWLAT_DETECTOR) [M/n/y/?] (NEW)
[..]

Launch the build process
fakeroot make-kpkg -j7 --initrd --revision=3.2.9 --append-to-version=rt kernel_image kernel_headers 

where 7 is the number of cpu cores+1.

The deb-packages will be found in the folder above linux-3.2.9/ and can be installed using sudo pkg -i
.

97. Wine 1.4 out now -- very brief build instructions

UPDATE 16 May 2013: See here for Wine 1.5.30: http://verahill.blogspot.com.au/2013/05/416-wine-1530-in-chroot.html

UPDATE (10th Jan 2013): See here for Wine 1.5.21 using the multiarch approach in Debian Testing/Wheezy: http://verahill.blogspot.com.au/2013/01/308-compiling-wine-1521-on-debian.html

Updated list of dependencies for debian stable/squeeze: http://verahill.blogspot.com.au/2012/11/compiling-wine-155-from-source-using.html

The instructions are identical to those for wine1.4 rc4 and 5: http://verahill.blogspot.com.au/2012/02/debian-testing-wheezy-64-compiling-wine.html and wine 1.3.35: http://verahill.blogspot.com.au/2012/01/debian-testingwheezy-64-bit-installing.html

I've tested the build on 8 March 2012.

-- START HERE --
sudo apt-get install bison flex gcc libc6-dev libfontconfig-dev libfreetype6-dev libglu-dev libgsm1-dev libice-dev libjpeg-dev libldap-dev libmpg123-dev libncurses5-dev libopenal-dev libpng-dev libsm-dev libssl-dev libusb-dev libx11-dev libxcomposite-dev libxcursor-dev libxext-dev libxi-dev libxinerama-dev libxml2-dev libxrandr-dev libxrender-dev libxslt-dev libxt-dev libxxf86vm-dev make libcapi20-dev liblcms-dev libsane-dev libhal-dev libdbus-1-dev valgrind prelink libcups2-dev opencl-dev lib32opencl1 oss4-dev gettext lib32v4l-dev lib32ncurses5-dev lib32asound2-dev lib32z-dev ia32-libs-dev
mkdir ~/tmp
cd tmp/
wget http://prdownloads.sourceforge.net/wine/wine-1.4.tar.bz2
tar -xvf wine-1.4.tar.bz2
./configure

configure: gstreamer-0.10 base plugins 32-bit development files not found, gstreamer support disabled
configure: libgsm 32-bit development files not found, gsm 06.10 codec won't be supported.
configure: libtiff 32-bit development files not found, TIFF won't be supported.
configure: WARNING: libjpeg 32-bit development files not found, JPEG won't be supported.
configure: Finished.  Do 'make' to compile Wine.

The warnings about lack of support can safely be ignored if you don't need it. The TIFF error seems a bit random since it appears on some of my systems, but not others. I haven't figured out the responsible package yet.

make

sudo checkinstall --install=no

to build 23Mb deb package without installing it

 OR 

sudo make install

to install without building a package.

---

Note:
JPEG support is supposedly available if you

1. remove symlinks
sudo rm /usr/lib32/libjpeg.so.62 /usr/lib32/libjpeg.so.62.0.0
2. Then, create new ones
sudo ln -s /usr/lib32/libjpeg.so.8 /usr/lib32/libjpeg.so.62
sudo ln -s /usr/lib32/libjpeg.so.8 /usr/lib32/libjpeg.so.62.0.0

---

Edit:
I didn't know it before, but there's a slightly different, wine-specific, way of building described here http://chrisjrob.com/2012/03/08/wine-1-4-on-debian-wheezy/

To see you wine version do
winecfg

This is from a newer build - 1.5.6

---

Links to this page:
http://chrisjrob.com/2012/03/08/wine-1-4-on-debian-wheezy
http://forums.linuxmint.com/viewtopic.php?p=535245
http://debian.linux.pl/threads/26515-Instalacja-wine-1-4-w-Debianie-Squeeze