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 minimum 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 */ 131