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lsp.h
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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 */