1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
/*
libdemac - A Monkey's Audio decoder
$Id:$
Copyright (C) Dave Chapman 2007
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
*/
#include <inttypes.h>
#include <string.h>
#include "parser.h"
#include "predictor.h"
#include "vector_math32.h"
/* Return 0 if x is zero, -1 if x is positive, 1 if x is negative */
#define SIGN(x) (x) ? (((x) > 0) ? -1 : 1) : 0
static const int32_t initial_coeffs[4] = {
360, 317, -109, 98
};
static void init_predictor(struct predictor_t* p)
{
/* Zero the history buffers */
memset(p->historybuffer, 0, (PREDICTOR_ORDER*4) * sizeof(int32_t));
p->delayA = p->historybuffer + PREDICTOR_ORDER*4;
p->delayB = p->historybuffer + PREDICTOR_ORDER*3;
p->adaptcoeffsA = p->historybuffer + PREDICTOR_ORDER*2;
p->adaptcoeffsB = p->historybuffer + PREDICTOR_ORDER;
/* Initialise and zero the co-efficients */
memcpy(p->coeffsA, initial_coeffs, sizeof(initial_coeffs));
memset(p->coeffsB, 0, sizeof(p->coeffsB));
p->filterA = 0;
p->filterB = 0;
p->lastA = 0;
}
static int do_predictor_decode(struct predictor_t* p, int32_t A, int32_t B)
{
int32_t predictionA, predictionB, currentA;
p->delayA[0] = p->lastA;
p->delayA[-1] = p->delayA[0] - p->delayA[-1];
predictionA = scalarproduct4_rev32(p->coeffsA,p->delayA);
/* Apply a scaled first-order filter compression */
p->delayB[0] = B - ((p->filterB * 31) >> 5);
p->filterB = B;
p->delayB[-1] = p->delayB[0] - p->delayB[-1];
predictionB = scalarproduct5_rev32(p->coeffsB,p->delayB);
currentA = A + ((predictionA + (predictionB >> 1)) >> 10);
p->adaptcoeffsA[0] = SIGN(p->delayA[0]);
p->adaptcoeffsA[-1] = SIGN(p->delayA[-1]);
p->adaptcoeffsB[0] = SIGN(p->delayB[0]);
p->adaptcoeffsB[-1] = SIGN(p->delayB[-1]);
if (A > 0)
{
vector_sub4_rev32(p->coeffsA, p->adaptcoeffsA);
vector_sub5_rev32(p->coeffsB, p->adaptcoeffsB);
}
else if (A < 0)
{
vector_add4_rev32(p->coeffsA, p->adaptcoeffsA);
vector_add5_rev32(p->coeffsB, p->adaptcoeffsB);
}
p->delayA++;
p->delayB++;
p->adaptcoeffsA++;
p->adaptcoeffsB++;
/* Have we filled the history buffer? */
if (p->delayA == p->historybuffer + HISTORY_SIZE + (PREDICTOR_ORDER*4)) {
memmove(p->historybuffer, p->delayA - (PREDICTOR_ORDER*4),
(PREDICTOR_ORDER*4) * sizeof(int32_t));
p->delayA = p->historybuffer + PREDICTOR_ORDER*4;
p->delayB = p->historybuffer + PREDICTOR_ORDER*3;
p->adaptcoeffsA = p->historybuffer + PREDICTOR_ORDER*2;
p->adaptcoeffsB = p->historybuffer + PREDICTOR_ORDER;
}
p->lastA = currentA;
p->filterA = currentA + ((p->filterA * 31) >> 5);
return p->filterA;
}
static int32_t X;
void init_predictor_decoder(struct ape_ctx_t* ape_ctx)
{
X = 0;
init_predictor(&ape_ctx->predictorY);
init_predictor(&ape_ctx->predictorX);
}
int predictor_decode_stereo(struct ape_ctx_t* ape_ctx, int32_t* decoded0, int32_t* decoded1, int count) ICODE_ATTR;
int predictor_decode_stereo(struct ape_ctx_t* ape_ctx, int32_t* decoded0, int32_t* decoded1, int count)
{
while (count--)
{
*decoded0 = do_predictor_decode(&ape_ctx->predictorY, *decoded0, X);
X = do_predictor_decode(&ape_ctx->predictorX, *decoded1, *(decoded0)++);
*(decoded1++) = X;
}
return 0;
}
int predictor_decode_mono(struct ape_ctx_t* ape_ctx, int32_t* decoded0, int count)
{
struct predictor_t* p = &ape_ctx->predictorY;
int32_t predictionA, currentA, A;
currentA = p->lastA;
while (count--)
{
A = *decoded0;
p->delayA[0] = currentA;
p->delayA[-1] = p->delayA[0] - p->delayA[-1];
predictionA = (p->delayA[0] * p->coeffsA[0]) +
(p->delayA[-1] * p->coeffsA[1]) +
(p->delayA[-2] * p->coeffsA[2]) +
(p->delayA[-3] * p->coeffsA[3]);
currentA = A + (predictionA >> 10);
p->adaptcoeffsA[0] = SIGN(p->delayA[0]);
p->adaptcoeffsA[-1] = SIGN(p->delayA[-1]);
if (A > 0)
{
p->coeffsA[0] -= p->adaptcoeffsA[0];
p->coeffsA[1] -= p->adaptcoeffsA[-1];
p->coeffsA[2] -= p->adaptcoeffsA[-2];
p->coeffsA[3] -= p->adaptcoeffsA[-3];
}
else if (A < 0)
{
p->coeffsA[0] += p->adaptcoeffsA[0];
p->coeffsA[1] += p->adaptcoeffsA[-1];
p->coeffsA[2] += p->adaptcoeffsA[-2];
p->coeffsA[3] += p->adaptcoeffsA[-3];
}
p->delayA++;
p->adaptcoeffsA++;
/* Have we filled the history buffer? */
if (p->delayA == p->historybuffer + HISTORY_SIZE + (PREDICTOR_ORDER*4)) {
memmove(p->historybuffer, p->delayA - (PREDICTOR_ORDER*4),
(PREDICTOR_ORDER*4) * sizeof(int32_t));
p->delayA = p->historybuffer + PREDICTOR_ORDER*4;
p->adaptcoeffsA = p->historybuffer + PREDICTOR_ORDER*2;
}
p->filterA = currentA + ((p->filterA * 31) >> 5);
*(decoded0++) = p->filterA;
}
p->lastA = currentA;
return 0;
}
|
