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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. c:type:: 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 a 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 a union in the
+``dvb_frontend_parameters`` 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.
+
+
+.. c:type:: 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) */
+ };
+
+
+.. c:type:: 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) */
+ };
+
+
+.. c:type:: 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) */
+ };
+
+
+.. c:type:: 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;
+ };