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flacdsp_lpc_template.c
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include <stdint.h>
20 #include "libavutil/avutil.h"
21 #include "mathops.h"
22 
23 #undef FUNC
24 #undef sum_type
25 #undef MUL
26 #undef CLIP
27 #undef FSUF
28 
29 #define FUNC(n) AV_JOIN(n ## _, SAMPLE_SIZE)
30 
31 #if SAMPLE_SIZE == 32
32 # define sum_type int64_t
33 # define MUL(a, b) MUL64(a, b)
34 # define CLIP(x) av_clipl_int32(x)
35 #else
36 # define sum_type int32_t
37 # define MUL(a, b) ((a) * (b))
38 # define CLIP(x) (x)
39 #endif
40 
41 #define LPC1(x) { \
42  int c = coefs[(x)-1]; \
43  p0 += MUL(c, s); \
44  s = smp[i-(x)+1]; \
45  p1 += MUL(c, s); \
46 }
47 
48 static av_always_inline void FUNC(lpc_encode_unrolled)(int32_t *res,
49  const int32_t *smp, int len, int order,
50  const int32_t *coefs, int shift, int big)
51 {
52  int i;
53  for (i = order; i < len; i += 2) {
54  int s = smp[i-order];
55  sum_type p0 = 0, p1 = 0;
56  if (big) {
57  switch (order) {
58  case 32: LPC1(32)
59  case 31: LPC1(31)
60  case 30: LPC1(30)
61  case 29: LPC1(29)
62  case 28: LPC1(28)
63  case 27: LPC1(27)
64  case 26: LPC1(26)
65  case 25: LPC1(25)
66  case 24: LPC1(24)
67  case 23: LPC1(23)
68  case 22: LPC1(22)
69  case 21: LPC1(21)
70  case 20: LPC1(20)
71  case 19: LPC1(19)
72  case 18: LPC1(18)
73  case 17: LPC1(17)
74  case 16: LPC1(16)
75  case 15: LPC1(15)
76  case 14: LPC1(14)
77  case 13: LPC1(13)
78  case 12: LPC1(12)
79  case 11: LPC1(11)
80  case 10: LPC1(10)
81  case 9: LPC1( 9)
82  LPC1( 8)
83  LPC1( 7)
84  LPC1( 6)
85  LPC1( 5)
86  LPC1( 4)
87  LPC1( 3)
88  LPC1( 2)
89  LPC1( 1)
90  }
91  } else {
92  switch (order) {
93  case 8: LPC1( 8)
94  case 7: LPC1( 7)
95  case 6: LPC1( 6)
96  case 5: LPC1( 5)
97  case 4: LPC1( 4)
98  case 3: LPC1( 3)
99  case 2: LPC1( 2)
100  case 1: LPC1( 1)
101  }
102  }
103  res[i ] = smp[i ] - CLIP(p0 >> shift);
104  res[i+1] = smp[i+1] - CLIP(p1 >> shift);
105  }
106 }
107 
108 static void FUNC(flac_lpc_encode_c)(int32_t *res, const int32_t *smp, int len,
109  int order, const int32_t *coefs, int shift)
110 {
111  int i;
112  for (i = 0; i < order; i++)
113  res[i] = smp[i];
114 #if CONFIG_SMALL
115  for (i = order; i < len; i += 2) {
116  int j;
117  int s = smp[i];
118  sum_type p0 = 0, p1 = 0;
119  for (j = 0; j < order; j++) {
120  int c = coefs[j];
121  p1 += MUL(c, s);
122  s = smp[i-j-1];
123  p0 += MUL(c, s);
124  }
125  res[i ] = smp[i ] - CLIP(p0 >> shift);
126  res[i+1] = smp[i+1] - CLIP(p1 >> shift);
127  }
128 #else
129  switch (order) {
130  case 1: FUNC(lpc_encode_unrolled)(res, smp, len, 1, coefs, shift, 0); break;
131  case 2: FUNC(lpc_encode_unrolled)(res, smp, len, 2, coefs, shift, 0); break;
132  case 3: FUNC(lpc_encode_unrolled)(res, smp, len, 3, coefs, shift, 0); break;
133  case 4: FUNC(lpc_encode_unrolled)(res, smp, len, 4, coefs, shift, 0); break;
134  case 5: FUNC(lpc_encode_unrolled)(res, smp, len, 5, coefs, shift, 0); break;
135  case 6: FUNC(lpc_encode_unrolled)(res, smp, len, 6, coefs, shift, 0); break;
136  case 7: FUNC(lpc_encode_unrolled)(res, smp, len, 7, coefs, shift, 0); break;
137  case 8: FUNC(lpc_encode_unrolled)(res, smp, len, 8, coefs, shift, 0); break;
138  default: FUNC(lpc_encode_unrolled)(res, smp, len, order, coefs, shift, 1); break;
139  }
140 #endif
141 }
142 
143 /* Comment for clarity/de-obfuscation.
144  *
145  * for (int i = order; i < len; i++) {
146  * int32_t p = 0;
147  * for (int j = 0; j < order; j++) {
148  * int c = coefs[j];
149  * int s = smp[(i-1)-j];
150  * p += c*s;
151  * }
152  * res[i] = smp[i] - (p >> shift);
153  * }
154  *
155  * The CONFIG_SMALL code above simplifies to this, in the case of SAMPLE_SIZE
156  * not being equal to 32 (at the present time that means for 16-bit audio). The
157  * code above does 2 samples per iteration. Commit bfdd5bc (made all the way
158  * back in 2007) says that way is faster.
159  */
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