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gsmdec_template.c
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1 /*
2  * gsm 06.10 decoder
3  * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * GSM decoder
25  */
26 
27 #include "get_bits.h"
28 #include "gsm.h"
29 #include "gsmdec_data.h"
30 
31 static void apcm_dequant_add(GetBitContext *gb, int16_t *dst)
32 {
33  int i;
34  int maxidx = get_bits(gb, 6);
35  const int16_t *tab = ff_gsm_dequant_tab[maxidx];
36  for (i = 0; i < 13; i++)
37  dst[3*i] += tab[get_bits(gb, 3)];
38 }
39 
40 static inline int gsm_mult(int a, int b)
41 {
42  return (a * b + (1 << 14)) >> 15;
43 }
44 
45 static void long_term_synth(int16_t *dst, int lag, int gain_idx)
46 {
47  int i;
48  const int16_t *src = dst - lag;
49  uint16_t gain = ff_gsm_long_term_gain_tab[gain_idx];
50  for (i = 0; i < 40; i++)
51  dst[i] = gsm_mult(gain, src[i]);
52 }
53 
54 static inline int decode_log_area(int coded, int factor, int offset)
55 {
56  coded <<= 10;
57  coded -= offset;
58  return gsm_mult(coded, factor) << 1;
59 }
60 
61 static av_noinline int get_rrp(int filtered)
62 {
63  int abs = FFABS(filtered);
64  if (abs < 11059) abs <<= 1;
65  else if (abs < 20070) abs += 11059;
66  else abs = (abs >> 2) + 26112;
67  return filtered < 0 ? -abs : abs;
68 }
69 
70 static int filter_value(int in, int rrp[8], int v[9])
71 {
72  int i;
73  for (i = 7; i >= 0; i--) {
74  in -= gsm_mult(rrp[i], v[i]);
75  v[i + 1] = v[i] + gsm_mult(rrp[i], in);
76  }
77  v[0] = in;
78  return in;
79 }
80 
81 static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
82 {
83  int i;
84  int rrp[8];
85  int *lar = ctx->lar[ctx->lar_idx];
86  int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
87  for (i = 0; i < 8; i++)
88  rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
89  for (i = 0; i < 13; i++)
90  dst[i] = filter_value(src[i], rrp, ctx->v);
91 
92  for (i = 0; i < 8; i++)
93  rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar [i] >> 1));
94  for (i = 13; i < 27; i++)
95  dst[i] = filter_value(src[i], rrp, ctx->v);
96 
97  for (i = 0; i < 8; i++)
98  rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar [i] >> 1) + (lar[i] >> 2));
99  for (i = 27; i < 40; i++)
100  dst[i] = filter_value(src[i], rrp, ctx->v);
101 
102  for (i = 0; i < 8; i++)
103  rrp[i] = get_rrp(lar[i]);
104  for (i = 40; i < 160; i++)
105  dst[i] = filter_value(src[i], rrp, ctx->v);
106 
107  ctx->lar_idx ^= 1;
108 }
109 
110 static int postprocess(int16_t *data, int msr)
111 {
112  int i;
113  for (i = 0; i < 160; i++) {
114  msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
115  data[i] = av_clip_int16(msr << 1) & ~7;
116  }
117  return msr;
118 }
119 
120 static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,
121  GetBitContext *gb)
122 {
123  GSMContext *ctx = avctx->priv_data;
124  int i;
125  int16_t *ref_dst = ctx->ref_buf + 120;
126  int *lar = ctx->lar[ctx->lar_idx];
127  lar[0] = decode_log_area(get_bits(gb, 6), 13107, 1 << 15);
128  lar[1] = decode_log_area(get_bits(gb, 6), 13107, 1 << 15);
129  lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
130  lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
131  lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) + 94*2);
132  lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
133  lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) - 341*2);
134  lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
135 
136  for (i = 0; i < 4; i++) {
137  int lag = get_bits(gb, 7);
138  int gain_idx = get_bits(gb, 2);
139  int offset = get_bits(gb, 2);
140  lag = av_clip(lag, 40, 120);
141  long_term_synth(ref_dst, lag, gain_idx);
142  apcm_dequant_add(gb, ref_dst + offset);
143  ref_dst += 40;
144  }
145  memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
146  short_term_synth(ctx, samples, ctx->ref_buf + 120);
147  // for optimal speed this could be merged with short_term_synth,
148  // not done yet because it is a bit ugly
149  ctx->msr = postprocess(samples, ctx->msr);
150  return 0;
151 }