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   1 #
   2 # Copyright 2008 Free Software Foundation, Inc.
   3 #
   4 # This file is part of GNU Radio
   5 #
   6 # GNU Radio is free software; you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 3, or (at your option)
   9 # any later version.
  10 #
  11 # GNU Radio is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with GNU Radio; see the file COPYING.  If not, write to
  18 # the Free Software Foundation, Inc., 51 Franklin Street,
  19 # Boston, MA 02110-1301, USA.
  20 #
  21
  22 from gnuradio import gr, window
  23 from stream_to_vector_decimator import stream_to_vector_decimator
  24 import math
  25
  26 class _logpwrfft_base(gr.hier_block2):
  27     """!
  28     Create a log10(abs(fft)) stream chain, with real or complex input.
  29     """
  30
  31     def __init__(self, sample_rate, fft_size, ref_scale, frame_rate, avg_alpha, average):
  32         """!
  33         Create an log10(abs(fft)) stream chain.
  34         Provide access to the setting the filter and sample rate.
  35         @param sample_rate        Incoming stream sample rate
  36         @param fft_size                Number of FFT bins
  37         @param ref_scale        Sets 0 dB value input amplitude
  38         @param frame_rate        Output frame rate
  39         @param avg_alpha        FFT averaging (over time) constant [0.0-1.0]
  40         @param average                Whether to average [True, False]
  41         """
  42         gr.hier_block2.__init__(self, self._name,
  43                                 gr.io_signature(1, 1, self._item_size),          # Input signature
  44                                 gr.io_signature(1, 1, gr.sizeof_float*fft_size)) # Output signature
  45
  46         self._sd = stream_to_vector_decimator(item_size=self._item_size,
  47                                               sample_rate=sample_rate,
  48                                               vec_rate=frame_rate,
  49                                               vec_len=fft_size)
  50
  51         fft_window = window.blackmanharris(fft_size)
  52         fft = self._fft_block[0](fft_size, True, fft_window)
  53         window_power = sum(map(lambda x: x*x, fft_window))
  54
  55         c2mag = gr.complex_to_mag(fft_size)
  56         self._avg = gr.single_pole_iir_filter_ff(1.0, fft_size)
  57         self._log = gr.nlog10_ff(20, fft_size,
  58                                  -10*math.log10(fft_size)              # Adjust for number of bins
  59                                  -10*math.log10(window_power/fft_size) # Adjust for windowing loss
  60                                  -20*math.log10(ref_scale/2))          # Adjust for reference scale
  61         self.connect(self, self._sd, fft, c2mag, self._avg, self._log, self)
  62         self.set_average(False)
  63         self.set_avg_alpha(avg_alpha)
  64         self.set_average(average)
  65
  66     def set_sample_rate(self, sample_rate):
  67         """!
  68         Set the new sampling rate
  69         @param sample_rate the new rate
  70         """
  71         self._sd.set_sample_rate(sample_rate)
  72
  73     def set_average(self, average):
  74         """!
  75         Set the averaging filter on/off.
  76         @param average true to set averaging on
  77         """
  78         self._average = average
  79         if self._average:
  80             self._avg.set_taps(self._avg_alpha)
  81         else:
  82             self._avg.set_taps(1.0)
  83
  84     def set_avg_alpha(self, avg_alpha):
  85         """!
  86         Set the average alpha and set the taps if average was on.
  87         @param avg_alpha the new iir filter tap
  88         """
  89         self._avg_alpha = avg_alpha
  90         self.set_average(self._average)
  91
  92     def sample_rate(self):
  93         """!
  94         Return the current sample rate.
  95         """
  96         return self._sd.sample_rate()
  97
  98     def average(self):
  99         """!
 100         Return whether or not averaging is being performed.
 101         """
 102         return self._average
 103
 104     def avg_alpha(self):
 105         """!
 106         Return averaging filter constant.
 107         """
 108         return self._avg_alpha
 109
 110 class logpwrfft_f(_logpwrfft_base):
 111         """!
 112         Create an fft block chain, with real input.
 113         """
 114         _name = "logpwrfft_f"
 115         _item_size = gr.sizeof_float
 116         _fft_block = (gr.fft_vfc, )
 117
 118 class logpwrfft_c(_logpwrfft_base):
 119         """!
 120         Create an fft block chain, with complex input.
 121         """
 122         _name = "logpwrfft_c"
 123         _item_size = gr.sizeof_gr_complex
 124         _fft_block = (gr.fft_vcc, )
 125