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
31#include "avcodec.h"
32#include "dsputil.h"
33#include "atrac.h"
34
35float sf_table[64];
36float qmf_window[48];
37
38static 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
51void atrac_generate_tables(void)
52{
53    int i;
54    float s;
55
56    /* Generate scale factors */
57    if (!sf_table[63])
58        for (i=0 ; i<64 ; i++)
59            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
82void 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}
120
121