9076e88fc3
Previously, since we acquired the libcamera camera upon open(), it was impossible to support multiple open, as any subsequent opens would return error because the camera would already be acquired. To fix this, we first initialize the camera in the first call to V4L2CameraProxy::open(), just to heat up the stream format cache. We then add ownership by a V4L2CameraFile of a V4L2Camera via the V4L2CameraProxy. All vidioc ioctls prior to reqbufs > 0 (except for s_fmt) are able to access the camera without ownership. A call to reqbufs > 0 (and s_fmt) will take ownership, and the ownership will be released at reqbufs = 0. While ownership is assigned, the eventfd that should be signaled (and cleared) by V4L2Camera and V4L2CameraProxy is set to the V4L2CameraFile that has ownership, and is cleared when the ownership is released. In case close() is called without a reqbufs = 0 first, the ownership is also released on close(). We also use the V4L2CameraFile to contain all the information specific to an open instance of the file. This removes the need to keep track of such information within V4L2CameraProxy via multiple maps from int fd to info. Since V4L2 does not expect reqbufs 0 to ever return error, make V4L2CameraProxy::freeBuffers() return void. Signed-off-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
.. 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}
for libcamera: [required]
meson (>= 0.47) ninja-build python3-yaml
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 device hotplug enumeration: [optional]
pkg-config libudev-dev
for documentation: [optional]
python3-sphinx doxygen
for gstreamer: [optional]
libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev
for IPA module signing: [required]
libgnutls28-dev openssl
for qcam: [optional]
qtbase5-dev libqt5core5a libqt5gui5 libqt5widgets5
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