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1 | /* |
2 | * LSP computing for ACELP-based codecs | |
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 AVCODEC_LSP_H | |
24 | #define AVCODEC_LSP_H | |
25 | ||
26 | #include <stdint.h> | |
27 | ||
28 | /** | |
29 | (I.F) means fixed-point value with F fractional and I integer bits | |
30 | */ | |
31 | ||
32 | /** | |
33 | * @brief ensure a minimum distance between LSFs | |
34 | * @param[in,out] lsfq LSF to check and adjust | |
35 | * @param lsfq_min_distance minimum distance between LSFs | |
36 | * @param lsfq_min minimum allowed LSF value | |
37 | * @param lsfq_max maximum allowed LSF value | |
38 | * @param lp_order LP filter order | |
39 | */ | |
40 | void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max, int lp_order); | |
41 | ||
42 | /** | |
43 | * Adjust the quantized LSFs so they are increasing and not too close. | |
44 | * | |
45 | * This step is not mentioned in the AMR spec but is in the reference C decoder. | |
46 | * Omitting this step creates audible distortion on the sinusoidal sweep | |
47 | * test vectors in 3GPP TS 26.074. | |
48 | * | |
49 | * @param[in,out] lsf LSFs in Hertz | |
50 | * @param min_spacing minimum distance between two consecutive lsf values | |
51 | * @param size size of the lsf vector | |
52 | */ | |
53 | void ff_set_min_dist_lsf(float *lsf, double min_spacing, int size); | |
54 | ||
55 | /** | |
56 | * @brief Convert LSF to LSP | |
57 | * @param[out] lsp LSP coefficients (-0x8000 <= (0.15) < 0x8000) | |
58 | * @param lsf normalized LSF coefficients (0 <= (2.13) < 0x2000 * PI) | |
59 | * @param lp_order LP filter order | |
60 | * | |
61 | * @remark It is safe to pass the same array into the lsf and lsp parameters. | |
62 | */ | |
63 | void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order); | |
64 | ||
65 | /** | |
66 | * Floating point version of ff_acelp_lsf2lsp() | |
67 | */ | |
68 | void ff_acelp_lsf2lspd(double *lsp, const float *lsf, int lp_order); | |
69 | ||
70 | /** | |
71 | * @brief LSP to LP conversion (3.2.6 of G.729) | |
72 | * @param[out] lp decoded LP coefficients (-0x8000 <= (3.12) < 0x8000) | |
73 | * @param lsp LSP coefficients (-0x8000 <= (0.15) < 0x8000) | |
74 | * @param lp_half_order LP filter order, divided by 2 | |
75 | */ | |
76 | void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order); | |
77 | ||
78 | /** | |
79 | * LSP to LP conversion (5.2.4 of AMR-WB) | |
80 | */ | |
81 | void ff_amrwb_lsp2lpc(const double *lsp, float *lp, int lp_order); | |
82 | ||
83 | /** | |
84 | * @brief Interpolate LSP for the first subframe and convert LSP -> LP for both subframes (3.2.5 and 3.2.6 of G.729) | |
85 | * @param[out] lp_1st decoded LP coefficients for first subframe (-0x8000 <= (3.12) < 0x8000) | |
86 | * @param[out] lp_2nd decoded LP coefficients for second subframe (-0x8000 <= (3.12) < 0x8000) | |
87 | * @param lsp_2nd LSP coefficients of the second subframe (-0x8000 <= (0.15) < 0x8000) | |
88 | * @param lsp_prev LSP coefficients from the second subframe of the previous frame (-0x8000 <= (0.15) < 0x8000) | |
89 | * @param lp_order LP filter order | |
90 | */ | |
91 | void ff_acelp_lp_decode(int16_t* lp_1st, int16_t* lp_2nd, const int16_t* lsp_2nd, const int16_t* lsp_prev, int lp_order); | |
92 | ||
93 | ||
94 | #define MAX_LP_HALF_ORDER 10 | |
95 | #define MAX_LP_ORDER (2*MAX_LP_HALF_ORDER) | |
96 | ||
97 | /** | |
98 | * Reconstruct LPC coefficients from the line spectral pair frequencies. | |
99 | * | |
100 | * @param lsp line spectral pairs in cosine domain | |
101 | * @param lpc linear predictive coding coefficients | |
102 | * @param lp_half_order half the number of the amount of LPCs to be | |
103 | * reconstructed, need to be smaller or equal to MAX_LP_HALF_ORDER | |
104 | * | |
105 | * @note buffers should have a minimux size of 2*lp_half_order elements. | |
106 | * | |
107 | * TIA/EIA/IS-733 2.4.3.3.5 | |
108 | */ | |
109 | void ff_acelp_lspd2lpc(const double *lsp, float *lpc, int lp_half_order); | |
110 | ||
111 | /** | |
112 | * Sort values in ascending order. | |
113 | * | |
114 | * @note O(n) if data already sorted, O(n^2) - otherwise | |
115 | */ | |
116 | void ff_sort_nearly_sorted_floats(float *vals, int len); | |
117 | ||
118 | /** | |
119 | * Compute the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients | |
120 | * needed for LSP to LPC conversion. | |
121 | * We only need to calculate the 6 first elements of the polynomial. | |
122 | * | |
123 | * @param lsp line spectral pairs in cosine domain | |
124 | * @param[out] f polynomial input/output as a vector | |
125 | * | |
126 | * TIA/EIA/IS-733 2.4.3.3.5-1/2 | |
127 | */ | |
128 | void ff_lsp2polyf(const double *lsp, double *f, int lp_half_order); | |
129 | ||
130 | #endif /* AVCODEC_LSP_H */ |