summaryrefslogtreecommitdiffstats
path: root/Documentation/userspace-api/media/dvb/dvbproperty.rst
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--Documentation/userspace-api/media/dvb/dvbproperty.rst126
1 files changed, 126 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/dvb/dvbproperty.rst b/Documentation/userspace-api/media/dvb/dvbproperty.rst
new file mode 100644
index 000000000..981da20af
--- /dev/null
+++ b/Documentation/userspace-api/media/dvb/dvbproperty.rst
@@ -0,0 +1,126 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _frontend-properties:
+
+**************
+Property types
+**************
+
+Tuning into a Digital TV physical channel and starting decoding it
+requires changing a set of parameters, in order to control the tuner,
+the demodulator, the Linear Low-noise Amplifier (LNA) and to set the
+antenna subsystem via Satellite Equipment Control - SEC (on satellite
+systems). The actual parameters are specific to each particular digital
+TV standards, and may change as the digital TV specs evolves.
+
+In the past (up to DVB API version 3 - DVBv3), the strategy used was to have a
+union with the parameters needed to tune for DVB-S, DVB-C, DVB-T and
+ATSC delivery systems grouped there. The problem is that, as the second
+generation standards appeared, the size of such union was not big
+enough to group the structs that would be required for those new
+standards. Also, extending it would break userspace.
+
+So, the legacy union/struct based approach was deprecated, in favor
+of a properties set approach. On such approach,
+:ref:`FE_GET_PROPERTY and FE_SET_PROPERTY <FE_GET_PROPERTY>` are used
+to setup the frontend and read its status.
+
+The actual action is determined by a set of dtv_property cmd/data pairs.
+With one single ioctl, is possible to get/set up to 64 properties.
+
+This section describes the new and recommended way to set the frontend,
+with supports all digital TV delivery systems.
+
+.. note::
+
+ 1. On Linux DVB API version 3, setting a frontend was done via
+ struct :c:type:`dvb_frontend_parameters`.
+
+ 2. Don't use DVB API version 3 calls on hardware with supports
+ newer standards. Such API provides no support or a very limited
+ support to new standards and/or new hardware.
+
+ 3. Nowadays, most frontends support multiple delivery systems.
+ Only with DVB API version 5 calls it is possible to switch between
+ the multiple delivery systems supported by a frontend.
+
+ 4. DVB API version 5 is also called *S2API*, as the first
+ new standard added to it was DVB-S2.
+
+**Example**: in order to set the hardware to tune into a DVB-C channel
+at 651 kHz, modulated with 256-QAM, FEC 3/4 and symbol rate of 5.217
+Mbauds, those properties should be sent to
+:ref:`FE_SET_PROPERTY <FE_GET_PROPERTY>` ioctl:
+
+ :ref:`DTV_DELIVERY_SYSTEM <DTV-DELIVERY-SYSTEM>` = SYS_DVBC_ANNEX_A
+
+ :ref:`DTV_FREQUENCY <DTV-FREQUENCY>` = 651000000
+
+ :ref:`DTV_MODULATION <DTV-MODULATION>` = QAM_256
+
+ :ref:`DTV_INVERSION <DTV-INVERSION>` = INVERSION_AUTO
+
+ :ref:`DTV_SYMBOL_RATE <DTV-SYMBOL-RATE>` = 5217000
+
+ :ref:`DTV_INNER_FEC <DTV-INNER-FEC>` = FEC_3_4
+
+ :ref:`DTV_TUNE <DTV-TUNE>`
+
+The code that would that would do the above is show in
+:ref:`dtv-prop-example`.
+
+.. code-block:: c
+ :caption: Example: Setting digital TV frontend properties
+ :name: dtv-prop-example
+
+ #include <stdio.h>
+ #include <fcntl.h>
+ #include <sys/ioctl.h>
+ #include <linux/dvb/frontend.h>
+
+ static struct dtv_property props[] = {
+ { .cmd = DTV_DELIVERY_SYSTEM, .u.data = SYS_DVBC_ANNEX_A },
+ { .cmd = DTV_FREQUENCY, .u.data = 651000000 },
+ { .cmd = DTV_MODULATION, .u.data = QAM_256 },
+ { .cmd = DTV_INVERSION, .u.data = INVERSION_AUTO },
+ { .cmd = DTV_SYMBOL_RATE, .u.data = 5217000 },
+ { .cmd = DTV_INNER_FEC, .u.data = FEC_3_4 },
+ { .cmd = DTV_TUNE }
+ };
+
+ static struct dtv_properties dtv_prop = {
+ .num = 6, .props = props
+ };
+
+ int main(void)
+ {
+ int fd = open("/dev/dvb/adapter0/frontend0", O_RDWR);
+
+ if (!fd) {
+ perror ("open");
+ return -1;
+ }
+ if (ioctl(fd, FE_SET_PROPERTY, &dtv_prop) == -1) {
+ perror("ioctl");
+ return -1;
+ }
+ printf("Frontend set\\n");
+ return 0;
+ }
+
+.. attention:: While it is possible to directly call the Kernel code like the
+ above example, it is strongly recommended to use
+ `libdvbv5 <https://linuxtv.org/docs/libdvbv5/index.html>`__, as it
+ provides abstraction to work with the supported digital TV standards and
+ provides methods for usual operations like program scanning and to
+ read/write channel descriptor files.
+
+.. toctree::
+ :maxdepth: 1
+
+ fe_property_parameters
+ frontend-stat-properties
+ frontend-property-terrestrial-systems
+ frontend-property-cable-systems
+ frontend-property-satellite-systems
+ frontend-header