ffmpeg / libavcodec / lpc.h @ 77a78e9b
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/**


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* LPC utility code

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* Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>

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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 021101301 USA

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*/

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#ifndef AVCODEC_LPC_H

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#define AVCODEC_LPC_H

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#include <stdint.h> 
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#include "dsputil.h" 
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#define ORDER_METHOD_EST 0 
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#define ORDER_METHOD_2LEVEL 1 
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#define ORDER_METHOD_4LEVEL 2 
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#define ORDER_METHOD_8LEVEL 3 
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#define ORDER_METHOD_SEARCH 4 
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#define ORDER_METHOD_LOG 5 
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#define MIN_LPC_ORDER 1 
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#define MAX_LPC_ORDER 32 
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typedef struct LPCContext { 
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int blocksize;

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int max_order;

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enum AVLPCType lpc_type;

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double *windowed_samples;

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/**

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* Apply a Welch window to an array of input samples.

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* The output samples have the same scale as the input, but are in double

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* sample format.

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* @param data input samples

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* @param len number of input samples

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* @param w_data output samples

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*/

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void (*lpc_apply_welch_window)(const int32_t *data, int len, 
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double *w_data);

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/**

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* Perform autocorrelation on input samples with delay of 0 to lag.

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* @param data input samples.

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* constraints: no alignment needed, but must have have at

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* least lag*sizeof(double) valid bytes preceeding it, and

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* size must be at least (len+1)*sizeof(double) if data is

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* 16byte aligned or (len+2)*sizeof(double) if data is

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* unaligned.

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* @param len number of input samples to process

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* @param lag maximum delay to calculate

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* @param autoc output autocorrelation coefficients.

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* constraints: array size must be at least lag+1.

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*/

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void (*lpc_compute_autocorr)(const double *data, int len, int lag, 
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double *autoc);

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} LPCContext; 
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/**

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* Calculate LPC coefficients for multiple orders

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*/

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int ff_lpc_calc_coefs(LPCContext *s,

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const int32_t *samples, int blocksize, int min_order, 
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int max_order, int precision, 
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int32_t coefs[][MAX_LPC_ORDER], int *shift,

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enum AVLPCType lpc_type, int lpc_passes, 
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int omethod, int max_shift, int zero_shift); 
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/**

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* Initialize LPCContext.

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*/

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int ff_lpc_init(LPCContext *s, int blocksize, int max_order, 
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enum AVLPCType lpc_type);

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void ff_lpc_init_x86(LPCContext *s);

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/**

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* Uninitialize LPCContext.

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*/

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void ff_lpc_end(LPCContext *s);

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#ifdef LPC_USE_DOUBLE

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#define LPC_TYPE double 
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#else

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#define LPC_TYPE float 
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#endif

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/**

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* LevinsonDurbin recursion.

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* Produce LPC coefficients from autocorrelation data.

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*/

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static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order, 
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LPC_TYPE *lpc, int lpc_stride, int fail, 
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int normalize)

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{ 
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int i, j;

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LPC_TYPE err; 
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LPC_TYPE *lpc_last = lpc; 
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if (normalize)

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err = *autoc++; 
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if (fail && (autoc[max_order  1] == 0  err <= 0)) 
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return 1; 
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for(i=0; i<max_order; i++) { 
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LPC_TYPE r = autoc[i]; 
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if (normalize) {

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for(j=0; j<i; j++) 
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r = lpc_last[j] * autoc[ij1];

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r /= err; 
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err *= 1.0  (r * r); 
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} 
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lpc[i] = r; 
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for(j=0; j < (i+1)>>1; j++) { 
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LPC_TYPE f = lpc_last[ j]; 
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LPC_TYPE b = lpc_last[i1j];

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lpc[ j] = f + r * b; 
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lpc[i1j] = b + r * f;

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} 
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if (fail && err < 0) 
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return 1; 
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lpc_last = lpc; 
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lpc += lpc_stride; 
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} 
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return 0; 
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} 
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#endif /* AVCODEC_LPC_H */ 