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The ControlValue<T> constructor for non-array values is a template function that participates in overload resolution for all T types that are not Span or std::string. Other T types that are not supported then result in a compilation error. This causes issues when calling an overloaded function that can accept both a ControlValue and a Span with an std::array<U> parameter. The first overload will be resolved using implicit construction of a ControlValue from the std::array<U>, while the second overload will be resolved using implicit construction of a Span<U> from the std::array<U>. This results in a compilation error due to an ambiguous function call. The first overload is invalid, selecting it would result in a compilation error in the ControlValue constructor, as the ControlValue<T> constructor doesn't support std::array<U> for type T. The compiler can't know about that, as overload resolution happens earlier. To fix it, we can disable the ControlValue<T> constructor for unsupported types T, moving the type check from compilation of the function to overload resolution. The constructor will not participate in overload resolution, and the call won't be ambiguous. The end result is the same for unsupported types, compilation will fail. Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> |
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README.rst |
.. SPDX-License-Identifier: CC-BY-SA-4.0 .. section-begin-libcamera =========== libcamera =========== **A complex camera support library for Linux, Android, and ChromeOS** Cameras are complex devices that need heavy hardware image processing operations. Control of the processing is based on advanced algorithms that must run on a programmable processor. This has traditionally been implemented in a dedicated MCU in the camera, but in embedded devices algorithms have been moved to the main CPU to save cost. Blurring the boundary between camera devices and Linux often left the user with no other option than a vendor-specific closed-source solution. To address this problem the Linux media community has very recently started collaboration with the industry to develop a camera stack that will be open-source-friendly while still protecting vendor core IP. libcamera was born out of that collaboration and will offer modern camera support to Linux-based systems, including traditional Linux distributions, ChromeOS and Android. .. section-end-libcamera .. section-begin-getting-started Getting Started --------------- To fetch the sources, build and install: :: git clone git://linuxtv.org/libcamera.git cd libcamera meson build ninja -C build install Dependencies ~~~~~~~~~~~~ The following Debian/Ubuntu packages are required for building libcamera. Other distributions may have differing package names: A C++ toolchain: [required] Either {g++, clang} Meson Build system: [required] meson (>= 0.51) ninja-build pkg-config If your distribution doesn't provide a recent enough version of meson, you can install or upgrade it using pip3. .. code:: pip3 install --user meson pip3 install --user --upgrade meson for the libcamera core: [required] python3-yaml for IPA module signing: [required] libgnutls28-dev openssl for the Raspberry Pi IPA: [optional] libboost-dev Support for Raspberry Pi can be disabled through the meson 'pipelines' option to avoid this dependency. for device hotplug enumeration: [optional] libudev-dev for documentation: [optional] python3-sphinx doxygen graphviz for gstreamer: [optional] libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev for qcam: [optional] qtbase5-dev libqt5core5a libqt5gui5 libqt5widgets5 qttools5-dev-tools libtiff-dev Using GStreamer plugin ~~~~~~~~~~~~~~~~~~~~~~ To use GStreamer plugin from source tree, set the following environment so that GStreamer can find it. export GST_PLUGIN_PATH=$(pwd)/build/src/gstreamer The debugging tool `gst-launch-1.0` can be used to construct and pipeline and test it. The following pipeline will stream from the camera named "Camera 1" onto the default video display element on your system. .. code:: gst-launch-1.0 libcamerasrc camera-name="Camera 1" ! videoconvert ! autovideosink .. section-end-getting-started