1 files changed, 86 insertions, 0 deletions
diff --git a/gr-vocoder/python/cvsd.py b/gr-vocoder/python/cvsd.py
new file mode 100644
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+++ b/gr-vocoder/python/cvsd.py
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+#!/usr/bin/env python
+#
+# Copyright 2007,2011 Free Software Foundation, Inc.
+# 
+# This file is part of GNU Radio
+# 
+# GNU Radio is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+# 
+# GNU Radio is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with GNU Radio; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+# 
+
+from gnuradio import gr
+import vocoder_swig
+
+class cvsd_encode_fb(gr.hier_block2):
+    '''
+    This is a wrapper for the CVSD encoder that performs interpolation and filtering
+    necessary to work with the vocoding. It converts an incoming float (+-1) to a short, scales
+    it (to 32000; slightly below the maximum value), interpolates it, and then vocodes it.
+
+    The incoming sampling rate can be anything, though, of course, the higher the sampling rate and the
+    higher the interpolation rate are, the better the sound quality.
+    '''
+    
+    def __init__(self, resample=8, bw=0.5):
+        '''
+        When using the CVSD vocoder, appropriate sampling rates are from 8k to 64k with resampling rates
+        from 1 to 8. A rate of 8k with a resampling rate of 8 provides a good quality signal.
+        '''
+
+	gr.hier_block2.__init__(self, "cvsd_encode",
+				gr.io_signature(1, 1, gr.sizeof_float), # Input signature
+				gr.io_signature(1, 1, gr.sizeof_char))  # Output signature
+
+        scale_factor = 32000.0
+        self.interp = resample
+
+        src_scale = gr.multiply_const_ff(scale_factor)
+        taps = gr.firdes.low_pass(self.interp, self.interp, bw, 2*bw)
+        interp = gr.interp_fir_filter_fff(self.interp, taps)
+        f2s = gr.float_to_short()
+        enc = vocoder_swig.cvsd_encode_sb()
+
+        self.connect(self, src_scale, interp, f2s, enc, self)
+
+
+class cvsd_decode_bf(gr.hier_block2):
+    '''
+    This is a wrapper for the CVSD decoder that performs decimation and filtering
+    necessary to work with the vocoding. It converts an incoming CVSD-encoded short to a float, decodes it
+    to a float, decimates it, and scales it (by 32000; slightly below the maximum value to avoid clipping).
+
+    The sampling rate can be anything, though, of course, the higher the sampling rate and the
+    higher the interpolation rate are, the better the sound quality.
+    '''
+
+    def __init__(self, resample=8, bw=0.5):
+        '''
+        When using the CVSD vocoder, appropriate sampling rates are from 8k to 64k with resampling rates
+        from 1 to 8. A rate of 8k with a resampling rate of 8 provides a good quality signal.
+        '''
+	gr.hier_block2.__init__(self, "cvsd_decode",
+				gr.io_signature(1, 1, gr.sizeof_char),  # Input signature
+				gr.io_signature(1, 1, gr.sizeof_float)) # Output signature
+
+        scale_factor = 32000.0
+        self.decim = resample
+
+        dec = vocoder_swig.cvsd_decode_bs()
+        s2f = gr.short_to_float()
+        taps = gr.firdes.low_pass(1, 1, bw, 2*bw)
+        decim = gr.fir_filter_fff(self.decim, taps)
+        sink_scale = gr.multiply_const_ff(1.0/scale_factor)
+
+        self.connect(self, dec, s2f, decim, sink_scale, self)