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/libavcodec/lsp.h

http://github.com/FFmpeg/FFmpeg
C Header | 130 lines | 16 code | 16 blank | 98 comment | 0 complexity | 984be4845c0849cf1c0edcb035245e1c MD5 | raw file
  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 */
 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 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 */
 63void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order);
 64
 65/**
 66 * Floating point version of ff_acelp_lsf2lsp()
 67 */
 68void 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 */
 76void 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 */
 81void 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 */
 91void 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 */
109void 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 */
116void 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 */
128void ff_lsp2polyf(const double *lsp, double *f, int lp_half_order);
129
130#endif /* AVCODEC_LSP_H */