mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-11-26 19:01:44 +02:00
106 lines
2.8 KiB
C
106 lines
2.8 KiB
C
/**
|
|
* LPC utility code
|
|
* Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
|
|
*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* FFmpeg is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
#ifndef AVCODEC_LPC_H
|
|
#define AVCODEC_LPC_H
|
|
|
|
#include <stdint.h>
|
|
#include "dsputil.h"
|
|
|
|
#define ORDER_METHOD_EST 0
|
|
#define ORDER_METHOD_2LEVEL 1
|
|
#define ORDER_METHOD_4LEVEL 2
|
|
#define ORDER_METHOD_8LEVEL 3
|
|
#define ORDER_METHOD_SEARCH 4
|
|
#define ORDER_METHOD_LOG 5
|
|
|
|
#define MIN_LPC_ORDER 1
|
|
#define MAX_LPC_ORDER 32
|
|
|
|
|
|
/**
|
|
* Calculate LPC coefficients for multiple orders
|
|
*/
|
|
int ff_lpc_calc_coefs(DSPContext *s,
|
|
const int32_t *samples, int blocksize, int min_order,
|
|
int max_order, int precision,
|
|
int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc,
|
|
int omethod, int max_shift, int zero_shift);
|
|
|
|
void ff_lpc_compute_autocorr(const int32_t *data, int len, int lag,
|
|
double *autoc);
|
|
|
|
#ifdef LPC_USE_DOUBLE
|
|
#define LPC_TYPE double
|
|
#else
|
|
#define LPC_TYPE float
|
|
#endif
|
|
|
|
/**
|
|
* Levinson-Durbin recursion.
|
|
* Produce LPC coefficients from autocorrelation data.
|
|
*/
|
|
static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
|
|
LPC_TYPE *lpc, int lpc_stride, int fail,
|
|
int normalize)
|
|
{
|
|
int i, j;
|
|
LPC_TYPE err;
|
|
LPC_TYPE *lpc_last = lpc;
|
|
|
|
if (normalize)
|
|
err = *autoc++;
|
|
|
|
if (fail && (autoc[max_order - 1] == 0 || err <= 0))
|
|
return -1;
|
|
|
|
for(i=0; i<max_order; i++) {
|
|
LPC_TYPE r = -autoc[i];
|
|
|
|
if (normalize) {
|
|
for(j=0; j<i; j++)
|
|
r -= lpc_last[j] * autoc[i-j-1];
|
|
|
|
r /= err;
|
|
err *= 1.0 - (r * r);
|
|
}
|
|
|
|
lpc[i] = r;
|
|
|
|
for(j=0; j < (i+1)>>1; j++) {
|
|
LPC_TYPE f = lpc_last[ j];
|
|
LPC_TYPE b = lpc_last[i-1-j];
|
|
lpc[ j] = f + r * b;
|
|
lpc[i-1-j] = b + r * f;
|
|
}
|
|
|
|
if (fail && err < 0)
|
|
return -1;
|
|
|
|
lpc_last = lpc;
|
|
lpc += lpc_stride;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
#endif /* AVCODEC_LPC_H */
|