[{"id":30852,"web_url":"https://patchwork.libcamera.org/comment/30852/","msgid":"<20240816011608.GC15356@pendragon.ideasonboard.com>","date":"2024-08-16T01:16:08","subject":"Re: [PATCH v2 5/7] Documentation: Remove camera stack from\n\tintroduction.rst","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Dan,\n\nThank you for the patch.\n\nOn Thu, Aug 15, 2024 at 09:29:42AM +0100, Daniel Scally wrote:\n> The Camera Stack section of the introduction is largely a duplicate\n> of the section broken out from docs.rst. Remove it from the\n> introduction.rst file and consolidate anything that wasn't duplicated\n> into camera_stack.rst.\n> \n> Signed-off-by: Daniel Scally \n\nReviewed-by: Laurent Pinchart \n\n> ---\n> Changes since v1:\n> \n> \t- None\n> \n> Documentation/camera_stack.rst | 31 +++++++\n> Documentation/guides/introduction.rst | 112 +-------------------------\n> 2 files changed, 33 insertions(+), 110 deletions(-)\n> \n> diff --git a/Documentation/camera_stack.rst b/Documentation/camera_stack.rst\n> index 381385cb..6045ed91 100644\n> --- a/Documentation/camera_stack.rst\n> +++ b/Documentation/camera_stack.rst\n> @@ -76,3 +76,34 @@ The camera stack comprises four software layers. From bottom to top:\n> * The applications and upper level frameworks are based on the\n> libcamera framework or libcamera adaptation, and are outside of\n> the scope of the libcamera project.\n> +\n> +V4L2 Compatibility Layer\n> + V4L2 compatibility is achieved through a shared library that traps all\n> + accesses to camera devices and routes them to libcamera to emulate high-level\n> + V4L2 camera devices. It is injected in a process address space through\n> + ``LD_PRELOAD`` and is completely transparent for applications.\n> +\n> + The compatibility layer exposes camera device features on a best-effort basis,\n> + and aims for the level of features traditionally available from a UVC camera\n> + designed for video conferencing.\n> +\n> +Android Camera HAL\n> + Camera support for Android is achieved through a generic Android camera HAL\n> + implementation on top of libcamera. The HAL implements features required by\n> + Android and out of scope from libcamera, such as JPEG encoding support.\n> +\n> + This component is used to provide support for ChromeOS platforms\n> +\n> +GStreamer element (gstlibcamerasrc)\n> + A `GStreamer element`_ is provided to allow capture from libcamera supported\n> + devices through GStreamer pipelines, and connect to other elements for further\n> + processing.\n> +\n> + Development of this element is ongoing and is limited to a single stream.\n> +\n> +Native libcamera API\n> + Applications can make use of the libcamera API directly using the C++\n> + API. An example application and walkthrough using the libcamera API can be\n> + followed in the :doc:`Application writer's guide `\n> +\n> +.. _GStreamer element: https://gstreamer.freedesktop.org/documentation/application-development/basics/elements.html\n> diff --git a/Documentation/guides/introduction.rst b/Documentation/guides/introduction.rst\n> index 1898d5fe..e419eb9d 100644\n> --- a/Documentation/guides/introduction.rst\n> +++ b/Documentation/guides/introduction.rst\n> @@ -26,10 +26,8 @@ desirable results from the camera.\n> .. _Media Controller: https://www.linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/mediactl/media-controller.html\n> \n> \n> -In this developers guide, we will explore the `Camera Stack`_ and how it is\n> -can be visualised at a high level. The current `Platform Support`_ is\n> -detailed, as well as an overview of the `Licensing`_ requirements of the\n> -project.\n> +In this developers guide the current `Platform Support`_ is detailed, as well as\n> +an overview of the `Licensing`_ requirements of the project.\n> \n> This introduction is followed by a walkthrough tutorial to newcomers wishing to\n> support a new platform with the `Pipeline Handler Writers Guide`_ and for those\n> @@ -41,112 +39,6 @@ provides a tutorial of the key APIs exposed by libcamera.\n> \n> .. TODO: Correctly link to the other articles of the guide\n> \n> -Camera Stack\n> -------------\n> -\n> -The libcamera library is implemented in userspace, and makes use of underlying\n> -kernel drivers that directly interact with hardware.\n> -\n> -Applications can make use of libcamera through the native `libcamera API`_'s or\n> -through an adaptation layer integrating libcamera into a larger framework.\n> -\n> -.. _libcamera API: https://www.libcamera.org/api-html/index.html\n> -\n> -::\n> -\n> - Application Layer\n> - / +--------------+ +--------------+ +--------------+ +--------------+\n> - | | Native | | Framework | | Native | | Android |\n> - | | V4L2 | | Application | | libcamera | | Camera |\n> - | | Application | | (gstreamer) | | Application | | Framework |\n> - \\ +--------------+ +--------------+ +--------------+ +--------------+\n> -\n> - ^ ^ ^ ^\n> - | | | |\n> - | | | |\n> - v v | v\n> - Adaptation Layer |\n> - / +--------------+ +--------------+ | +--------------+\n> - | | V4L2 | | gstreamer | | | Android |\n> - | | Compatibility| | element | | | Camera |\n> - | | (preload) | |(libcamerasrc)| | | HAL |\n> - \\ +--------------+ +--------------+ | +--------------+\n> - |\n> - ^ ^ | ^\n> - | | | |\n> - | | | |\n> - v v v v\n> - libcamera Framework\n> - / +--------------------------------------------------------------------+\n> - | | |\n> - | | libcamera |\n> - | | |\n> - \\ +--------------------------------------------------------------------+\n> -\n> - ^ ^ ^\n> - Userspace | | |\n> - --------------------- | ---------------- | ---------------- | ---------------\n> - Kernel | | |\n> - v v v\n> -\n> - +-----------+ +-----------+ +-----------+\n> - | Media | <--> | Video | <--> | V4L2 |\n> - | Device | | Device | | Subdev |\n> - +-----------+ +-----------+ +-----------+\n> -\n> -The camera stack comprises of four software layers. From bottom to top:\n> -\n> -* The kernel drivers control the camera hardware and expose a low-level\n> - interface to userspace through the Linux kernel V4L2 family of APIs\n> - (Media Controller API, V4L2 Video Device API and V4L2 Subdev API).\n> -\n> -* The libcamera framework is the core part of the stack. It handles all control\n> - of the camera devices in its core component, libcamera, and exposes a native\n> - C++ API to upper layers.\n> -\n> -* The libcamera adaptation layer is an umbrella term designating the components\n> - that interface to libcamera in other frameworks. Notable examples are the V4L2\n> - compatibility layer, the gstreamer libcamera element, and the Android camera\n> - HAL implementation based on libcamera which are provided as a part of the\n> - libcamera project.\n> -\n> -* The applications and upper level frameworks are based on the libcamera\n> - framework or libcamera adaptation, and are outside of the scope of the\n> - libcamera project, however example native applications (cam, qcam) are\n> - provided for testing.\n> -\n> -\n> -V4L2 Compatibility Layer\n> - V4L2 compatibility is achieved through a shared library that traps all\n> - accesses to camera devices and routes them to libcamera to emulate high-level\n> - V4L2 camera devices. It is injected in a process address space through\n> - ``LD_PRELOAD`` and is completely transparent for applications.\n> -\n> - The compatibility layer exposes camera device features on a best-effort basis,\n> - and aims for the level of features traditionally available from a UVC camera\n> - designed for video conferencing.\n> -\n> -Android Camera HAL\n> - Camera support for Android is achieved through a generic Android camera HAL\n> - implementation on top of libcamera. The HAL implements features required by\n> - Android and out of scope from libcamera, such as JPEG encoding support.\n> -\n> - This component is used to provide support for ChromeOS platforms\n> -\n> -GStreamer element (gstlibcamerasrc)\n> - A `GStreamer element`_ is provided to allow capture from libcamera supported\n> - devices through GStreamer pipelines, and connect to other elements for further\n> - processing.\n> -\n> - Development of this element is ongoing and is limited to a single stream.\n> -\n> -Native libcamera API\n> - Applications can make use of the libcamera API directly using the C++\n> - API. An example application and walkthrough using the libcamera API can be\n> - followed in the `Application Writers Guide`_\n> -\n> -.. _GStreamer element: https://gstreamer.freedesktop.org/documentation/application-development/basics/elements.html\n> -\n> Platform Support\n> ----------------\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 8A206BDB13\n\tfor ;\n\tFri, 16 Aug 2024 01:16:37 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 6A6D5633B3;\n\tFri, 16 Aug 2024 03:16:36 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 0410E63369\n\tfor ;\n\tFri, 16 Aug 2024 03:16:34 +0200 (CEST)","from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi\n\t[81.175.209.231])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id E72586A6;\n\tFri, 16 Aug 2024 03:15:35 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"qjtONMry\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1723770936;\n\tbh=K2Z1ohiqlw19KmZqM+LyxzuRme59Kt1jk82J5UsgNIs=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=qjtONMryy/FFKbZXoAD6jv+Dbki3qFbR5MgbP/6c/D5qcCWmiDpfHo+3Ji5FvTowM\n\tAAIFm5A9Vp+QDpOEHTFq23mlG9nXFuRVxQdnWMy7NA5qrzdUlzyuz+NaCnFhRHtvks\n\tS1TzhyRcnJzjUFnsEy0VXu7UpWZUSoCqsFzQnTjY=","Date":"Fri, 16 Aug 2024 04:16:08 +0300","From":"Laurent Pinchart ","To":"Daniel Scally ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v2 5/7] Documentation: Remove camera stack from\n\tintroduction.rst","Message-ID":"<20240816011608.GC15356@pendragon.ideasonboard.com>","References":"<20240815082944.170109-1-dan.scally@ideasonboard.com>\n\t<20240815082944.170109-6-dan.scally@ideasonboard.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20240815082944.170109-6-dan.scally@ideasonboard.com>","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]