path: root/Documentation/DocBook/media/dvb/frontend.xml

<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 id="fe-code-rate-t">
<title>frontend code rate</title>
<para>The possible values for the <constant>fec_inner</constant> field used on
<link linkend="dvb-qpsk-parameters"><constant>struct dvb_qpsk_parameters</constant></link> and
<link linkend="dvb-qam-parameters"><constant>struct dvb_qam_parameters</constant></link> are:
</para>
<programlisting>
typedef enum fe_code_rate {
	FEC_NONE = 0,
	FEC_1_2,
	FEC_2_3,
	FEC_3_4,
	FEC_4_5,
	FEC_5_6,
	FEC_6_7,
	FEC_7_8,
	FEC_8_9,
	FEC_AUTO,
	FEC_3_5,
	FEC_9_10,
} fe_code_rate_t;
</programlisting>
<para>which correspond to error correction rates of 1/2, 2/3, etc., no error correction or auto
detection.
</para>
</section>


<section>
<title>More OFDM parameters</title>

<section id="fe-guard-interval-t">
<title>frontend guard inverval</title>
<programlisting>
typedef enum fe_guard_interval {
	GUARD_INTERVAL_1_32,
	GUARD_INTERVAL_1_16,
	GUARD_INTERVAL_1_8,
	GUARD_INTERVAL_1_4,
	GUARD_INTERVAL_AUTO,
	GUARD_INTERVAL_1_128,
	GUARD_INTERVAL_19_128,
	GUARD_INTERVAL_19_256,
} fe_guard_interval_t;
</programlisting>
</section>

<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 &#x22C6;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>