media/libsoundtouch/src/InterpolateShannon.cpp@b8a032363ba2
media/libsoundtouch/src/InterpolateShannon.cpp
Thu, 22 Jan 2015 13:21:57 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 22 Jan 2015 13:21:57 +0100
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
- permissions
- -rw-r--r--
Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6
1 ////////////////////////////////////////////////////////////////////////////////
2 ///
3 /// Sample interpolation routine using 8-tap band-limited Shannon interpolation
4 /// with kaiser window.
5 ///
6 /// Notice. This algorithm is remarkably much heavier than linear or cubic
7 /// interpolation, and not remarkably better than cubic algorithm. Thus mostly
8 /// for experimental purposes
9 ///
10 /// Author : Copyright (c) Olli Parviainen
11 /// Author e-mail : oparviai 'at' iki.fi
12 /// SoundTouch WWW: http://www.surina.net/soundtouch
13 ///
14 ////////////////////////////////////////////////////////////////////////////////
15 //
16 // $Id: InterpolateShannon.cpp 195 2014-04-06 15:57:21Z oparviai $
17 //
18 ////////////////////////////////////////////////////////////////////////////////
19 //
20 // License :
21 //
22 // SoundTouch audio processing library
23 // Copyright (c) Olli Parviainen
24 //
25 // This library is free software; you can redistribute it and/or
26 // modify it under the terms of the GNU Lesser General Public
27 // License as published by the Free Software Foundation; either
28 // version 2.1 of the License, or (at your option) any later version.
29 //
30 // This library is distributed in the hope that it will be useful,
31 // but WITHOUT ANY WARRANTY; without even the implied warranty of
32 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
33 // Lesser General Public License for more details.
34 //
35 // You should have received a copy of the GNU Lesser General Public
36 // License along with this library; if not, write to the Free Software
37 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
38 //
39 ////////////////////////////////////////////////////////////////////////////////
41 #include <math.h>
42 #include "InterpolateShannon.h"
43 #include "STTypes.h"
45 using namespace soundtouch;
48 /// Kaiser window with beta = 2.0
49 /// Values scaled down by 5% to avoid overflows
50 static const double _kaiser8[8] =
51 {
52 0.41778693317814,
53 0.64888025049173,
54 0.83508562409944,
55 0.93887857733412,
56 0.93887857733412,
57 0.83508562409944,
58 0.64888025049173,
59 0.41778693317814
60 };
63 InterpolateShannon::InterpolateShannon()
64 {
65 fract = 0;
66 }
69 void InterpolateShannon::resetRegisters()
70 {
71 fract = 0;
72 }
75 #define PI 3.1415926536
76 #define sinc(x) (sin(PI * (x)) / (PI * (x)))
78 /// Transpose mono audio. Returns number of produced output samples, and
79 /// updates "srcSamples" to amount of consumed source samples
80 int InterpolateShannon::transposeMono(SAMPLETYPE *pdest,
81 const SAMPLETYPE *psrc,
82 int &srcSamples)
83 {
84 int i;
85 int srcSampleEnd = srcSamples - 8;
86 int srcCount = 0;
88 i = 0;
89 while (srcCount < srcSampleEnd)
90 {
91 double out;
92 assert(fract < 1.0);
94 out = psrc[0] * sinc(-3.0 - fract) * _kaiser8[0];
95 out += psrc[1] * sinc(-2.0 - fract) * _kaiser8[1];
96 out += psrc[2] * sinc(-1.0 - fract) * _kaiser8[2];
97 if (fract < 1e-6)
98 {
99 out += psrc[3] * _kaiser8[3]; // sinc(0) = 1
100 }
101 else
102 {
103 out += psrc[3] * sinc(- fract) * _kaiser8[3];
104 }
105 out += psrc[4] * sinc( 1.0 - fract) * _kaiser8[4];
106 out += psrc[5] * sinc( 2.0 - fract) * _kaiser8[5];
107 out += psrc[6] * sinc( 3.0 - fract) * _kaiser8[6];
108 out += psrc[7] * sinc( 4.0 - fract) * _kaiser8[7];
110 pdest[i] = (SAMPLETYPE)out;
111 i ++;
113 // update position fraction
114 fract += rate;
115 // update whole positions
116 int whole = (int)fract;
117 fract -= whole;
118 psrc += whole;
119 srcCount += whole;
120 }
121 srcSamples = srcCount;
122 return i;
123 }
126 /// Transpose stereo audio. Returns number of produced output samples, and
127 /// updates "srcSamples" to amount of consumed source samples
128 int InterpolateShannon::transposeStereo(SAMPLETYPE *pdest,
129 const SAMPLETYPE *psrc,
130 int &srcSamples)
131 {
132 int i;
133 int srcSampleEnd = srcSamples - 8;
134 int srcCount = 0;
136 i = 0;
137 while (srcCount < srcSampleEnd)
138 {
139 double out0, out1, w;
140 assert(fract < 1.0);
142 w = sinc(-3.0 - fract) * _kaiser8[0];
143 out0 = psrc[0] * w; out1 = psrc[1] * w;
144 w = sinc(-2.0 - fract) * _kaiser8[1];
145 out0 += psrc[2] * w; out1 += psrc[3] * w;
146 w = sinc(-1.0 - fract) * _kaiser8[2];
147 out0 += psrc[4] * w; out1 += psrc[5] * w;
148 w = _kaiser8[3] * ((fract < 1e-5) ? 1.0 : sinc(- fract)); // sinc(0) = 1
149 out0 += psrc[6] * w; out1 += psrc[7] * w;
150 w = sinc( 1.0 - fract) * _kaiser8[4];
151 out0 += psrc[8] * w; out1 += psrc[9] * w;
152 w = sinc( 2.0 - fract) * _kaiser8[5];
153 out0 += psrc[10] * w; out1 += psrc[11] * w;
154 w = sinc( 3.0 - fract) * _kaiser8[6];
155 out0 += psrc[12] * w; out1 += psrc[13] * w;
156 w = sinc( 4.0 - fract) * _kaiser8[7];
157 out0 += psrc[14] * w; out1 += psrc[15] * w;
159 pdest[2*i] = (SAMPLETYPE)out0;
160 pdest[2*i+1] = (SAMPLETYPE)out1;
161 i ++;
163 // update position fraction
164 fract += rate;
165 // update whole positions
166 int whole = (int)fract;
167 fract -= whole;
168 psrc += 2*whole;
169 srcCount += whole;
170 }
171 srcSamples = srcCount;
172 return i;
173 }
176 /// Transpose stereo audio. Returns number of produced output samples, and
177 /// updates "srcSamples" to amount of consumed source samples
178 int InterpolateShannon::transposeMulti(SAMPLETYPE *pdest,
179 const SAMPLETYPE *psrc,
180 int &srcSamples)
181 {
182 // not implemented
183 assert(false);
184 return 0;
185 }
