ac3dsp.c
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1 /*
2  * AC-3 DSP utils
3  * Copyright (c) 2011 Justin Ruggles
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "libavutil/avassert.h"
23 #include "avcodec.h"
24 #include "ac3.h"
25 #include "ac3dsp.h"
26 
27 static void ac3_exponent_min_c(uint8_t *exp, int num_reuse_blocks, int nb_coefs)
28 {
29  int blk, i;
30 
31  if (!num_reuse_blocks)
32  return;
33 
34  for (i = 0; i < nb_coefs; i++) {
35  uint8_t min_exp = *exp;
36  uint8_t *exp1 = exp + 256;
37  for (blk = 0; blk < num_reuse_blocks; blk++) {
38  uint8_t next_exp = *exp1;
39  if (next_exp < min_exp)
40  min_exp = next_exp;
41  exp1 += 256;
42  }
43  *exp++ = min_exp;
44  }
45 }
46 
47 static int ac3_max_msb_abs_int16_c(const int16_t *src, int len)
48 {
49  int i, v = 0;
50  for (i = 0; i < len; i++)
51  v |= abs(src[i]);
52  return v;
53 }
54 
55 static void ac3_lshift_int16_c(int16_t *src, unsigned int len,
56  unsigned int shift)
57 {
58  uint32_t *src32 = (uint32_t *)src;
59  const uint32_t mask = ~(((1 << shift) - 1) << 16);
60  int i;
61  len >>= 1;
62  for (i = 0; i < len; i += 8) {
63  src32[i ] = (src32[i ] << shift) & mask;
64  src32[i+1] = (src32[i+1] << shift) & mask;
65  src32[i+2] = (src32[i+2] << shift) & mask;
66  src32[i+3] = (src32[i+3] << shift) & mask;
67  src32[i+4] = (src32[i+4] << shift) & mask;
68  src32[i+5] = (src32[i+5] << shift) & mask;
69  src32[i+6] = (src32[i+6] << shift) & mask;
70  src32[i+7] = (src32[i+7] << shift) & mask;
71  }
72 }
73 
74 static void ac3_rshift_int32_c(int32_t *src, unsigned int len,
75  unsigned int shift)
76 {
77  do {
78  *src++ >>= shift;
79  *src++ >>= shift;
80  *src++ >>= shift;
81  *src++ >>= shift;
82  *src++ >>= shift;
83  *src++ >>= shift;
84  *src++ >>= shift;
85  *src++ >>= shift;
86  len -= 8;
87  } while (len > 0);
88 }
89 
90 static void float_to_fixed24_c(int32_t *dst, const float *src, unsigned int len)
91 {
92  const float scale = 1 << 24;
93  do {
94  *dst++ = lrintf(*src++ * scale);
95  *dst++ = lrintf(*src++ * scale);
96  *dst++ = lrintf(*src++ * scale);
97  *dst++ = lrintf(*src++ * scale);
98  *dst++ = lrintf(*src++ * scale);
99  *dst++ = lrintf(*src++ * scale);
100  *dst++ = lrintf(*src++ * scale);
101  *dst++ = lrintf(*src++ * scale);
102  len -= 8;
103  } while (len > 0);
104 }
105 
106 static void ac3_bit_alloc_calc_bap_c(int16_t *mask, int16_t *psd,
107  int start, int end,
108  int snr_offset, int floor,
109  const uint8_t *bap_tab, uint8_t *bap)
110 {
111  int bin, band, band_end;
112 
113  /* special case, if snr offset is -960, set all bap's to zero */
114  if (snr_offset == -960) {
115  memset(bap, 0, AC3_MAX_COEFS);
116  return;
117  }
118 
119  bin = start;
120  band = ff_ac3_bin_to_band_tab[start];
121  do {
122  int m = (FFMAX(mask[band] - snr_offset - floor, 0) & 0x1FE0) + floor;
123  band_end = ff_ac3_band_start_tab[++band];
124  band_end = FFMIN(band_end, end);
125 
126  for (; bin < band_end; bin++) {
127  int address = av_clip((psd[bin] - m) >> 5, 0, 63);
128  bap[bin] = bap_tab[address];
129  }
130  } while (end > band_end);
131 }
132 
133 static void ac3_update_bap_counts_c(uint16_t mant_cnt[16], uint8_t *bap,
134  int len)
135 {
136  while (len-- > 0)
137  mant_cnt[bap[len]]++;
138 }
139 
140 DECLARE_ALIGNED(16, const uint16_t, ff_ac3_bap_bits)[16] = {
141  0, 0, 0, 3, 0, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
142 };
143 
144 static int ac3_compute_mantissa_size_c(uint16_t mant_cnt[6][16])
145 {
146  int blk, bap;
147  int bits = 0;
148 
149  for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
150  // bap=1 : 3 mantissas in 5 bits
151  bits += (mant_cnt[blk][1] / 3) * 5;
152  // bap=2 : 3 mantissas in 7 bits
153  // bap=4 : 2 mantissas in 7 bits
154  bits += ((mant_cnt[blk][2] / 3) + (mant_cnt[blk][4] >> 1)) * 7;
155  // bap=3 : 1 mantissa in 3 bits
156  bits += mant_cnt[blk][3] * 3;
157  // bap=5 to 15 : get bits per mantissa from table
158  for (bap = 5; bap < 16; bap++)
159  bits += mant_cnt[blk][bap] * ff_ac3_bap_bits[bap];
160  }
161  return bits;
162 }
163 
164 static void ac3_extract_exponents_c(uint8_t *exp, int32_t *coef, int nb_coefs)
165 {
166  int i;
167 
168  for (i = 0; i < nb_coefs; i++) {
169  int v = abs(coef[i]);
170  exp[i] = v ? 23 - av_log2(v) : 24;
171  }
172 }
173 
174 av_cold void ff_ac3dsp_init(AC3DSPContext *c, int bit_exact)
175 {
185 
186  if (ARCH_ARM)
187  ff_ac3dsp_init_arm(c, bit_exact);
188  if (HAVE_MMX)
189  ff_ac3dsp_init_x86(c, bit_exact);
190 }