lpc.h
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1 
22 #ifndef AVCODEC_LPC_H
23 #define AVCODEC_LPC_H
24 
25 #include <stdint.h>
26 #include "dsputil.h"
27 
28 #define ORDER_METHOD_EST 0
29 #define ORDER_METHOD_2LEVEL 1
30 #define ORDER_METHOD_4LEVEL 2
31 #define ORDER_METHOD_8LEVEL 3
32 #define ORDER_METHOD_SEARCH 4
33 #define ORDER_METHOD_LOG 5
34 
35 #define MIN_LPC_ORDER 1
36 #define MAX_LPC_ORDER 32
37 
41 enum FFLPCType {
48 };
49 
50 typedef struct LPCContext {
51  int blocksize;
52  int max_order;
55 
64  void (*lpc_apply_welch_window)(const int32_t *data, int len,
65  double *w_data);
79  void (*lpc_compute_autocorr)(const double *data, int len, int lag,
80  double *autoc);
81 } LPCContext;
82 
83 
88  const int32_t *samples, int blocksize, int min_order,
89  int max_order, int precision,
90  int32_t coefs[][MAX_LPC_ORDER], int *shift,
91  enum FFLPCType lpc_type, int lpc_passes,
92  int omethod, int max_shift, int zero_shift);
93 
97 int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
98  enum FFLPCType lpc_type);
100 
104 void ff_lpc_end(LPCContext *s);
105 
106 #ifdef LPC_USE_DOUBLE
107 #define LPC_TYPE double
108 #else
109 #define LPC_TYPE float
110 #endif
111 
116 static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
117  LPC_TYPE *lpc, int lpc_stride, int fail,
118  int normalize)
119 {
120  int i, j;
121  LPC_TYPE err;
122  LPC_TYPE *lpc_last = lpc;
123 
124  if (normalize)
125  err = *autoc++;
126 
127  if (fail && (autoc[max_order - 1] == 0 || err <= 0))
128  return -1;
129 
130  for(i=0; i<max_order; i++) {
131  LPC_TYPE r = -autoc[i];
132 
133  if (normalize) {
134  for(j=0; j<i; j++)
135  r -= lpc_last[j] * autoc[i-j-1];
136 
137  r /= err;
138  err *= 1.0 - (r * r);
139  }
140 
141  lpc[i] = r;
142 
143  for(j=0; j < (i+1)>>1; j++) {
144  LPC_TYPE f = lpc_last[ j];
145  LPC_TYPE b = lpc_last[i-1-j];
146  lpc[ j] = f + r * b;
147  lpc[i-1-j] = b + r * f;
148  }
149 
150  if (fail && err < 0)
151  return -1;
152 
153  lpc_last = lpc;
154  lpc += lpc_stride;
155  }
156 
157  return 0;
158 }
159 
160 #endif /* AVCODEC_LPC_H */