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uvcdynctrl - Manage dynamic controls in uvcvideo


For an introduction to dynamic controls you should first read the dynctrl.txt
that comes with the Linux UVC driver. You can find it here:


The combination of uvcdynctrl and libwebcam allows to manage these dynamic
controls from user space. While libwebcam contains the actual implementation,
uvcdynctrl presents a command line interface to do so.

Currently only the UVCIOC_CTRL_ADD and UVCIOC_CTRL_MAP ioctls are supported.
Support for the remaining functions is planned. The documentation is not really
complete at this time. In particular, the XML format that is used to describe
dynamic controls is undocumented except for a sample file and an XML schema.
This will be fixed very soon.

uvcdynctrl is designed to eventually work together with udev, so that control
mappings are automatically added whenever a UVC device is plugged and a
matching dynamic controls configuration file is available.

Apart from the dynamic controls feature uvcdynctrl also provides a few handy
functions that illustrate the power of libwebcam. Check out the built-in
command line help for details.

udev support

The uvcdynctrl package contains udev support, i.e. a udev rule file and a
helper script that calls uvcdynctrl to import the appropriate XML file when
a camera is connected.

If you run "make install" as root, the following udev-related files will be

  /etc/udev/rules.d/80-uvcdynctrl.rules (rule for V4L devices)
  /lib/udev/uvcdynctrl (helper script to launch uvcdynctrl)
  /etc/udev/data/046d/logitech.xml (dynamic control configuration for Logitech

These paths are hardcoded in uvcdynctrl/CMakeLists.txt and have only been
tested on Ubuntu with udev versions >= 141. If your distribution uses different
paths, you need to make changes to that file before running the installation.

If you're using an older version of udev you may want to try the udev scripts
of an older version which is tagged as "0.1.3-pre" and can be found here:

Please send us feedback (preferrably through the QuickCam Team forum, see the
main README file for the link) about the udev functionality, especially on
non-Ubuntu systems.

If you want to debug the uvcdynctrl udev script, you can find some basic debug
output in /var/log/uvcdynctrl-udev.log.

Change log

- Reorganized the directory layout and build system.
- Exit with a non-zero code if errors occur while getting or setting controls.
- Improved udev support (udev >= 141 is required now).

0.2 (2008-01-29): 
- Experimental support for udev (support script and rules).
- Added a new option -f or --formats to list a device's frame format list
  (pixel formats, frame sizes, and frame intervals).
- Make use of the improved error message reporting in libwebcam.
- Added support for displaying processing statistics in verbose mode.
- Support for the new informational messages (dynctrl).
- Added a hint to the quick help on how to set negative control values.
- Fix: Import (-i) no longer needs a valid device to be specified (or the
  default video0 to be present).

0.1: Initial release

Building, questions, and feedback

Please see the README file in the top level directory for building
instructions and how to contact the developers.

Copyright and license

Copyright (c) 2006-2010 Logitech.

uvcdynctrl is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

uvcdynctrl is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with uvcdynctrl.  If not, see <http://www.gnu.org/licenses/>.