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 lsfq [in/out] 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 */
40void 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 */
53void ff_set_min_dist_lsf(float *lsf, double min_spacing, int order);
54
55/**
56 * \brief Convert LSF to LSP
57 * \param lsp [out] 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 */
63void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order);
64
65/**
66 * \brief LSP to LP conversion (3.2.6 of G.729)
67 * \param lp [out] decoded LP coefficients (-0x8000 <= (3.12) < 0x8000)
68 * \param lsp LSP coefficients (-0x8000 <= (0.15) < 0x8000)
69 * \param lp_half_order LP filter order, divided by 2
70 */
71void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order);
72
73/**
74 * \brief Interpolate LSP for the first subframe and convert LSP -> LP for both subframes (3.2.5 and 3.2.6 of G.729)
75 * \param lp_1st [out] decoded LP coefficients for first subframe (-0x8000 <= (3.12) < 0x8000)
76 * \param lp_2nd [out] decoded LP coefficients for second subframe (-0x8000 <= (3.12) < 0x8000)
77 * \param lsp_2nd LSP coefficients of the second subframe (-0x8000 <= (0.15) < 0x8000)
78 * \param lsp_prev LSP coefficients from the second subframe of the previous frame (-0x8000 <= (0.15) < 0x8000)
79 * \param lp_order LP filter order
80 */
81void 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);
82
83
84#define MAX_LP_HALF_ORDER 8
85
86/**
87 * Reconstructs LPC coefficients from the line spectral pair frequencies.
88 *
89 * @param lsp line spectral pairs in cosine domain
90 * @param lpc linear predictive coding coefficients
91 * @param lp_half_order half the number of the amount of LPCs to be
92 *        reconstructed, need to be smaller or equal to MAX_LP_HALF_ORDER
93 *
94 * @note buffers should have a minimux size of 2*lp_half_order elements.
95 *
96 * TIA/EIA/IS-733 2.4.3.3.5
97 */
98void ff_acelp_lspd2lpc(const double *lsp, float *lpc, int lp_half_order);
99
100/**
101 * Sort values in ascending order.
102 *
103 * @note O(n) if data already sorted, O(n^2) - otherwise
104 */
105void ff_sort_nearly_sorted_floats(float *vals, int len);
106
107/**
108 * Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients
109 * needed for LSP to LPC conversion.
110 * We only need to calculate the 6 first elements of the polynomial.
111 *
112 * @param lsp line spectral pairs in cosine domain
113 * @param f [out] polynomial input/output as a vector
114 *
115 * TIA/EIA/IS-733 2.4.3.3.5-1/2
116 */
117void ff_lsp2polyf(const double *lsp, double *f, int lp_half_order);
118
119#endif /* AVCODEC_LSP_H */
120