Documentation/userspace-api/media/dvb/frontend-stat-properties.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/dvb/frontend-stat-properties.rst

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Documentation/userspace-api/media/dvb/frontend-stat-properties.rst
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later

.. _frontend-stat-properties:

******************************
Frontend statistics indicators
******************************

The values are returned via ``dtv_property.stat``. If the property is
supported, ``dtv_property.stat.len`` is bigger than zero.

For most delivery systems, ``dtv_property.stat.len`` will be 1 if the
stats is supported, and the properties will return a single value for
each parameter.

It should be noted, however, that new OFDM delivery systems like ISDB
can use different modulation types for each group of carriers. On such
standards, up to 3 groups of statistics can be provided, and
``dtv_property.stat.len`` is updated to reflect the "global" metrics,
plus one metric per each carrier group (called "layer" on ISDB).

So, in order to be consistent with other delivery systems, the first
value at :c:type:`dtv_property.stat.dtv_stats <dtv_stats>` array refers
to the global metric. The other elements of the array represent each
layer, starting from layer A(index 1), layer B (index 2) and so on.

The number of filled elements are stored at ``dtv_property.stat.len``.

Each element of the ``dtv_property.stat.dtv_stats`` array consists on
two elements:

-  ``svalue`` or ``uvalue``, where ``svalue`` is for signed values of
   the measure (dB measures) and ``uvalue`` is for unsigned values
   (counters, relative scale)

-  ``scale`` - Scale for the value. It can be:

   -  ``FE_SCALE_NOT_AVAILABLE`` - The parameter is supported by the
      frontend, but it was not possible to collect it (could be a
      transitory or permanent condition)

   -  ``FE_SCALE_DECIBEL`` - parameter is a signed value, measured in
      1/1000 dB

   -  ``FE_SCALE_RELATIVE`` - parameter is a unsigned value, where 0
      means 0% and 65535 means 100%.

   -  ``FE_SCALE_COUNTER`` - parameter is a unsigned value that counts
      the occurrence of an event, like bit error, block error, or lapsed
      time.


.. _DTV-STAT-SIGNAL-STRENGTH:

DTV_STAT_SIGNAL_STRENGTH
========================

Indicates the signal strength level at the analog part of the tuner or
of the demod.

Possible scales for this metric are:

-  ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
   measurement was not complete yet.

-  ``FE_SCALE_DECIBEL`` - signal strength is in 0.001 dBm units, power
   measured in miliwatts. This value is generally negative.

-  ``FE_SCALE_RELATIVE`` - The frontend provides a 0% to 100%
   measurement for power (actually, 0 to 65535).

Annotation

Implementation Notes