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27
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31
32 #include "main_FLP.h"
33
34 /* Autocorrelations for a warped frequency axis */
silk_warped_autocorrelation_FLP(silk_float * corr,const silk_float * input,const silk_float warping,const opus_int length,const opus_int order)35 void silk_warped_autocorrelation_FLP(
36 silk_float *corr, /* O Result [order + 1] */
37 const silk_float *input, /* I Input data to correlate */
38 const silk_float warping, /* I Warping coefficient */
39 const opus_int length, /* I Length of input */
40 const opus_int order /* I Correlation order (even) */
41 )
42 {
43 opus_int n, i;
44 double tmp1, tmp2;
45 double state[ MAX_SHAPE_LPC_ORDER + 1 ] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
46 double C[ MAX_SHAPE_LPC_ORDER + 1 ] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
47
48 /* Order must be even */
49 silk_assert( ( order & 1 ) == 0 );
50
51 /* Loop over samples */
52 for( n = 0; n < length; n++ ) {
53 tmp1 = input[ n ];
54 /* Loop over allpass sections */
55 for( i = 0; i < order; i += 2 ) {
56 /* Output of allpass section */
57 tmp2 = state[ i ] + warping * ( state[ i + 1 ] - tmp1 );
58 state[ i ] = tmp1;
59 C[ i ] += state[ 0 ] * tmp1;
60 /* Output of allpass section */
61 tmp1 = state[ i + 1 ] + warping * ( state[ i + 2 ] - tmp2 );
62 state[ i + 1 ] = tmp2;
63 C[ i + 1 ] += state[ 0 ] * tmp2;
64 }
65 state[ order ] = tmp1;
66 C[ order ] += state[ 0 ] * tmp1;
67 }
68
69 /* Copy correlations in silk_float output format */
70 for( i = 0; i < order + 1; i++ ) {
71 corr[ i ] = ( silk_float )C[ i ];
72 }
73 }
74