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The usage of # in embedded URIs for references to sections in reStructuredText is HTML specific. Use the standard rST reference to targets instead, to be compatible with other formats as well, should this documentation ever be exported to PDF, for example. See [1] for an equivalent commit in the Linux Kernel documentation. [1] https://lore.kernel.org/linux-doc/20201228144537.135353-1-nfraprado@protonmail.com/ Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com> Reviewed-by: Sebastian Fricke <sebastian.fricke@posteo.net> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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.. SPDX-License-Identifier: CC-BY-SA-4.0
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Environment variables
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=====================
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The libcamera behaviour can be tuned through environment variables. This
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document lists all the available variables and describes their usage.
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List of variables
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-----------------
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LIBCAMERA_LOG_FILE
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The custom destination for log output.
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Example value: ``/home/{user}/camera_log.log``
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LIBCAMERA_LOG_LEVELS
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Configure the verbosity of log messages for different categories (`more <Log levels_>`__).
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Example value: ``*:DEBUG``
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LIBCAMERA_IPA_CONFIG_PATH
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Define custom search locations for IPA configurations (`more <IPA configuration_>`__).
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Example value: ``${HOME}/.libcamera/share/ipa:/opt/libcamera/vendor/share/ipa``
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LIBCAMERA_IPA_MODULE_PATH
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Define custom search locations for IPA modules (`more <IPA module_>`__).
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Example value: ``${HOME}/.libcamera/lib:/opt/libcamera/vendor/lib``
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Further details
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---------------
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Notes about debugging
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~~~~~~~~~~~~~~~~~~~~~
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The environment variables ``LIBCAMERA_LOG_FILE`` and ``LIBCAMERA_LOG_LEVELS``
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are used to modify the destination and verbosity of messages provided by
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libcamera.
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The ``LIBCAMERA_LOG_LEVELS`` variable accepts a comma-separated list of
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'category:level' pairs.
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The `level <Log levels_>`__ part is mandatory and can either be specified by
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name or by numerical index associated with each level.
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The optional `category <Log categories_>`__ is a string matching the categories
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defined by each file in the source base using the logging infrastructure. It
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can include a wildcard ('*') character at the end to match multiple categories.
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For more information refer to the `API documentation <http://libcamera.org/api-html/log_8h.html#details>`__.
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Examples:
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Enable full debug output to a separate file, for every `category <Log categories_>`__
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within a local environment:
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.. code:: bash
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:~$ LIBCAMERA_LOG_FILE='/tmp/example_log.log' \
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LIBCAMERA_LOG_LEVELS=0 \
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cam --list
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Enable full debug output for the categories ``Camera`` and ``V4L2`` within a
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global environment:
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.. code:: bash
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:~$ export LIBCAMERA_LOG_LEVELS='Camera:DEBUG,V4L2:DEBUG'
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:~$ cam --list
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Log levels
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~~~~~~~~~~~
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This is the list of available log levels, notice that all levels below
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the chosen one are printed, while those above are discarded.
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- DEBUG (0)
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- INFO (1)
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- WARN (2)
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- ERROR (3)
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- FATAL (4)
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Example:
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If you choose WARN (2), you will be able to see WARN (2), ERROR (3) and FATAL (4)
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but not DEBUG (0) and INFO (1).
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Log categories
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~~~~~~~~~~~~~~~
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Every category represents a specific area of the libcamera codebase,
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the names can be located within the source code, for example:
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`src/libcamera/camera_manager.cpp <https://git.libcamera.org/libcamera/libcamera.git/tree/src/libcamera/camera_manager.cpp#n35>`__
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.. code:: cpp
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LOG_DEFINE_CATEGORY(Camera)
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There are two available macros used to assign a category name to a part of the
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libcamera codebase:
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LOG_DEFINE_CATEGORY
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This macro is required, in order to use the ``LOGC`` macro for a particular
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category. It can only be used once for each category. If you want to create
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log messages within multiple compilation units for the same category utilize
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the ``LOG_DECLARE_CATEGORY`` macro, in every file except the definition file.
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LOG_DECLARE_CATEGORY
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Used for sharing an already defined category between multiple separate
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compilation units.
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Both macros have to be used within the libcamera namespace of the C++ source
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code.
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IPA configuration
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~~~~~~~~~~~~~~~~~
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IPA modules use configuration files to store parameters. The format and
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contents of the configuration files is specific to the IPA module. They usually
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contain tuning parameters for the algorithms, in JSON format.
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The ``LIBCAMERA_IPA_CONFIG_PATH`` variable can be used to specify custom
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storage locations to search for those configuration files.
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`Examples <https://git.libcamera.org/libcamera/libcamera.git/tree/src/ipa/raspberrypi/data>`__
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IPA module
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~~~~~~~~~~~
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In order to locate the correct IPA module for your hardware, libcamera gathers
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existing IPA modules from multiple locations. The default locations for this
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operation are the installed system path (for example on Debian:
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``/usr/local/x86_64-pc-linux-gnu/libcamera``) and the build directory.
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With the ``LIBCAMERA_IPA_MODULE_PATH``, you can specify a non-default location
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to search for IPA modules.
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