summaryrefslogtreecommitdiff
path: root/Documentation/media/uapi/dvb/dvb-frontend-parameters.rst
diff options
context:
space:
mode:
authorMauro Carvalho Chehab <mchehab@s-opensource.com>2016-07-08 11:40:06 -0300
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2016-07-08 11:59:40 -0300
commit60c2820d0f6d3497975b6488e2599f8f611d8b95 (patch)
treeb3b03707c6438ea9b99cc57e847ebf517f968ab1 /Documentation/media/uapi/dvb/dvb-frontend-parameters.rst
parenta97369b5e21ea9b8b5fef7c0f4f48bbe60c07ca3 (diff)
doc_rst: rename the media Sphinx suff to Documentation/media
The name of the subsystem is "media", and not "linux_tv". Also, as we plan to add other stuff there in the future, let's rename also the media uAPI book to media_uapi, to make it clearer. No functional changes. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'Documentation/media/uapi/dvb/dvb-frontend-parameters.rst')
-rw-r--r--Documentation/media/uapi/dvb/dvb-frontend-parameters.rst119
1 files changed, 119 insertions, 0 deletions
diff --git a/Documentation/media/uapi/dvb/dvb-frontend-parameters.rst b/Documentation/media/uapi/dvb/dvb-frontend-parameters.rst
new file mode 100644
index 000000000000..16cb581d5cff
--- /dev/null
+++ b/Documentation/media/uapi/dvb/dvb-frontend-parameters.rst
@@ -0,0 +1,119 @@
+.. -*- 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;
+ };