xref: /third_party/ffmpeg/libavcodec/atrac.c (revision cabdff1a) 
1/*
2 * common functions for the ATRAC family of decoders
3 *
4 * Copyright (c) 2006-2013 Maxim Poliakovski
5 * Copyright (c) 2006-2008 Benjamin Larsson
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24/**
25 * @file
26 */
27
28#include <math.h>
29#include <string.h>
30
31#include "libavutil/attributes.h"
32#include "libavutil/thread.h"
33
34#include "atrac.h"
35
36float ff_atrac_sf_table[64];
37static float qmf_window[48];
38
39static const float qmf_48tap_half[24] = {
40   -0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
41    0.0002422519,  -0.00085293897,-0.0005205574,  0.0020340169,
42    0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
43   -0.000061169922,-0.01344162,    0.0024626821,  0.021736089,
44   -0.007801671,   -0.034090221,   0.01880949,    0.054326009,
45   -0.043596379,   -0.099384367,   0.13207909,    0.46424159
46};
47
48static av_cold void atrac_generate_tables(void)
49{
50    /* Generate scale factors */
51    for (int i = 0; i < 64; i++)
52        ff_atrac_sf_table[i] = pow(2.0, (i - 15) / 3.0);
53
54    /* Generate the QMF window. */
55    for (int i = 0; i < 24; i++) {
56        float s = qmf_48tap_half[i] * 2.0;
57        qmf_window[i] = qmf_window[47 - i] = s;
58    }
59}
60
61av_cold void ff_atrac_generate_tables(void)
62{
63    static AVOnce init_static_once = AV_ONCE_INIT;
64    ff_thread_once(&init_static_once, atrac_generate_tables);
65}
66
67av_cold void ff_atrac_init_gain_compensation(AtracGCContext *gctx, int id2exp_offset,
68                                             int loc_scale)
69{
70    int i;
71
72    gctx->loc_scale     = loc_scale;
73    gctx->loc_size      = 1 << loc_scale;
74    gctx->id2exp_offset = id2exp_offset;
75
76    /* Generate gain level table. */
77    for (i = 0; i < 16; i++)
78        gctx->gain_tab1[i] = powf(2.0, id2exp_offset - i);
79
80    /* Generate gain interpolation table. */
81    for (i = -15; i < 16; i++)
82        gctx->gain_tab2[i + 15] = powf(2.0, -1.0f / gctx->loc_size * i);
83}
84
85void ff_atrac_gain_compensation(AtracGCContext *gctx, float *in, float *prev,
86                                AtracGainInfo *gc_now, AtracGainInfo *gc_next,
87                                int num_samples, float *out)
88{
89    float lev, gc_scale, gain_inc;
90    int i, pos, lastpos;
91
92    gc_scale = gc_next->num_points ? gctx->gain_tab1[gc_next->lev_code[0]]
93                                   : 1.0f;
94
95    if (!gc_now->num_points) {
96        for (pos = 0; pos < num_samples; pos++)
97            out[pos] = in[pos] * gc_scale + prev[pos];
98    } else {
99        pos = 0;
100
101        for (i = 0; i < gc_now->num_points; i++) {
102            lastpos = gc_now->loc_code[i] << gctx->loc_scale;
103
104            lev = gctx->gain_tab1[gc_now->lev_code[i]];
105            gain_inc = gctx->gain_tab2[(i + 1 < gc_now->num_points ? gc_now->lev_code[i + 1]
106                                                                   : gctx->id2exp_offset) -
107                                       gc_now->lev_code[i] + 15];
108
109            /* apply constant gain level and overlap */
110            for (; pos < lastpos; pos++)
111                out[pos] = (in[pos] * gc_scale + prev[pos]) * lev;
112
113            /* interpolate between two different gain levels */
114            for (; pos < lastpos + gctx->loc_size; pos++) {
115                out[pos] = (in[pos] * gc_scale + prev[pos]) * lev;
116                lev *= gain_inc;
117            }
118        }
119
120        for (; pos < num_samples; pos++)
121            out[pos] = in[pos] * gc_scale + prev[pos];
122    }
123
124    /* copy the overlapping part into the delay buffer */
125    memcpy(prev, &in[num_samples], num_samples * sizeof(float));
126}
127
128void ff_atrac_iqmf(float *inlo, float *inhi, unsigned int nIn, float *pOut,
129                   float *delayBuf, float *temp)
130{
131    int   i, j;
132    float   *p1, *p3;
133
134    memcpy(temp, delayBuf, 46*sizeof(float));
135
136    p3 = temp + 46;
137
138    /* loop1 */
139    for(i=0; i<nIn; i+=2){
140        p3[2*i+0] = inlo[i  ] + inhi[i  ];
141        p3[2*i+1] = inlo[i  ] - inhi[i  ];
142        p3[2*i+2] = inlo[i+1] + inhi[i+1];
143        p3[2*i+3] = inlo[i+1] - inhi[i+1];
144    }
145
146    /* loop2 */
147    p1 = temp;
148    for (j = nIn; j != 0; j--) {
149        float s1 = 0.0;
150        float s2 = 0.0;
151
152        for (i = 0; i < 48; i += 2) {
153            s1 += p1[i] * qmf_window[i];
154            s2 += p1[i+1] * qmf_window[i+1];
155        }
156
157        pOut[0] = s2;
158        pOut[1] = s1;
159
160        p1 += 2;
161        pOut += 2;
162    }
163
164    /* Update the delay buffer. */
165    memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
166}
167