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atrac.c
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1 /*
2  * Atrac common functions
3  * Copyright (c) 2006-2008 Maxim Poliakovski
4  * Copyright (c) 2006-2008 Benjamin Larsson
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /**
24  * @file
25  */
26 
27 #include <math.h>
28 #include <stddef.h>
29 #include <stdio.h>
30 #include <string.h>
31 
32 #include "avcodec.h"
33 #include "atrac.h"
34 
36 static float qmf_window[48];
37 
38 static const float qmf_48tap_half[24] = {
39  -0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
40  0.0002422519, -0.00085293897,-0.0005205574, 0.0020340169,
41  0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
42  -0.000061169922,-0.01344162, 0.0024626821, 0.021736089,
43  -0.007801671, -0.034090221, 0.01880949, 0.054326009,
44  -0.043596379, -0.099384367, 0.13207909, 0.46424159
45 };
46 
47 /**
48  * Generate common tables
49  */
50 
52 {
53  int i;
54  float s;
55 
56  /* Generate scale factors */
57  if (!ff_atrac_sf_table[63])
58  for (i=0 ; i<64 ; i++)
59  ff_atrac_sf_table[i] = pow(2.0, (i - 15) / 3.0);
60 
61  /* Generate the QMF window. */
62  if (!qmf_window[47])
63  for (i=0 ; i<24; i++) {
64  s = qmf_48tap_half[i] * 2.0;
65  qmf_window[i] = qmf_window[47 - i] = s;
66  }
67 }
68 
69 
70 /**
71  * Quadrature mirror synthesis filter.
72  *
73  * @param inlo lower part of spectrum
74  * @param inhi higher part of spectrum
75  * @param nIn size of spectrum buffer
76  * @param pOut out buffer
77  * @param delayBuf delayBuf buffer
78  * @param temp temp buffer
79  */
80 
81 
82 void ff_atrac_iqmf (float *inlo, float *inhi, unsigned int nIn, float *pOut, float *delayBuf, float *temp)
83 {
84  int i, j;
85  float *p1, *p3;
86 
87  memcpy(temp, delayBuf, 46*sizeof(float));
88 
89  p3 = temp + 46;
90 
91  /* loop1 */
92  for(i=0; i<nIn; i+=2){
93  p3[2*i+0] = inlo[i ] + inhi[i ];
94  p3[2*i+1] = inlo[i ] - inhi[i ];
95  p3[2*i+2] = inlo[i+1] + inhi[i+1];
96  p3[2*i+3] = inlo[i+1] - inhi[i+1];
97  }
98 
99  /* loop2 */
100  p1 = temp;
101  for (j = nIn; j != 0; j--) {
102  float s1 = 0.0;
103  float s2 = 0.0;
104 
105  for (i = 0; i < 48; i += 2) {
106  s1 += p1[i] * qmf_window[i];
107  s2 += p1[i+1] * qmf_window[i+1];
108  }
109 
110  pOut[0] = s2;
111  pOut[1] = s1;
112 
113  p1 += 2;
114  pOut += 2;
115  }
116 
117  /* Update the delay buffer. */
118  memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
119 }