| 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 */ |