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Diffstat (limited to 'Documentation/guides/introduction.rst')
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1 files changed, 1 insertions, 108 deletions
diff --git a/Documentation/guides/introduction.rst b/Documentation/guides/introduction.rst index 8368bd4a..d1e67654 100644 --- a/Documentation/guides/introduction.rst +++ b/Documentation/guides/introduction.rst @@ -26,8 +26,7 @@ desirable results from the camera. .. _Media Controller: https://www.linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/mediactl/media-controller.html -In this developers guide, we will explore the `Camera Stack`_ and how it is -can be visualised at a high level, and explore the internal `Architecture`_ of +In this developers guide, we will explore the internal `Architecture`_ of the libcamera library with its components. The current `Platform Support`_ is detailed, as well as an overview of the `Licensing`_ requirements of the project. @@ -42,112 +41,6 @@ provides a tutorial of the key APIs exposed by libcamera. .. TODO: Correctly link to the other articles of the guide -Camera Stack ------------- - -The libcamera library is implemented in userspace, and makes use of underlying -kernel drivers that directly interact with hardware. - -Applications can make use of libcamera through the native `libcamera API`_'s or -through an adaptation layer integrating libcamera into a larger framework. - -.. _libcamera API: https://www.libcamera.org/api-html/index.html - -:: - - Application Layer - / +--------------+ +--------------+ +--------------+ +--------------+ - | | Native | | Framework | | Native | | Android | - | | V4L2 | | Application | | libcamera | | Camera | - | | Application | | (gstreamer) | | Application | | Framework | - \ +--------------+ +--------------+ +--------------+ +--------------+ - - ^ ^ ^ ^ - | | | | - | | | | - v v | v - Adaptation Layer | - / +--------------+ +--------------+ | +--------------+ - | | V4L2 | | gstreamer | | | Android | - | | Compatibility| | element | | | Camera | - | | (preload) | |(libcamerasrc)| | | HAL | - \ +--------------+ +--------------+ | +--------------+ - | - ^ ^ | ^ - | | | | - | | | | - v v v v - libcamera Framework - / +--------------------------------------------------------------------+ - | | | - | | libcamera | - | | | - \ +--------------------------------------------------------------------+ - - ^ ^ ^ - Userspace | | | - --------------------- | ---------------- | ---------------- | --------------- - Kernel | | | - v v v - - +-----------+ +-----------+ +-----------+ - | Media | <--> | Video | <--> | V4L2 | - | Device | | Device | | Subdev | - +-----------+ +-----------+ +-----------+ - -The camera stack comprises of four software layers. From bottom to top: - -* The kernel drivers control the camera hardware and expose a low-level - interface to userspace through the Linux kernel V4L2 family of APIs - (Media Controller API, V4L2 Video Device API and V4L2 Subdev API). - -* The libcamera framework is the core part of the stack. It handles all control - of the camera devices in its core component, libcamera, and exposes a native - C++ API to upper layers. - -* The libcamera adaptation layer is an umbrella term designating the components - that interface to libcamera in other frameworks. Notable examples are the V4L2 - compatibility layer, the gstreamer libcamera element, and the Android camera - HAL implementation based on libcamera which are provided as a part of the - libcamera project. - -* The applications and upper level frameworks are based on the libcamera - framework or libcamera adaptation, and are outside of the scope of the - libcamera project, however example native applications (cam, qcam) are - provided for testing. - - -V4L2 Compatibility Layer - V4L2 compatibility is achieved through a shared library that traps all - accesses to camera devices and routes them to libcamera to emulate high-level - V4L2 camera devices. It is injected in a process address space through - ``LD_PRELOAD`` and is completely transparent for applications. - - The compatibility layer exposes camera device features on a best-effort basis, - and aims for the level of features traditionally available from a UVC camera - designed for video conferencing. - -Android Camera HAL - Camera support for Android is achieved through a generic Android camera HAL - implementation on top of libcamera. The HAL implements features required by - Android and out of scope from libcamera, such as JPEG encoding support. - - This component is used to provide support for ChromeOS platforms - -GStreamer element (gstlibcamerasrc) - A `GStreamer element`_ is provided to allow capture from libcamera supported - devices through GStreamer pipelines, and connect to other elements for further - processing. - - Development of this element is ongoing and is limited to a single stream. - -Native libcamera API - Applications can make use of the libcamera API directly using the C++ - API. An example application and walkthrough using the libcamera API can be - followed in the `Application Writers Guide`_ - -.. _GStreamer element: https://gstreamer.freedesktop.org/documentation/application-development/basics/elements.html - Architecture ------------ |