diff options
| author | Marcus Müller <mmueller@gnuradio.org> | 2021-04-18 15:39:40 +0200 |
|---|---|---|
| committer | mormj <34754695+mormj@users.noreply.github.com> | 2021-04-21 13:58:23 -0400 |
| commit | 8f9c66bf0b4099cd824745bbbdcde2285db78cf9 (patch) | |
| tree | 25fbe456efb2a3a7fd40e4d632a7a94ee38fb344 /gr-filter | |
| parent | 0b3dc1b157b709fcd64a80f13ec604bda3f86e66 (diff) | |
filter: filter_delay_fc documentation used to be unclear about delay
This clarifies that the block does not, indeed, construct a
delay-compensating all-pass, but just takes half the length of the
passed taps vector and uses that as delay.
Signed-off-by: Marcus Müller <mmueller@gnuradio.org>
Diffstat (limited to 'gr-filter')
| -rw-r--r-- | gr-filter/include/gnuradio/filter/filter_delay_fc.h | 35 | ||||
| -rw-r--r-- | gr-filter/python/filter/bindings/filter_delay_fc_python.cc | 2 |
2 files changed, 23 insertions, 14 deletions
diff --git a/gr-filter/include/gnuradio/filter/filter_delay_fc.h b/gr-filter/include/gnuradio/filter/filter_delay_fc.h index 349592085b..c8c4f27413 100644 --- a/gr-filter/include/gnuradio/filter/filter_delay_fc.h +++ b/gr-filter/include/gnuradio/filter/filter_delay_fc.h @@ -1,6 +1,7 @@ /* -*- c++ -*- */ /* * Copyright 2004,2012 Free Software Foundation, Inc. + * Copyright 2021 Marcus Müller * * This file is part of GNU Radio * @@ -18,33 +19,41 @@ namespace gr { namespace filter { /*! - * \brief Filter-Delay Combination Block. + * \brief Filter-Delay Combination Block * \ingroup filter_blk * * \details - * The block takes one or two float stream and outputs a complex - * stream. + * The purpose of this block is to compensate the delay that a linear-phase filter + * introduces. * - * If only one float stream is input, the real output is a delayed - * version of this input and the imaginary output is the filtered - * output. + * It does that by introducing a delay of half the length of the FIR tap vector on + * passed-through samples. * - * If two floats are connected to the input, then the real output - * is the delayed version of the first input, and the imaginary - * output is the filtered output. + * The block takes one or two float stream and outputs a stream composed of pairs of + * floats. (In GNU Radio, pairs of floats are identical to complex numbers, where the real + * and imaginary parts are the first and second element, respectively.) * - * The delay in the real path accounts for the group delay - * introduced by the filter in the imaginary path. The filter taps - * needs to be calculated before initializing this block. + * If only one float stream is input, the first element of each output item is a delayed + * version of this input and the second element is the filtered output. + * + * If two floats are connected to the input, then the first element of each output item is + * the delayed version of the first input, and the second element is the filtered second + * input. + * + * The delay in the first elements of the output accounts for the group delay introduced + * by the filter in the second elements path under the assumption of linear-phase + * filtering. The filter taps need to be calculated before initializing this block. */ class FILTER_API filter_delay_fc : virtual public sync_block { public: - // gr::filter::filter_delay_fc::sptr typedef std::shared_ptr<filter_delay_fc> sptr; /*! * Build a filter with delay block. + * + * \param taps the vector of real-valued tags. Half of the length of this vector is + * the delay introduced by this block. */ static sptr make(const std::vector<float>& taps); }; diff --git a/gr-filter/python/filter/bindings/filter_delay_fc_python.cc b/gr-filter/python/filter/bindings/filter_delay_fc_python.cc index 98816ecbc4..506a343728 100644 --- a/gr-filter/python/filter/bindings/filter_delay_fc_python.cc +++ b/gr-filter/python/filter/bindings/filter_delay_fc_python.cc @@ -14,7 +14,7 @@ /* BINDTOOL_GEN_AUTOMATIC(0) */ /* BINDTOOL_USE_PYGCCXML(0) */ /* BINDTOOL_HEADER_FILE(filter_delay_fc.h) */ -/* BINDTOOL_HEADER_FILE_HASH(eea88abd944cadd21cdfdb0211654fcc) */ +/* BINDTOOL_HEADER_FILE_HASH(318340909cbdad8f966383445fdec0f4) */ /***********************************************************************************/ #include <pybind11/complex.h> |