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120 lines
4.3 KiB
C
120 lines
4.3 KiB
C
/*
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* LSP computing for ACELP-based codecs
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*
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* Copyright (c) 2008 Vladimir Voroshilov
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVCODEC_LSP_H
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#define AVCODEC_LSP_H
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#include <stdint.h>
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/**
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(I.F) means fixed-point value with F fractional and I integer bits
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*/
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/**
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* \brief ensure a minimum distance between LSFs
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* \param lsfq [in/out] LSF to check and adjust
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* \param lsfq_min_distance minimum distance between LSFs
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* \param lsfq_min minimum allowed LSF value
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* \param lsfq_max maximum allowed LSF value
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* \param lp_order LP filter order
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*/
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void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max, int lp_order);
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/**
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* Adjust the quantized LSFs so they are increasing and not too close.
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*
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* This step is not mentioned in the AMR spec but is in the reference C decoder.
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* Omitting this step creates audible distortion on the sinusoidal sweep
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* test vectors in 3GPP TS 26.074.
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*
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* @param[in,out] lsf LSFs in Hertz
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* @param min_spacing minimum distance between two consecutive lsf values
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* @param size size of the lsf vector
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*/
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void ff_set_min_dist_lsf(float *lsf, double min_spacing, int order);
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/**
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* \brief Convert LSF to LSP
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* \param lsp [out] LSP coefficients (-0x8000 <= (0.15) < 0x8000)
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* \param lsf normalized LSF coefficients (0 <= (2.13) < 0x2000 * PI)
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* \param lp_order LP filter order
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*
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* \remark It is safe to pass the same array into the lsf and lsp parameters.
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*/
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void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order);
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/**
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* \brief LSP to LP conversion (3.2.6 of G.729)
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* \param lp [out] decoded LP coefficients (-0x8000 <= (3.12) < 0x8000)
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* \param lsp LSP coefficients (-0x8000 <= (0.15) < 0x8000)
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* \param lp_half_order LP filter order, divided by 2
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*/
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void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order);
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/**
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* \brief Interpolate LSP for the first subframe and convert LSP -> LP for both subframes (3.2.5 and 3.2.6 of G.729)
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* \param lp_1st [out] decoded LP coefficients for first subframe (-0x8000 <= (3.12) < 0x8000)
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* \param lp_2nd [out] decoded LP coefficients for second subframe (-0x8000 <= (3.12) < 0x8000)
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* \param lsp_2nd LSP coefficients of the second subframe (-0x8000 <= (0.15) < 0x8000)
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* \param lsp_prev LSP coefficients from the second subframe of the previous frame (-0x8000 <= (0.15) < 0x8000)
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* \param lp_order LP filter order
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*/
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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);
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#define MAX_LP_HALF_ORDER 8
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/**
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* Reconstructs LPC coefficients from the line spectral pair frequencies.
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*
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* @param lsp line spectral pairs in cosine domain
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* @param lpc linear predictive coding coefficients
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* @param lp_half_order half the number of the amount of LPCs to be
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* reconstructed, need to be smaller or equal to MAX_LP_HALF_ORDER
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*
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* @note buffers should have a minimux size of 2*lp_half_order elements.
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*
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* TIA/EIA/IS-733 2.4.3.3.5
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*/
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void ff_acelp_lspd2lpc(const double *lsp, float *lpc, int lp_half_order);
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/**
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* Sort values in ascending order.
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*
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* @note O(n) if data already sorted, O(n^2) - otherwise
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*/
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void ff_sort_nearly_sorted_floats(float *vals, int len);
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/**
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* Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients
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* needed for LSP to LPC conversion.
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* We only need to calculate the 6 first elements of the polynomial.
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*
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* @param lsp line spectral pairs in cosine domain
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* @param f [out] polynomial input/output as a vector
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*
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* TIA/EIA/IS-733 2.4.3.3.5-1/2
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*/
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void ff_lsp2polyf(const double *lsp, double *f, int lp_half_order);
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#endif /* AVCODEC_LSP_H */
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