1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 3.. c:type:: dvb_frontend_parameters 4 5******************* 6frontend parameters 7******************* 8 9The kind of parameters passed to the frontend device for tuning depend 10on the kind of hardware you are using. 11 12The struct ``dvb_frontend_parameters`` uses a union with specific 13per-system parameters. However, as newer delivery systems required more 14data, the structure size weren't enough to fit, and just extending its 15size would break the existing applications. So, those parameters were 16replaced by the usage of 17:ref:`FE_GET_PROPERTY/FE_SET_PROPERTY <FE_GET_PROPERTY>` 18ioctl's. The new API is flexible enough to add new parameters to 19existing delivery systems, and to add newer delivery systems. 20 21So, newer applications should use 22:ref:`FE_GET_PROPERTY/FE_SET_PROPERTY <FE_GET_PROPERTY>` 23instead, in order to be able to support the newer System Delivery like 24DVB-S2, DVB-T2, DVB-C2, ISDB, etc. 25 26All kinds of parameters are combined as a union in the 27``dvb_frontend_parameters`` structure: 28 29 30.. code-block:: c 31 32 struct dvb_frontend_parameters { 33 uint32_t frequency; /* (absolute) frequency in Hz for QAM/OFDM */ 34 /* intermediate frequency in kHz for QPSK */ 35 fe_spectral_inversion_t inversion; 36 union { 37 struct dvb_qpsk_parameters qpsk; 38 struct dvb_qam_parameters qam; 39 struct dvb_ofdm_parameters ofdm; 40 struct dvb_vsb_parameters vsb; 41 } u; 42 }; 43 44In the case of QPSK frontends the ``frequency`` field specifies the 45intermediate frequency, i.e. the offset which is effectively added to 46the local oscillator frequency (LOF) of the LNB. The intermediate 47frequency has to be specified in units of kHz. For QAM and OFDM 48frontends the ``frequency`` specifies the absolute frequency and is 49given in Hz. 50 51 52.. c:type:: dvb_qpsk_parameters 53 54QPSK parameters 55=============== 56 57For satellite QPSK frontends you have to use the ``dvb_qpsk_parameters`` 58structure: 59 60 61.. code-block:: c 62 63 struct dvb_qpsk_parameters { 64 uint32_t symbol_rate; /* symbol rate in Symbols per second */ 65 fe_code_rate_t fec_inner; /* forward error correction (see above) */ 66 }; 67 68 69.. c:type:: dvb_qam_parameters 70 71QAM parameters 72============== 73 74for cable QAM frontend you use the ``dvb_qam_parameters`` structure: 75 76 77.. code-block:: c 78 79 struct dvb_qam_parameters { 80 uint32_t symbol_rate; /* symbol rate in Symbols per second */ 81 fe_code_rate_t fec_inner; /* forward error correction (see above) */ 82 fe_modulation_t modulation; /* modulation type (see above) */ 83 }; 84 85 86.. c:type:: dvb_vsb_parameters 87 88VSB parameters 89============== 90 91ATSC frontends are supported by the ``dvb_vsb_parameters`` structure: 92 93 94.. code-block:: c 95 96 struct dvb_vsb_parameters { 97 fe_modulation_t modulation; /* modulation type (see above) */ 98 }; 99 100 101.. c:type:: dvb_ofdm_parameters 102 103OFDM parameters 104=============== 105 106DVB-T frontends are supported by the ``dvb_ofdm_parameters`` structure: 107 108 109.. code-block:: c 110 111 struct dvb_ofdm_parameters { 112 fe_bandwidth_t bandwidth; 113 fe_code_rate_t code_rate_HP; /* high priority stream code rate */ 114 fe_code_rate_t code_rate_LP; /* low priority stream code rate */ 115 fe_modulation_t constellation; /* modulation type (see above) */ 116 fe_transmit_mode_t transmission_mode; 117 fe_guard_interval_t guard_interval; 118 fe_hierarchy_t hierarchy_information; 119 }; 120