0,0 → 1,197 |
/* |
* 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 "libavutil/avassert.h" |
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#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 |
|
/** |
* LPC analysis type |
*/ |
enum FFLPCType { |
FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type |
FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients |
FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients |
FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion |
FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization |
FF_LPC_TYPE_NB , ///< Not part of ABI |
}; |
|
typedef struct LPCContext { |
int blocksize; |
int max_order; |
enum FFLPCType lpc_type; |
double *windowed_buffer; |
double *windowed_samples; |
|
/** |
* Apply a Welch window to an array of input samples. |
* The output samples have the same scale as the input, but are in double |
* sample format. |
* @param data input samples |
* @param len number of input samples |
* @param w_data output samples |
*/ |
void (*lpc_apply_welch_window)(const int32_t *data, int len, |
double *w_data); |
/** |
* Perform autocorrelation on input samples with delay of 0 to lag. |
* @param data input samples. |
* constraints: no alignment needed, but must have at |
* least lag*sizeof(double) valid bytes preceding it, and |
* size must be at least (len+1)*sizeof(double) if data is |
* 16-byte aligned or (len+2)*sizeof(double) if data is |
* unaligned. |
* @param len number of input samples to process |
* @param lag maximum delay to calculate |
* @param autoc output autocorrelation coefficients. |
* constraints: array size must be at least lag+1. |
*/ |
void (*lpc_compute_autocorr)(const double *data, int len, int lag, |
double *autoc); |
} LPCContext; |
|
|
/** |
* Calculate LPC coefficients for multiple orders |
*/ |
int ff_lpc_calc_coefs(LPCContext *s, |
const int32_t *samples, int blocksize, int min_order, |
int max_order, int precision, |
int32_t coefs[][MAX_LPC_ORDER], int *shift, |
enum FFLPCType lpc_type, int lpc_passes, |
int omethod, int max_shift, int zero_shift); |
|
int ff_lpc_calc_ref_coefs(LPCContext *s, |
const int32_t *samples, int order, double *ref); |
|
/** |
* Initialize LPCContext. |
*/ |
int ff_lpc_init(LPCContext *s, int blocksize, int max_order, |
enum FFLPCType lpc_type); |
void ff_lpc_init_x86(LPCContext *s); |
|
/** |
* Uninitialize LPCContext. |
*/ |
void ff_lpc_end(LPCContext *s); |
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#ifdef LPC_USE_DOUBLE |
#define LPC_TYPE double |
#else |
#define LPC_TYPE float |
#endif |
|
/** |
* Schur recursion. |
* Produces reflection coefficients from autocorrelation data. |
*/ |
static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order, |
LPC_TYPE *ref, LPC_TYPE *error) |
{ |
int i, j; |
LPC_TYPE err; |
LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER]; |
|
for (i = 0; i < max_order; i++) |
gen0[i] = gen1[i] = autoc[i + 1]; |
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err = autoc[0]; |
ref[0] = -gen1[0] / err; |
err += gen1[0] * ref[0]; |
if (error) |
error[0] = err; |
for (i = 1; i < max_order; i++) { |
for (j = 0; j < max_order - i; j++) { |
gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j]; |
gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j]; |
} |
ref[i] = -gen1[0] / err; |
err += gen1[0] * ref[i]; |
if (error) |
error[i] = err; |
} |
} |
|
/** |
* 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; |
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av_assert2(normalize || !fail); |
|
if (normalize) |
err = *autoc++; |
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if (fail && (autoc[max_order - 1] == 0 || err <= 0)) |
return -1; |
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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]; |
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r /= err; |
err *= 1.0 - (r * r); |
} |
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lpc[i] = r; |
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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; |
} |
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if (fail && err < 0) |
return -1; |
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lpc_last = lpc; |
lpc += lpc_stride; |
} |
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return 0; |
} |
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#endif /* AVCODEC_LPC_H */ |