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| permission. |
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| ***********************************************************************/ |
| |
| #ifdef HAVE_CONFIG_H |
| #include "config.h" |
| #endif |
| |
| #include "SigProc_FLP.h" |
| #include "tuning_parameters.h" |
| #include "define.h" |
| |
| /* This code implements the method from https://www.opus-codec.org/docs/vos_fastburg.pdf */ |
| |
| /* Compute reflection coefficients from input signal */ |
| silk_float silk_burg_modified_FLP( |
| silk_float af[], /* O prediction coefficients (length order) */ |
| const silk_float x[], /* I input signal, length: nb_subfr*(D+L_sub) */ |
| const silk_float minInvGain, /* I minimum inverse prediction gain */ |
| const opus_int subfr_length, /* I input signal subframe length (incl. D preceding samples) */ |
| const opus_int nb_subfr, /* I number of subframes stacked in x */ |
| const opus_int D /* I order */ |
| ) |
| { |
| opus_int k, n, s, reached_max_gain; |
| double invGain, num, nrg, rc, tmp1, tmp2, x1, x2, atmp; |
| const silk_float *x_ptr; |
| double c[ SILK_MAX_ORDER_LPC + 1 ]; |
| double g[ SILK_MAX_ORDER_LPC + 1 ]; |
| double a[ SILK_MAX_ORDER_LPC ]; |
| |
| /* Compute autocorrelations, added over subframes */ |
| silk_memset( c, 0, (D + 1) * sizeof( double ) ); |
| for( s = 0; s < nb_subfr; s++ ) { |
| x_ptr = x + s * subfr_length; |
| for( n = 0; n < D + 1; n++ ) { |
| c[ n ] += silk_inner_product_FLP( x_ptr, x_ptr + n, subfr_length - n ); |
| } |
| } |
| for( n = 0; n < D + 1; n++ ) { |
| c[ n ] *= 2.0; |
| } |
| |
| /* Initialize */ |
| c[ 0 ] += FIND_LPC_COND_FAC * c[ 0 ] + 1e-9f ; |
| g[ 0 ] = c[ 0 ]; |
| tmp1 = 0.0f; |
| for( s = 0; s < nb_subfr; s++ ) { |
| x_ptr = x + s * subfr_length; |
| x1 = x_ptr[ 0 ]; |
| x2 = x_ptr[ subfr_length - 1 ]; |
| tmp1 += x1 * x1 + x2 * x2; |
| } |
| g[ 0 ] -= tmp1; |
| g[ 1 ] = c[ 1 ]; |
| rc = - g[ 1 ] / g[ 0 ]; |
| silk_assert( rc > -1.0 && rc < 1.0 ); |
| a[ 0 ] = rc; |
| invGain = ( 1.0 - rc * rc ); |
| reached_max_gain = 0; |
| for( n = 1; n < D; n++ ) { |
| for( k = 0; k < (n >> 1) + 1; k++ ) { |
| tmp1 = g[ k ]; |
| tmp2 = g[ n - k ]; |
| g[ k ] = tmp1 + rc * tmp2; |
| g[ n - k ] = tmp2 + rc * tmp1; |
| } |
| for( s = 0; s < nb_subfr; s++ ) { |
| x_ptr = x + s * subfr_length; |
| x1 = x_ptr[ n ]; |
| x2 = x_ptr[ subfr_length - n - 1 ]; |
| tmp1 = x1; |
| tmp2 = x2; |
| for( k = 0; k < n; k++ ) { |
| atmp = a[ k ]; |
| c[ k + 1 ] -= x1 * x_ptr[ n - k - 1 ] + x2 * x_ptr[ subfr_length - n + k ]; |
| tmp1 += x_ptr[ n - k - 1 ] * atmp; |
| tmp2 += x_ptr[ subfr_length - n + k ] * atmp; |
| } |
| for( k = 0; k <= n; k++ ) { |
| g[ k ] -= tmp1 * x_ptr[ n - k ] + tmp2 * x_ptr[ subfr_length - n + k - 1 ]; |
| } |
| } |
| |
| /* Calculate nominator and denominator for the next order reflection (parcor) coefficient */ |
| tmp1 = c[ n + 1 ]; |
| num = 0.0f; |
| nrg = g[ 0 ]; |
| for( k = 0; k < n; k++ ) { |
| atmp = a[ k ]; |
| tmp1 += c[ n - k ] * atmp; |
| num += g[ n - k ] * atmp; |
| nrg += g[ k + 1 ] * atmp; |
| } |
| g[ n + 1] = tmp1; |
| num += tmp1; |
| silk_assert( nrg > 0.0 ); |
| |
| /* Calculate the next order reflection (parcor) coefficient */ |
| rc = -num / nrg; |
| silk_assert( rc > -1.0 && rc < 1.0 ); |
| |
| /* Update inverse prediction gain */ |
| tmp1 = invGain * ( 1.0 - rc * rc ); |
| if( tmp1 <= minInvGain ) { |
| /* Max prediction gain exceeded; set reflection coefficient such that max prediction gain is exactly hit */ |
| rc = sqrt( 1.0 - minInvGain / invGain ); |
| if( num > 0 ) { |
| /* Ensure adjusted reflection coefficient has the original sign */ |
| rc = -rc; |
| } |
| invGain = minInvGain; |
| reached_max_gain = 1; |
| } else { |
| invGain = tmp1; |
| } |
| |
| /* Update the AR coefficients */ |
| for( k = 0; k < (n + 1) >> 1; k++ ) { |
| tmp1 = a[ k ]; |
| tmp2 = a[ n - k - 1 ]; |
| a[ k ] = tmp1 + rc * tmp2; |
| a[ n - k - 1 ] = tmp2 + rc * tmp1; |
| } |
| a[ n ] = rc; |
| |
| if( reached_max_gain ) { |
| /* Reached max prediction gain; set remaining coefficients to zero and exit loop */ |
| for( k = n + 1; k < D; k++ ) { |
| a[ k ] = 0.0; |
| } |
| break; |
| } |
| } |
| |
| /* Convert to silk_float */ |
| for( k = 0; k < D; k++ ) { |
| af[ k ] = (silk_float)( -a[ k ] ); |
| } |
| |
| nrg = c[ 0 ] * 0.5 * (1.0 - FIND_LPC_COND_FAC); |
| /* Subtract energy of preceding samples from C0 */ |
| for( s = 0; s < nb_subfr; s++ ) { |
| nrg -= silk_energy_FLP( x + s * subfr_length, D ); |
| } |
| /* Approximate residual energy */ |
| nrg *= invGain; |
| |
| /* Return approximate residual energy */ |
| return (silk_float)nrg; |
| } |