[media] DocBook: Improve DVB frontend description

<title>DVB Frontend API</title>

<para>The DVB frontend device controls the tuner and DVB demodulator

hardware. It can be accessed through <emphasis

role="bold">/dev/dvb/adapter0/frontend0</emphasis>. Data types and and

ioctl definitions can be accessed by including <emphasis

role="bold">linux/dvb/frontend.h</emphasis> in your application.</para>

<para>DVB frontends come in three varieties: DVB-S (satellite), DVB-C

(cable) and DVB-T (terrestrial). Transmission via the internet (DVB-IP)

is not yet handled by this API but a future extension is possible. For

DVB-S the frontend device also supports satellite equipment control

(SEC) via DiSEqC and V-SEC protocols. The DiSEqC (digital SEC)

specification is available from

<ulink url="http://www.eutelsat.com/satellites/4_5_5.html">Eutelsat</ulink>.</para>

<para>The DVB frontend API was designed to support three types of delivery systems:</para>

<itemizedlist>

    <listitem>Terrestrial systems: DVB-T, DVB-T2, ATSC, ATSC M/H, ISDB-T, DVB-H, DTMB, CMMB</listitem>

    <listitem>Cable systems: DVB-C Annex A/C, ClearQAM (DVB-C Annex B), ISDB-C</listitem>

    <listitem>Satellital systems: DVB-S, DVB-S2, DVB Turbo, ISDB-S, DSS</listitem>

</itemizedlist>

<para>The DVB frontend controls several sub-devices including:</para>

<itemizedlist>

    <listitem>Tuner</listitem>,

    <listitem>Digital TV demodulator</listitem>

    <listitem>Low noise amplifier (LNA)</listitem>

    <listitem>Satellite Equipment Control (SEC) hardware (only for Satellite).</listitem>

</itemizedlist>

<para>The frontend can be accessed through

    <emphasis role="bold">/dev/dvb/adapter?/frontend?</emphasis>. Data types and

    ioctl definitions can be accessed by including

    <emphasis role="bold">linux/dvb/frontend.h</emphasis> in your application.

</para>

<para>Note that the DVB API may also be used for MPEG decoder-only PCI

cards, in which case there exists no frontend device.</para>

<para>NOTE: Transmission via the internet (DVB-IP)

    is not yet handled by this API but a future extension is possible.</para>

<para>On Satellital systems, the API support for the Satellite Equipment Control

    (SEC) allows to power control and to send/receive signals to control the

    antenna subsystem, selecting the polarization and choosing the Intermediate

    Frequency IF) of the Low Noise Block Converter Feed Horn (LNBf). It

    supports the DiSEqC and V-SEC protocols. The DiSEqC (digital SEC)

specification is available at

<ulink url="http://www.eutelsat.com/satellites/4_5_5.html">Eutelsat</ulink>.</para>

<section id="frontend_types">

<title>Frontend Data Types</title>

<section id="fe-type-t">

<title>Frontend type</title>

<para>For historical reasons, frontend types are named by the type of modulation used in

transmission. The fontend types are given by fe_type_t type, defined as:</para>

<para>For historical reasons, frontend types are named by the type of modulation

    used in transmission. The fontend types are given by fe_type_t type, defined as:</para>

<table pgwide="1" frame="none" id="fe-type">

<title>Frontend types</title>