1/*
2 * gain code, gain pitch and pitch delay decoding
3 *
4 * Copyright (c) 2008 Vladimir Voroshilov
5 *
6 * This file is part of Libav.
7 *
8 * Libav 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 * Libav 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 Libav; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23#include "libavutil/mathematics.h"
24#include "avcodec.h"
25#include "dsputil.h"
26#include "acelp_pitch_delay.h"
27#include "celp_math.h"
28
29int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
30{
31    ac_index += 58;
32    if(ac_index > 254)
33        ac_index = 3 * ac_index - 510;
34    return ac_index;
35}
36
37int ff_acelp_decode_4bit_to_2nd_delay3(
38        int ac_index,
39        int pitch_delay_min)
40{
41    if(ac_index < 4)
42        return 3 * (ac_index + pitch_delay_min);
43    else if(ac_index < 12)
44        return 3 * pitch_delay_min + ac_index + 6;
45    else
46        return 3 * (ac_index + pitch_delay_min) - 18;
47}
48
49int ff_acelp_decode_5_6_bit_to_2nd_delay3(
50        int ac_index,
51        int pitch_delay_min)
52{
53        return 3 * pitch_delay_min + ac_index - 2;
54}
55
56int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
57{
58    if(ac_index < 463)
59        return ac_index + 105;
60    else
61        return 6 * (ac_index - 368);
62}
63int ff_acelp_decode_6bit_to_2nd_delay6(
64        int ac_index,
65        int pitch_delay_min)
66{
67    return 6 * pitch_delay_min + ac_index - 3;
68}
69
70void ff_acelp_update_past_gain(
71    int16_t* quant_energy,
72    int gain_corr_factor,
73    int log2_ma_pred_order,
74    int erasure)
75{
76    int i;
77    int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
78
79    for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
80    {
81        avg_gain       += quant_energy[i-1];
82        quant_energy[i] = quant_energy[i-1];
83    }
84
85    if(erasure)
86        quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
87    else
88        quant_energy[0] = (6165 * ((ff_log2(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
89}
90
91int16_t ff_acelp_decode_gain_code(
92    DSPContext *dsp,
93    int gain_corr_factor,
94    const int16_t* fc_v,
95    int mr_energy,
96    const int16_t* quant_energy,
97    const int16_t* ma_prediction_coeff,
98    int subframe_size,
99    int ma_pred_order)
100{
101    int i;
102
103    mr_energy <<= 10;
104
105    for(i=0; i<ma_pred_order; i++)
106        mr_energy += quant_energy[i] * ma_prediction_coeff[i];
107
108    mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
109                sqrt(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size, 0));
110    return mr_energy >> 12;
111}
112
113float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
114                            float *prediction_error, float energy_mean,
115                            const float *pred_table)
116{
117    // Equations 66-69:
118    // ^g_c = ^gamma_gc * 100.05 (predicted dB + mean dB - dB of fixed vector)
119    // Note 10^(0.05 * -10log(average x2)) = 1/sqrt((average x2)).
120    float val = fixed_gain_factor *
121        exp2f(M_LOG2_10 * 0.05 *
122              (ff_dot_productf(pred_table, prediction_error, 4) +
123               energy_mean)) /
124        sqrtf(fixed_mean_energy);
125
126    // update quantified prediction error energy history
127    memmove(&prediction_error[0], &prediction_error[1],
128            3 * sizeof(prediction_error[0]));
129    prediction_error[3] = 20.0 * log10f(fixed_gain_factor);
130
131    return val;
132}
133
134void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
135                         const int prev_lag_int, const int subframe,
136                         int third_as_first, int resolution)
137{
138    /* Note n * 10923 >> 15 is floor(x/3) for 0 <= n <= 32767 */
139    if (subframe == 0 || (subframe == 2 && third_as_first)) {
140
141        if (pitch_index < 197)
142            pitch_index += 59;
143        else
144            pitch_index = 3 * pitch_index - 335;
145
146    } else {
147        if (resolution == 4) {
148            int search_range_min = av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
149                                           PITCH_DELAY_MAX - 9);
150
151            // decoding with 4-bit resolution
152            if (pitch_index < 4) {
153                // integer only precision for [search_range_min, search_range_min+3]
154                pitch_index = 3 * (pitch_index + search_range_min) + 1;
155            } else if (pitch_index < 12) {
156                // 1/3 fractional precision for [search_range_min+3 1/3, search_range_min+5 2/3]
157                pitch_index += 3 * search_range_min + 7;
158            } else {
159                // integer only precision for [search_range_min+6, search_range_min+9]
160                pitch_index = 3 * (pitch_index + search_range_min - 6) + 1;
161            }
162        } else {
163            // decoding with 5 or 6 bit resolution, 1/3 fractional precision
164            pitch_index--;
165
166            if (resolution == 5) {
167                pitch_index += 3 * av_clip(prev_lag_int - 10, PITCH_DELAY_MIN,
168                                           PITCH_DELAY_MAX - 19);
169            } else
170                pitch_index += 3 * av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
171                                           PITCH_DELAY_MAX - 9);
172        }
173    }
174    *lag_int  = pitch_index * 10923 >> 15;
175    *lag_frac = pitch_index - 3 * *lag_int - 1;
176}
177