246 lines
7.6 KiB
ReStructuredText
Executable file
246 lines
7.6 KiB
ReStructuredText
Executable file
.. -*- coding: utf-8; mode: rst -*-
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.. _frontend-stat-properties:
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******************************
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Frontend statistics indicators
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******************************
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The values are returned via ``dtv_property.stat``. If the property is
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supported, ``dtv_property.stat.len`` is bigger than zero.
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For most delivery systems, ``dtv_property.stat.len`` will be 1 if the
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stats is supported, and the properties will return a single value for
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each parameter.
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It should be noted, however, that new OFDM delivery systems like ISDB
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can use different modulation types for each group of carriers. On such
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standards, up to 3 groups of statistics can be provided, and
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``dtv_property.stat.len`` is updated to reflect the "global" metrics,
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plus one metric per each carrier group (called "layer" on ISDB).
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So, in order to be consistent with other delivery systems, the first
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value at :c:type:`dtv_property.stat.dtv_stats <dtv_stats>` array refers
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to the global metric. The other elements of the array represent each
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layer, starting from layer A(index 1), layer B (index 2) and so on.
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The number of filled elements are stored at ``dtv_property.stat.len``.
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Each element of the ``dtv_property.stat.dtv_stats`` array consists on
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two elements:
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- ``svalue`` or ``uvalue``, where ``svalue`` is for signed values of
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the measure (dB measures) and ``uvalue`` is for unsigned values
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(counters, relative scale)
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- ``scale`` - Scale for the value. It can be:
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- ``FE_SCALE_NOT_AVAILABLE`` - The parameter is supported by the
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frontend, but it was not possible to collect it (could be a
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transitory or permanent condition)
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- ``FE_SCALE_DECIBEL`` - parameter is a signed value, measured in
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1/1000 dB
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- ``FE_SCALE_RELATIVE`` - parameter is a unsigned value, where 0
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means 0% and 65535 means 100%.
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- ``FE_SCALE_COUNTER`` - parameter is a unsigned value that counts
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the occurrence of an event, like bit error, block error, or lapsed
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time.
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.. _DTV-STAT-SIGNAL-STRENGTH:
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DTV_STAT_SIGNAL_STRENGTH
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========================
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Indicates the signal strength level at the analog part of the tuner or
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of the demod.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_DECIBEL`` - signal strength is in 0.001 dBm units, power
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measured in miliwatts. This value is generally negative.
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- ``FE_SCALE_RELATIVE`` - The frontend provides a 0% to 100%
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measurement for power (actually, 0 to 65535).
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.. _DTV-STAT-CNR:
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DTV_STAT_CNR
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============
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Indicates the Signal to Noise ratio for the main carrier.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_DECIBEL`` - Signal/Noise ratio is in 0.001 dB units.
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- ``FE_SCALE_RELATIVE`` - The frontend provides a 0% to 100%
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measurement for Signal/Noise (actually, 0 to 65535).
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.. _DTV-STAT-PRE-ERROR-BIT-COUNT:
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DTV_STAT_PRE_ERROR_BIT_COUNT
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============================
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Measures the number of bit errors before the forward error correction
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(FEC) on the inner coding block (before Viterbi, LDPC or other inner
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code).
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This measure is taken during the same interval as
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``DTV_STAT_PRE_TOTAL_BIT_COUNT``.
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In order to get the BER (Bit Error Rate) measurement, it should be
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divided by
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:ref:`DTV_STAT_PRE_TOTAL_BIT_COUNT <DTV-STAT-PRE-TOTAL-BIT-COUNT>`.
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This measurement is monotonically increased, as the frontend gets more
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bit count measurements. The frontend may reset it when a
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channel/transponder is tuned.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_COUNTER`` - Number of error bits counted before the inner
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coding.
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.. _DTV-STAT-PRE-TOTAL-BIT-COUNT:
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DTV_STAT_PRE_TOTAL_BIT_COUNT
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============================
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Measures the amount of bits received before the inner code block, during
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the same period as
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:ref:`DTV_STAT_PRE_ERROR_BIT_COUNT <DTV-STAT-PRE-ERROR-BIT-COUNT>`
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measurement was taken.
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It should be noted that this measurement can be smaller than the total
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amount of bits on the transport stream, as the frontend may need to
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manually restart the measurement, losing some data between each
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measurement interval.
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This measurement is monotonically increased, as the frontend gets more
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bit count measurements. The frontend may reset it when a
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channel/transponder is tuned.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_COUNTER`` - Number of bits counted while measuring
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:ref:`DTV_STAT_PRE_ERROR_BIT_COUNT <DTV-STAT-PRE-ERROR-BIT-COUNT>`.
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.. _DTV-STAT-POST-ERROR-BIT-COUNT:
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DTV_STAT_POST_ERROR_BIT_COUNT
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=============================
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Measures the number of bit errors after the forward error correction
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(FEC) done by inner code block (after Viterbi, LDPC or other inner
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code).
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This measure is taken during the same interval as
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``DTV_STAT_POST_TOTAL_BIT_COUNT``.
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In order to get the BER (Bit Error Rate) measurement, it should be
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divided by
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:ref:`DTV_STAT_POST_TOTAL_BIT_COUNT <DTV-STAT-POST-TOTAL-BIT-COUNT>`.
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This measurement is monotonically increased, as the frontend gets more
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bit count measurements. The frontend may reset it when a
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channel/transponder is tuned.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_COUNTER`` - Number of error bits counted after the inner
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coding.
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.. _DTV-STAT-POST-TOTAL-BIT-COUNT:
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DTV_STAT_POST_TOTAL_BIT_COUNT
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=============================
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Measures the amount of bits received after the inner coding, during the
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same period as
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:ref:`DTV_STAT_POST_ERROR_BIT_COUNT <DTV-STAT-POST-ERROR-BIT-COUNT>`
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measurement was taken.
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It should be noted that this measurement can be smaller than the total
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amount of bits on the transport stream, as the frontend may need to
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manually restart the measurement, losing some data between each
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measurement interval.
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This measurement is monotonically increased, as the frontend gets more
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bit count measurements. The frontend may reset it when a
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channel/transponder is tuned.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_COUNTER`` - Number of bits counted while measuring
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:ref:`DTV_STAT_POST_ERROR_BIT_COUNT <DTV-STAT-POST-ERROR-BIT-COUNT>`.
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.. _DTV-STAT-ERROR-BLOCK-COUNT:
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DTV_STAT_ERROR_BLOCK_COUNT
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==========================
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Measures the number of block errors after the outer forward error
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correction coding (after Reed-Solomon or other outer code).
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This measurement is monotonically increased, as the frontend gets more
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bit count measurements. The frontend may reset it when a
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channel/transponder is tuned.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_COUNTER`` - Number of error blocks counted after the outer
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coding.
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.. _DTV-STAT-TOTAL-BLOCK-COUNT:
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DTV-STAT_TOTAL_BLOCK_COUNT
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==========================
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Measures the total number of blocks received during the same period as
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:ref:`DTV_STAT_ERROR_BLOCK_COUNT <DTV-STAT-ERROR-BLOCK-COUNT>`
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measurement was taken.
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It can be used to calculate the PER indicator, by dividing
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:ref:`DTV_STAT_ERROR_BLOCK_COUNT <DTV-STAT-ERROR-BLOCK-COUNT>` by
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:ref:`DTV-STAT-TOTAL-BLOCK-COUNT`.
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Possible scales for this metric are:
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- ``FE_SCALE_NOT_AVAILABLE`` - it failed to measure it, or the
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measurement was not complete yet.
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- ``FE_SCALE_COUNTER`` - Number of blocks counted while measuring
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:ref:`DTV_STAT_ERROR_BLOCK_COUNT <DTV-STAT-ERROR-BLOCK-COUNT>`.
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