1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/media/uapi/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. c:type:: dvb_frontend_parameters 11 12******************* 13frontend parameters 14******************* 15 16The kind of parameters passed to the frontend device for tuning depend 17on the kind of hardware you are using. 18 19The struct ``dvb_frontend_parameters`` uses a union with specific 20per-system parameters. However, as newer delivery systems required more 21data, the structure size weren't enough to fit, and just extending its 22size would break the existing applications. So, those parameters were 23replaced by the usage of 24:ref:`FE_GET_PROPERTY/FE_SET_PROPERTY <FE_GET_PROPERTY>` 25ioctl's. The new API is flexible enough to add new parameters to 26existing delivery systems, and to add newer delivery systems. 27 28So, newer applications should use 29:ref:`FE_GET_PROPERTY/FE_SET_PROPERTY <FE_GET_PROPERTY>` 30instead, in order to be able to support the newer System Delivery like 31DVB-S2, DVB-T2, DVB-C2, ISDB, etc. 32 33All kinds of parameters are combined as a union in the 34``dvb_frontend_parameters`` structure: 35 36 37.. code-block:: c 38 39 struct dvb_frontend_parameters { 40 uint32_t frequency; /* (absolute) frequency in Hz for QAM/OFDM */ 41 /* intermediate frequency in kHz for QPSK */ 42 fe_spectral_inversion_t inversion; 43 union { 44 struct dvb_qpsk_parameters qpsk; 45 struct dvb_qam_parameters qam; 46 struct dvb_ofdm_parameters ofdm; 47 struct dvb_vsb_parameters vsb; 48 } u; 49 }; 50 51In the case of QPSK frontends the ``frequency`` field specifies the 52intermediate frequency, i.e. the offset which is effectively added to 53the local oscillator frequency (LOF) of the LNB. The intermediate 54frequency has to be specified in units of kHz. For QAM and OFDM 55frontends the ``frequency`` specifies the absolute frequency and is 56given in Hz. 57 58 59.. c:type:: dvb_qpsk_parameters 60 61QPSK parameters 62=============== 63 64For satellite QPSK frontends you have to use the ``dvb_qpsk_parameters`` 65structure: 66 67 68.. code-block:: c 69 70 struct dvb_qpsk_parameters { 71 uint32_t symbol_rate; /* symbol rate in Symbols per second */ 72 fe_code_rate_t fec_inner; /* forward error correction (see above) */ 73 }; 74 75 76.. c:type:: dvb_qam_parameters 77 78QAM parameters 79============== 80 81for cable QAM frontend you use the ``dvb_qam_parameters`` structure: 82 83 84.. code-block:: c 85 86 struct dvb_qam_parameters { 87 uint32_t symbol_rate; /* symbol rate in Symbols per second */ 88 fe_code_rate_t fec_inner; /* forward error correction (see above) */ 89 fe_modulation_t modulation; /* modulation type (see above) */ 90 }; 91 92 93.. c:type:: dvb_vsb_parameters 94 95VSB parameters 96============== 97 98ATSC frontends are supported by the ``dvb_vsb_parameters`` structure: 99 100 101.. code-block:: c 102 103 struct dvb_vsb_parameters { 104 fe_modulation_t modulation; /* modulation type (see above) */ 105 }; 106 107 108.. c:type:: dvb_ofdm_parameters 109 110OFDM parameters 111=============== 112 113DVB-T frontends are supported by the ``dvb_ofdm_parameters`` structure: 114 115 116.. code-block:: c 117 118 struct dvb_ofdm_parameters { 119 fe_bandwidth_t bandwidth; 120 fe_code_rate_t code_rate_HP; /* high priority stream code rate */ 121 fe_code_rate_t code_rate_LP; /* low priority stream code rate */ 122 fe_modulation_t constellation; /* modulation type (see above) */ 123 fe_transmit_mode_t transmission_mode; 124 fe_guard_interval_t guard_interval; 125 fe_hierarchy_t hierarchy_information; 126 }; 127