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diff --git a/Documentation/DocBook/dvb/intro.xml b/Documentation/DocBook/dvb/intro.xml new file mode 100644 index 000000000000..0dc83f672ea2 --- /dev/null +++ b/Documentation/DocBook/dvb/intro.xml @@ -0,0 +1,191 @@ +<title>Introduction</title> + +<section id="requisites"> +<title>What you need to know</title> + +<para>The reader of this document is required to have some knowledge in +the area of digital video broadcasting (DVB) 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.</para> + +<para>Various DVB standards documents are available from +<ulink url="http://www.dvb.org" /> and/or +<ulink url="http://www.etsi.org" />.</para> + +<para>It is also necessary to know how to access unix/linux devices and +how to use ioctl calls. This also includes the knowledge of C or C++. +</para> +</section> + +<section id="history"> +<title>History</title> + +<para>The first API for DVB 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 DVB cards and their new features like recording MPEG streams +and filtering several section and PES data streams at the same time. +</para> + +<para>In early 2000, we were approached by Nokia with a proposal for a +new standard Linux DVB 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 +<ulink url="http://www.linuxtv.org/" /> in September 2000. +Convergence is the maintainer of the Linux DVB API. Together with the +LinuxTV community (i.e. you, the reader of this document), the Linux DVB +API will be constantly reviewed and improved. With the Linux driver for +the Siemens/Hauppauge DVB PCI card Convergence provides a first +implementation of the Linux DVB API.</para> +</section> + +<section id="overview"> +<title>Overview</title> + +<figure id="stb_components"> +<title>Components of a DVB card/STB</title> +<mediaobject> +<imageobject> +<imagedata fileref="dvbstb.pdf" format="PS" /> +</imageobject> +<imageobject> +<imagedata fileref="dvbstb.png" format="PNG" /> +</imageobject> +</mediaobject> +</figure> + +<para>A DVB PCI card or DVB set-top-box (STB) usually consists of the +following main hardware components: </para> + +<itemizedlist> + <listitem> + +<para>Frontend consisting of tuner and DVB demodulator</para> + +<para>Here the raw signal reaches the DVB 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.</para> + +</listitem> + <listitem> + +<para>Conditional Access (CA) hardware like CI adapters and smartcard slots +</para> + +<para>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.</para> + +</listitem> + <listitem> + <para>Demultiplexer which filters the incoming DVB stream</para> + +<para>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.</para> + +</listitem> +<listitem> + +<para>MPEG2 audio and video decoder</para> + +<para>The main targets of the demultiplexer are the MPEG2 audio and +video decoders. After decoding they pass on the uncompressed audio and +video to the computer screen or (through a PAL/NTSC encoder) to a TV +set.</para> + + +</listitem> +</itemizedlist> + +<para><xref linkend="stb_components" /> shows a crude schematic of the control and data flow +between those components.</para> + +<para>On a DVB PCI card not all of these have to be present since some +functionality can be provided by the main CPU of the PC (e.g. MPEG +picture and sound decoding) or is not needed (e.g. for data-only uses +like “internet over satellite”). Also not every card or STB +provides conditional access hardware.</para> + +</section> + +<section id="dvb_devices"> +<title>Linux DVB Devices</title> + +<para>The Linux DVB 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 DVB 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.</para> + +<para>All devices can be found in the <emphasis role="tt">/dev</emphasis> +tree under <emphasis role="tt">/dev/dvb</emphasis>. The individual devices +are called:</para> + +<itemizedlist> +<listitem> + +<para><emphasis role="tt">/dev/dvb/adapterN/audioM</emphasis>,</para> +</listitem> +<listitem> +<para><emphasis role="tt">/dev/dvb/adapterN/videoM</emphasis>,</para> +</listitem> +<listitem> +<para><emphasis role="tt">/dev/dvb/adapterN/frontendM</emphasis>,</para> +</listitem> + <listitem> + +<para><emphasis role="tt">/dev/dvb/adapterN/netM</emphasis>,</para> +</listitem> + <listitem> + +<para><emphasis role="tt">/dev/dvb/adapterN/demuxM</emphasis>,</para> +</listitem> + <listitem> + +<para><emphasis role="tt">/dev/dvb/adapterN/caM</emphasis>,</para></listitem></itemizedlist> + +<para>where N enumerates the DVB PCI 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 “<emphasis +role="tt">/dev/dvb/adapterN/</emphasis>” in the further dicussion +of these devices. The naming scheme for the devices is the same wheter +devfs is used or not.</para> + +<para>More details about the data structures and function calls of all +the devices are described in the following chapters.</para> + +</section> + +<section id="include_files"> +<title>API include files</title> + +<para>For each of the DVB devices a corresponding include file exists. +The DVB API include files should be included in application sources with +a partial path like:</para> + + +<programlisting> + #include <linux/dvb/frontend.h> +</programlisting> + +<para>To enable applications to support different API version, an +additional include file <emphasis +role="tt">linux/dvb/version.h</emphasis> exists, which defines the +constant <emphasis role="tt">DVB_API_VERSION</emphasis>. This document +describes <emphasis role="tt">DVB_API_VERSION 3</emphasis>. +</para> + +</section> + |