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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _dvb-frontend-parameters:
+
+*******************
+frontend parameters
+*******************
+
+The kind of parameters passed to the frontend device for tuning depend
+on the kind of hardware you are using.
+
+The struct ``dvb_frontend_parameters`` uses an union with specific
+per-system parameters. However, as newer delivery systems required more
+data, the structure size weren't enough to fit, and just extending its
+size would break the existing applications. So, those parameters were
+replaced by the usage of
+:ref:`FE_GET_PROPERTY/FE_SET_PROPERTY <FE_GET_PROPERTY>`
+ioctl's. The new API is flexible enough to add new parameters to
+existing delivery systems, and to add newer delivery systems.
+
+So, newer applications should use
+:ref:`FE_GET_PROPERTY/FE_SET_PROPERTY <FE_GET_PROPERTY>`
+instead, in order to be able to support the newer System Delivery like
+DVB-S2, DVB-T2, DVB-C2, ISDB, etc.
+
+All kinds of parameters are combined as an union in the
+FrontendParameters structure:
+
+
+.. code-block:: c
+
+    struct dvb_frontend_parameters {
+	uint32_t frequency;     /* (absolute) frequency in Hz for QAM/OFDM */
+		    /* intermediate frequency in kHz for QPSK */
+	fe_spectral_inversion_t inversion;
+	union {
+	    struct dvb_qpsk_parameters qpsk;
+	    struct dvb_qam_parameters  qam;
+	    struct dvb_ofdm_parameters ofdm;
+	    struct dvb_vsb_parameters  vsb;
+	} u;
+    };
+
+In the case of QPSK frontends the ``frequency`` field specifies the
+intermediate frequency, i.e. the offset which is effectively added to
+the local oscillator frequency (LOF) of the LNB. The intermediate
+frequency has to be specified in units of kHz. For QAM and OFDM
+frontends the ``frequency`` specifies the absolute frequency and is
+given in Hz.
+
+
+.. _dvb-qpsk-parameters:
+
+QPSK parameters
+===============
+
+For satellite QPSK frontends you have to use the ``dvb_qpsk_parameters``
+structure:
+
+
+.. code-block:: c
+
+     struct dvb_qpsk_parameters {
+	 uint32_t        symbol_rate;  /* symbol rate in Symbols per second */
+	 fe_code_rate_t  fec_inner;    /* forward error correction (see above) */
+     };
+
+
+.. _dvb-qam-parameters:
+
+QAM parameters
+==============
+
+for cable QAM frontend you use the ``dvb_qam_parameters`` structure:
+
+
+.. code-block:: c
+
+     struct dvb_qam_parameters {
+	 uint32_t         symbol_rate; /* symbol rate in Symbols per second */
+	 fe_code_rate_t   fec_inner;   /* forward error correction (see above) */
+	 fe_modulation_t  modulation;  /* modulation type (see above) */
+     };
+
+
+.. _dvb-vsb-parameters:
+
+VSB parameters
+==============
+
+ATSC frontends are supported by the ``dvb_vsb_parameters`` structure:
+
+
+.. code-block:: c
+
+    struct dvb_vsb_parameters {
+	fe_modulation_t modulation; /* modulation type (see above) */
+    };
+
+
+.. _dvb-ofdm-parameters:
+
+OFDM parameters
+===============
+
+DVB-T frontends are supported by the ``dvb_ofdm_parameters`` structure:
+
+
+.. code-block:: c
+
+     struct dvb_ofdm_parameters {
+	 fe_bandwidth_t      bandwidth;
+	 fe_code_rate_t      code_rate_HP;  /* high priority stream code rate */
+	 fe_code_rate_t      code_rate_LP;  /* low priority stream code rate */
+	 fe_modulation_t     constellation; /* modulation type (see above) */
+	 fe_transmit_mode_t  transmission_mode;
+	 fe_guard_interval_t guard_interval;
+	 fe_hierarchy_t      hierarchy_information;
+     };