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<title>DVB Frontend API</title>
<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: 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="query-dvb-frontend-info">
<title>Querying frontend information</title>
<para>Usually, the first thing to do when the frontend is opened is to
check the frontend capabilities. This is done using <link linkend="FE_GET_INFO">FE_GET_INFO</link>. This ioctl will enumerate
the DVB API version and other characteristics about the frontend, and
can be opened either in read only or read/write mode.</para>
</section>
<section id="dvb-fe-read-status">
<title>Querying frontend status and statistics</title>
<para>Once <link linkend="FE_GET_PROPERTY"><constant>FE_SET_PROPERTY</constant></link>
is called, the frontend will run a kernel thread that will periodically
check for the tuner lock status and provide statistics about the quality
of the signal.</para>
<para>The information about the frontend tuner locking status can be queried
using <link linkend="FE_READ_STATUS">FE_READ_STATUS</link>.</para>
<para>Signal statistics are provided via <link linkend="FE_GET_PROPERTY"><constant>FE_GET_PROPERTY</constant></link>.
Please notice that several statistics require the demodulator to be fully
locked (e. g. with FE_HAS_LOCK bit set). See
<xref linkend="frontend-stat-properties">Frontend statistics indicators</xref>
for more details.</para>
</section>
&sub-dvbproperty;
<section>
<title>More OFDM parameters</title>
<section id="fe-hierarchy-t">
<title>frontend hierarchy</title>
<programlisting>
typedef enum fe_hierarchy {
HIERARCHY_NONE,
HIERARCHY_1,
HIERARCHY_2,
HIERARCHY_4,
HIERARCHY_AUTO
} fe_hierarchy_t;
</programlisting>
</section>
</section>
<section id="frontend_fcalls">
<title>Frontend Function Calls</title>
<section id="frontend_f_open">
<title>open()</title>
<para>DESCRIPTION</para>
<informaltable><tgroup cols="1"><tbody><row>
<entry align="char">
<para>This system call opens a named frontend device (/dev/dvb/adapter0/frontend0)
for subsequent use. Usually the first thing to do after a successful open is to
find out the frontend type with <link linkend="FE_GET_INFO">FE_GET_INFO</link>.</para>
<para>The device can be opened in read-only mode, which only allows monitoring of
device status and statistics, or read/write mode, which allows any kind of use
(e.g. performing tuning operations.)
</para>
<para>In a system with multiple front-ends, it is usually the case that multiple devices
cannot be open in read/write mode simultaneously. As long as a front-end
device is opened in read/write mode, other open() calls in read/write mode will
either fail or block, depending on whether non-blocking or blocking mode was
specified. A front-end device opened in blocking mode can later be put into
non-blocking mode (and vice versa) using the F_SETFL command of the fcntl
system call. This is a standard system call, documented in the Linux manual
page for fcntl. When an open() call has succeeded, the device will be ready
for use in the specified mode. This implies that the corresponding hardware is
powered up, and that other front-ends may have been powered down to make
that possible.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int open(const char ⋆deviceName, int flags);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>const char
*deviceName</para>
</entry><entry
align="char">
<para>Name of specific video device.</para>
</entry>
</row><row><entry
align="char">
<para>int flags</para>
</entry><entry
align="char">
<para>A bit-wise OR of the following flags:</para>
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>O_RDONLY read-only access</para>
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>O_RDWR read/write access</para>
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>O_NONBLOCK open in non-blocking mode</para>
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>(blocking mode is the default)</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURN VALUE</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>ENODEV</para>
</entry><entry
align="char">
<para>Device driver not loaded/available.</para>
</entry>
</row><row><entry
align="char">
<para>EINTERNAL</para>
</entry><entry
align="char">
<para>Internal error.</para>
</entry>
</row><row><entry
align="char">
<para>EBUSY</para>
</entry><entry
align="char">
<para>Device or resource busy.</para>
</entry>
</row><row><entry
align="char">
<para>EINVAL</para>
</entry><entry
align="char">
<para>Invalid argument.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="frontend_f_close">
<title>close()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This system call closes a previously opened front-end device. After closing
a front-end device, its corresponding hardware might be powered down
automatically.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int close(int fd);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURN VALUE</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid open file descriptor.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
&sub-fe-get-info;
&sub-fe-read-status;
&sub-fe-get-property;
&sub-fe-diseqc-reset-overload;
&sub-fe-diseqc-send-master-cmd;
&sub-fe-diseqc-recv-slave-reply;
&sub-fe-diseqc-send-burst;
&sub-fe-set-tone;
&sub-fe-set-voltage;
&sub-fe-enable-high-lnb-voltage;
&sub-fe-set-frontend-tune-mode;
</section>
<section id="frontend_legacy_dvbv3_api">
<title>DVB Frontend legacy API (a. k. a. DVBv3)</title>
<para>The usage of this API is deprecated, as it doesn't support all digital
TV standards, doesn't provide good statistics measurements and provides
incomplete information. This is kept only to support legacy applications.</para>
&sub-frontend_legacy_api;
</section>
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