1 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
2
3 /*
4 QM DSP Library
5
6 Centre for Digital Music, Queen Mary, University of London.
7 This file 2005-2006 Christian Landone.
8
9 This program is free software; you can redistribute it and/or
10 modify it under the terms of the GNU General Public License as
11 published by the Free Software Foundation; either version 2 of the
12 License, or (at your option) any later version. See the file
13 COPYING included with this distribution for more information.
14 */
15
16 #include "Decimator.h"
17
18 #include <iostream>
19
20 //////////////////////////////////////////////////////////////////////
21 // Construction/Destruction
22 //////////////////////////////////////////////////////////////////////
23
Decimator(int inLength,int decFactor)24 Decimator::Decimator( int inLength, int decFactor )
25 {
26 m_inputLength = 0;
27 m_outputLength = 0;
28 m_decFactor = 1;
29
30 initialise( inLength, decFactor );
31 }
32
~Decimator()33 Decimator::~Decimator()
34 {
35 deInitialise();
36 }
37
initialise(int inLength,int decFactor)38 void Decimator::initialise( int inLength, int decFactor)
39 {
40 m_inputLength = inLength;
41 m_decFactor = decFactor;
42 m_outputLength = m_inputLength / m_decFactor;
43
44 decBuffer = new double[ m_inputLength ];
45
46 // If adding new factors here, add them to
47 // getHighestSupportedFactor in the header as well
48
49 if(m_decFactor == 8) {
50
51 //////////////////////////////////////////////////
52 b[0] = 0.060111378492136;
53 b[1] = -0.257323420830598;
54 b[2] = 0.420583503165928;
55 b[3] = -0.222750785197418;
56 b[4] = -0.222750785197418;
57 b[5] = 0.420583503165928;
58 b[6] = -0.257323420830598;
59 b[7] = 0.060111378492136;
60
61 a[0] = 1;
62 a[1] = -5.667654878577432;
63 a[2] = 14.062452278088417;
64 a[3] = -19.737303840697738;
65 a[4] = 16.889698874608641;
66 a[5] = -8.796600612325928;
67 a[6] = 2.577553446979888;
68 a[7] = -0.326903916815751;
69 //////////////////////////////////////////////////
70
71 } else if( m_decFactor == 4 ) {
72
73 //////////////////////////////////////////////////
74 b[ 0 ] = 0.10133306904918619;
75 b[ 1 ] = -0.2447523353702363;
76 b[ 2 ] = 0.33622528590120965;
77 b[ 3 ] = -0.13936581560633518;
78 b[ 4 ] = -0.13936581560633382;
79 b[ 5 ] = 0.3362252859012087;
80 b[ 6 ] = -0.2447523353702358;
81 b[ 7 ] = 0.10133306904918594;
82
83 a[ 0 ] = 1;
84 a[ 1 ] = -3.9035590278139427;
85 a[ 2 ] = 7.5299379980621133;
86 a[ 3 ] = -8.6890803793177511;
87 a[ 4 ] = 6.4578667096099176;
88 a[ 5 ] = -3.0242979431223631;
89 a[ 6 ] = 0.83043385136748382;
90 a[ 7 ] = -0.094420800837809335;
91 //////////////////////////////////////////////////
92
93 } else if( m_decFactor == 2 ) {
94
95 //////////////////////////////////////////////////
96 b[ 0 ] = 0.20898944260075727;
97 b[ 1 ] = 0.40011234879814367;
98 b[ 2 ] = 0.819741973072733;
99 b[ 3 ] = 1.0087419911682323;
100 b[ 4 ] = 1.0087419911682325;
101 b[ 5 ] = 0.81974197307273156;
102 b[ 6 ] = 0.40011234879814295;
103 b[ 7 ] = 0.20898944260075661;
104
105 a[ 0 ] = 1;
106 a[ 1 ] = 0.0077331184208358217;
107 a[ 2 ] = 1.9853971155964376;
108 a[ 3 ] = 0.19296739275341004;
109 a[ 4 ] = 1.2330748872852182;
110 a[ 5 ] = 0.18705341389316466;
111 a[ 6 ] = 0.23659265908013868;
112 a[ 7 ] = 0.032352924250533946;
113
114 } else {
115
116 if ( m_decFactor != 1 ) {
117 std::cerr << "WARNING: Decimator::initialise: unsupported decimation factor " << m_decFactor << ", no antialiasing filter will be used" << std::endl;
118 }
119
120 //////////////////////////////////////////////////
121 b[ 0 ] = 1;
122 b[ 1 ] = 0;
123 b[ 2 ] = 0;
124 b[ 3 ] = 0;
125 b[ 4 ] = 0;
126 b[ 5 ] = 0;
127 b[ 6 ] = 0;
128 b[ 7 ] = 0;
129
130 a[ 0 ] = 1;
131 a[ 1 ] = 0;
132 a[ 2 ] = 0;
133 a[ 3 ] = 0;
134 a[ 4 ] = 0;
135 a[ 5 ] = 0;
136 a[ 6 ] = 0;
137 a[ 7 ] = 0;
138 }
139
140 resetFilter();
141 }
142
deInitialise()143 void Decimator::deInitialise()
144 {
145 delete [] decBuffer;
146 }
147
resetFilter()148 void Decimator::resetFilter()
149 {
150 Input = Output = 0;
151
152 o1=o2=o3=o4=o5=o6=o7=0;
153 }
154
doAntiAlias(const double * src,double * dst,int length)155 void Decimator::doAntiAlias(const double *src, double *dst, int length)
156 {
157 for (int i = 0; i < length; i++ ) {
158
159 Input = (double)src[ i ];
160
161 Output = Input * b[ 0 ] + o1;
162
163 o1 = Input * b[ 1 ] - Output * a[ 1 ] + o2;
164 o2 = Input * b[ 2 ] - Output * a[ 2 ] + o3;
165 o3 = Input * b[ 3 ] - Output * a[ 3 ] + o4;
166 o4 = Input * b[ 4 ] - Output * a[ 4 ] + o5;
167 o5 = Input * b[ 5 ] - Output * a[ 5 ] + o6;
168 o6 = Input * b[ 6 ] - Output * a[ 6 ] + o7;
169 o7 = Input * b[ 7 ] - Output * a[ 7 ] ;
170
171 dst[ i ] = Output;
172 }
173 }
174
doAntiAlias(const float * src,double * dst,int length)175 void Decimator::doAntiAlias(const float *src, double *dst, int length)
176 {
177 for (int i = 0; i < length; i++ ) {
178
179 Input = (double)src[ i ];
180
181 Output = Input * b[ 0 ] + o1;
182
183 o1 = Input * b[ 1 ] - Output * a[ 1 ] + o2;
184 o2 = Input * b[ 2 ] - Output * a[ 2 ] + o3;
185 o3 = Input * b[ 3 ] - Output * a[ 3 ] + o4;
186 o4 = Input * b[ 4 ] - Output * a[ 4 ] + o5;
187 o5 = Input * b[ 5 ] - Output * a[ 5 ] + o6;
188 o6 = Input * b[ 6 ] - Output * a[ 6 ] + o7;
189 o7 = Input * b[ 7 ] - Output * a[ 7 ] ;
190
191 dst[ i ] = Output;
192 }
193 }
194
process(const double * src,double * dst)195 void Decimator::process(const double *src, double *dst)
196 {
197 if (m_decFactor == 1) {
198 for (int i = 0; i < m_outputLength; i++ ) {
199 dst[i] = src[i];
200 }
201 return;
202 }
203
204 doAntiAlias( src, decBuffer, m_inputLength );
205
206 int idx = 0;
207
208 for (int i = 0; i < m_outputLength; i++ ) {
209 dst[ idx++ ] = decBuffer[ m_decFactor * i ];
210 }
211 }
212
process(const float * src,float * dst)213 void Decimator::process(const float *src, float *dst)
214 {
215 if (m_decFactor == 1) {
216 for (int i = 0; i < m_outputLength; i++ ) {
217 dst[i] = src[i];
218 }
219 return;
220 }
221
222 doAntiAlias( src, decBuffer, m_inputLength );
223
224 int idx = 0;
225
226 for (int i = 0; i < m_outputLength; i++ ) {
227 dst[ idx++ ] = decBuffer[ m_decFactor * i ];
228 }
229 }
230