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Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _dvb_introdution:
+
+************
+Introduction
+************
+
+
+.. _requisites:
+
+What you need to know
+=====================
+
+The reader of this document is required to have some knowledge in the
+area of digital video broadcasting (Digital TV) and should be familiar with
+part I of the MPEG2 specification ISO/IEC 13818 (aka ITU-T H.222), i.e
+you should know what a program/transport stream (PS/TS) is and what is
+meant by a packetized elementary stream (PES) or an I-frame.
+
+Various Digital TV standards documents are available for download at:
+
+- European standards (DVB): http://www.dvb.org and/or http://www.etsi.org.
+- American standards (ATSC): https://www.atsc.org/standards/
+- Japanese standards (ISDB): http://www.dibeg.org/
+
+It is also necessary to know how to access Linux devices and how to
+use ioctl calls. This also includes the knowledge of C or C++.
+
+
+.. _history:
+
+History
+=======
+
+The first API for Digital TV cards we used at Convergence in late 1999 was an
+extension of the Video4Linux API which was primarily developed for frame
+grabber cards. As such it was not really well suited to be used for Digital
+TV cards and their new features like recording MPEG streams and filtering
+several section and PES data streams at the same time.
+
+In early 2000, Convergence was approached by Nokia with a proposal for a new
+standard Linux Digital TV API. As a commitment to the development of terminals
+based on open standards, Nokia and Convergence made it available to all
+Linux developers and published it on https://linuxtv.org in September
+2000. With the Linux driver for the Siemens/Hauppauge DVB PCI card,
+Convergence provided a first implementation of the Linux Digital TV API.
+Convergence was the maintainer of the Linux Digital TV API in the early
+days.
+
+Now, the API is maintained by the LinuxTV community (i.e. you, the reader
+of this document). The Linux  Digital TV API is constantly reviewed and
+improved together with the improvements at the subsystem's core at the
+Kernel.
+
+
+.. _overview:
+
+Overview
+========
+
+
+.. _stb_components:
+
+.. kernel-figure:: dvbstb.svg
+    :alt:   dvbstb.svg
+    :align: center
+
+    Components of a Digital TV card/STB
+
+A Digital TV card or set-top-box (STB) usually consists of the
+following main hardware components:
+
+Frontend consisting of tuner and digital TV demodulator
+   Here the raw signal reaches the digital TV hardware from a satellite dish or
+   antenna or directly from cable. The frontend down-converts and
+   demodulates this signal into an MPEG transport stream (TS). In case
+   of a satellite frontend, this includes a facility for satellite
+   equipment control (SEC), which allows control of LNB polarization,
+   multi feed switches or dish rotors.
+
+Conditional Access (CA) hardware like CI adapters and smartcard slots
+   The complete TS is passed through the CA hardware. Programs to which
+   the user has access (controlled by the smart card) are decoded in
+   real time and re-inserted into the TS.
+
+   .. note::
+
+      Not every digital TV hardware provides conditional access hardware.
+
+Demultiplexer which filters the incoming Digital TV MPEG-TS stream
+   The demultiplexer splits the TS into its components like audio and
+   video streams. Besides usually several of such audio and video
+   streams it also contains data streams with information about the
+   programs offered in this or other streams of the same provider.
+
+Audio and video decoder
+   The main targets of the demultiplexer are audio and video
+   decoders. After decoding, they pass on the uncompressed audio and
+   video to the computer screen or to a TV set.
+
+   .. note::
+
+      Modern hardware usually doesn't have a separate decoder hardware, as
+      such functionality can be provided by the main CPU, by the graphics
+      adapter of the system or by a signal processing hardware embedded on
+      a Systems on a Chip (SoC) integrated circuit.
+
+      It may also not be needed for certain usages (e.g. for data-only
+      uses like “internet over satellite”).
+
+:ref:`stb_components` shows a crude schematic of the control and data
+flow between those components.
+
+
+
+.. _dvb_devices:
+
+Linux Digital TV Devices
+========================
+
+The Linux Digital TV API lets you control these hardware components through
+currently six Unix-style character devices for video, audio, frontend,
+demux, CA and IP-over-DVB networking. The video and audio devices
+control the MPEG2 decoder hardware, the frontend device the tuner and
+the Digital TV demodulator. The demux device gives you control over the PES
+and section filters of the hardware. If the hardware does not support
+filtering these filters can be implemented in software. Finally, the CA
+device controls all the conditional access capabilities of the hardware.
+It can depend on the individual security requirements of the platform,
+if and how many of the CA functions are made available to the
+application through this device.
+
+All devices can be found in the ``/dev`` tree under ``/dev/dvb``. The
+individual devices are called:
+
+-  ``/dev/dvb/adapterN/audioM``,
+
+-  ``/dev/dvb/adapterN/videoM``,
+
+-  ``/dev/dvb/adapterN/frontendM``,
+
+-  ``/dev/dvb/adapterN/netM``,
+
+-  ``/dev/dvb/adapterN/demuxM``,
+
+-  ``/dev/dvb/adapterN/dvrM``,
+
+-  ``/dev/dvb/adapterN/caM``,
+
+where ``N`` enumerates the Digital TV cards in a system starting from 0, and
+``M`` enumerates the devices of each type within each adapter, starting
+from 0, too. We will omit the “``/dev/dvb/adapterN/``\ ” in the further
+discussion of these devices.
+
+More details about the data structures and function calls of all the
+devices are described in the following chapters.
+
+
+.. _include_files:
+
+API include files
+=================
+
+For each of the Digital TV devices a corresponding include file exists. The
+Digital TV API include files should be included in application sources with a
+partial path like:
+
+
+.. code-block:: c
+
+	#include <linux/dvb/ca.h>
+
+	#include <linux/dvb/dmx.h>
+
+	#include <linux/dvb/frontend.h>
+
+	#include <linux/dvb/net.h>
+
+
+To enable applications to support different API version, an additional
+include file ``linux/dvb/version.h`` exists, which defines the constant
+``DVB_API_VERSION``. This document describes ``DVB_API_VERSION 5.10``.