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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 */
  131.