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libavcodec/lpc.h

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00001 
00022 #ifndef AVCODEC_LPC_H
00023 #define AVCODEC_LPC_H
00024 
00025 #include <stdint.h>
00026 #include "dsputil.h"
00027 
00028 #define ORDER_METHOD_EST     0
00029 #define ORDER_METHOD_2LEVEL  1
00030 #define ORDER_METHOD_4LEVEL  2
00031 #define ORDER_METHOD_8LEVEL  3
00032 #define ORDER_METHOD_SEARCH  4
00033 #define ORDER_METHOD_LOG     5
00034 
00035 #define MIN_LPC_ORDER        1
00036 #define MAX_LPC_ORDER       32
00037 
00038 
00042 int ff_lpc_calc_coefs(DSPContext *s,
00043                       const int32_t *samples, int blocksize, int min_order,
00044                       int max_order, int precision,
00045                       int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc,
00046                       int omethod, int max_shift, int zero_shift);
00047 
00048 #ifdef LPC_USE_DOUBLE
00049 #define LPC_TYPE double
00050 #else
00051 #define LPC_TYPE float
00052 #endif
00053 
00058 static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
00059                                     LPC_TYPE *lpc, int lpc_stride, int fail,
00060                                     int normalize)
00061 {
00062     int i, j;
00063     LPC_TYPE err;
00064     LPC_TYPE *lpc_last = lpc;
00065 
00066     if (normalize)
00067         err = *autoc++;
00068 
00069     if (fail && (autoc[max_order - 1] == 0 || err <= 0))
00070         return -1;
00071 
00072     for(i=0; i<max_order; i++) {
00073         LPC_TYPE r = -autoc[i];
00074 
00075         if (normalize) {
00076             for(j=0; j<i; j++)
00077                 r -= lpc_last[j] * autoc[i-j-1];
00078 
00079             r /= err;
00080             err *= 1.0 - (r * r);
00081         }
00082 
00083         lpc[i] = r;
00084 
00085         for(j=0; j < (i+1)>>1; j++) {
00086             LPC_TYPE f = lpc_last[    j];
00087             LPC_TYPE b = lpc_last[i-1-j];
00088             lpc[    j] = f + r * b;
00089             lpc[i-1-j] = b + r * f;
00090         }
00091 
00092         if (fail && err < 0)
00093             return -1;
00094 
00095         lpc_last = lpc;
00096         lpc += lpc_stride;
00097     }
00098 
00099     return 0;
00100 }
00101 
00102 #endif /* AVCODEC_LPC_H */

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