b5b9add7f2346ca523137521945936ab59bb2c9b
[libav.git] / libavcodec / acelp_pitch_delay.h
1 /*
2 * gain code, gain pitch and pitch delay decoding
3 *
4 * Copyright (c) 2008 Vladimir Voroshilov
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 #ifndef FFMPEG_ACELP_PITCH_DELAY_H
24 #define FFMPEG_ACELP_PITCH_DELAY_H
25
26 #include <stdint.h>
27
28 #define PITCH_DELAY_MIN 20
29 #define PITCH_DELAY_MAX 143
30
31 /**
32 * \brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3
33 * resolution.
34 * \param ac_index adaptive codebook index (8 bits)
35 *
36 * \return pitch delay in 1/3 units
37 *
38 * Pitch delay is coded:
39 * with 1/3 resolution, 19 < pitch_delay < 85
40 * integers only, 85 <= pitch_delay <= 143
41 */
42 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index);
43
44 /**
45 * \brief Decode pitch delay of the second subframe encoded by 5 or 6 bits
46 * with 1/3 precision.
47 * \param ac_index adaptive codebook index (5 or 6 bits)
48 * \param pitch_delay_min lower bound (integer) of pitch delay interval
49 * for second subframe
50 *
51 * \return pitch delay in 1/3 units
52 *
53 * Pitch delay is coded:
54 * with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
55 *
56 * \remark The routine is used in G.729 @8k, AMR @10.2k, AMR @7.95k,
57 * AMR @7.4k for the second subframe.
58 */
59 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
60 int ac_index,
61 int pitch_delay_min);
62
63 /**
64 * \brief Decode pitch delay with 1/3 precision.
65 * \param ac_index adaptive codebook index (4 bits)
66 * \param pitch_delay_min lower bound (integer) of pitch delay interval for
67 * second subframe
68 *
69 * \return pitch delay in 1/3 units
70 *
71 * Pitch delay is coded:
72 * integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2
73 * with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1
74 * integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5
75 *
76 * \remark The routine is used in G.729 @6.4k, AMR @6.7k, AMR @5.9k,
77 * AMR @5.15k, AMR @4.75k for the second subframe.
78 */
79 int ff_acelp_decode_4bit_to_2nd_delay3(
80 int ac_index,
81 int pitch_delay_min);
82
83 /**
84 * \brief Decode pitch delay of the first subframe encoded by 9 bits
85 * with 1/6 precision.
86 * \param ac_index adaptive codebook index (9 bits)
87 * \param pitch_delay_min lower bound (integer) of pitch delay interval for
88 * second subframe
89 *
90 * \return pitch delay in 1/6 units
91 *
92 * Pitch delay is coded:
93 * with 1/6 resolution, 17 < pitch_delay < 95
94 * integers only, 95 <= pitch_delay <= 143
95 *
96 * \remark The routine is used in AMR @12.2k for the first and third subframes.
97 */
98 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index);
99
100 /**
101 * \brief Decode pitch delay of the second subframe encoded by 6 bits
102 * with 1/6 precision.
103 * \param ac_index adaptive codebook index (6 bits)
104 * \param pitch_delay_min lower bound (integer) of pitch delay interval for
105 * second subframe
106 *
107 * \return pitch delay in 1/6 units
108 *
109 * Pitch delay is coded:
110 * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
111 *
112 * \remark The routine is used in AMR @12.2k for the second and fourth subframes.
113 */
114 int ff_acelp_decode_6bit_to_2nd_delay6(
115 int ac_index,
116 int pitch_delay_min);
117
118 /**
119 * \brief Update past quantized energies
120 * \param quant_energy [in/out] past quantized energies (5.10)
121 * \param gain_corr_factor gain correction factor
122 * \param log2_ma_pred_order log2() of MA prediction order
123 * \param erasure frame erasure flag
124 *
125 * If frame erasure flag is not equal to zero, memory is updated with
126 * averaged energy, attenuated by 4dB:
127 * max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order
128 *
129 * In normal mode memory is updated with
130 * Er - Ep = 20 * log10(gain_corr_factor)
131 *
132 * \remark The routine is used in G.729 and AMR (all modes).
133 */
134 void ff_acelp_update_past_gain(
135 int16_t* quant_energy,
136 int gain_corr_factor,
137 int log2_ma_pred_order,
138 int erasure);
139
140 /**
141 * \brief Decode the adaptive codebook gain and add
142 * correction (4.1.5 and 3.9.1 of G.729).
143 * \param gain_corr_factor gain correction factor (2.13)
144 * \param fc_v fixed-codebook vector (2.13)
145 * \param mr_energy mean innovation energy and fixed-point correction (7.13)
146 * \param quant_energy [in/out] past quantized energies (5.10)
147 * \param subframe_size length of subframe
148 * \param ma_pred_order MA prediction order
149 *
150 * \return quantized fixed-codebook gain (14.1)
151 *
152 * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)
153 *
154 * Em - mean innovation energy (dB, constant, depends on decoding algorithm)
155 * Ep - mean-removed predicted energy (dB)
156 * Er - mean-removed innovation energy (dB)
157 * Ei - mean energy of the fixed-codebook contribution (dB)
158 * N - subframe_size
159 * M - MA (Moving Average) prediction order
160 * gc - fixed-codebook gain
161 * gc_p - predicted fixed-codebook gain
162 *
163 * Fixed codebook gain is computed using predicted gain gc_p and
164 * correction factor gain_corr_factor as shown below:
165 *
166 * gc = gc_p * gain_corr_factor
167 *
168 * The predicted fixed codebook gain gc_p is found by predicting
169 * the energy of the fixed-codebook contribution from the energy
170 * of previous fixed-codebook contributions.
171 *
172 * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }
173 *
174 * Ei = 10log(mean)
175 *
176 * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em
177 *
178 * Replacing Er with Ep and gc with gc_p we will receive:
179 *
180 * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em
181 *
182 * and from above:
183 *
184 * gc_p = 10^((Ep - Ei + Em) / 20)
185 *
186 * Ep is predicted using past energies and prediction coefficients:
187 *
188 * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }
189 *
190 * gc_p in fixed-point arithmetic is calculated as following:
191 *
192 * mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } =
193 * = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26
194 *
195 * Ei = 10log(mean) = -10log(N) - 10log(2^26) +
196 * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
197 *
198 * Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) -
199 * - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) =
200 * = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
201 *
202 * gc_p = 10 ^ ((Ep - Ei + Em) / 20) =
203 * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))
204 *
205 * where
206 *
207 * mr_energy = Em + 10log(N) + 10log(2^26)
208 *
209 * \remark The routine is used in G.729 and AMR (all modes).
210 */
211 int16_t ff_acelp_decode_gain_code(
212 int gain_corr_factor,
213 const int16_t* fc_v,
214 int mr_energy,
215 const int16_t* quant_energy,
216 const int16_t* ma_prediction_coeff,
217 int subframe_size,
218 int max_pred_order);
219
220 #endif /* FFMPEG_ACELP_PITCH_DELAY_H */