Documentation/userspace-api/media/dvb/intro.rst - linux - Git at Google

 .. 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``.
	.. 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``.