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| Copyright (c) 2006-2011, Skype Limited. All rights reserved. |
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| modification, are permitted provided that the following conditions |
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| this list of conditions and the following disclaimer. |
| - Redistributions in binary form must reproduce the above copyright |
| notice, this list of conditions and the following disclaimer in the |
| documentation and/or other materials provided with the distribution. |
| - Neither the name of Internet Society, IETF or IETF Trust, nor the |
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| products derived from this software without specific prior written |
| permission. |
| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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| ***********************************************************************/ |
| |
| #ifdef HAVE_CONFIG_H |
| #include "config.h" |
| #endif |
| |
| #include "SigProc_FIX.h" |
| |
| /* Apply sine window to signal vector. */ |
| /* Window types: */ |
| /* 1 -> sine window from 0 to pi/2 */ |
| /* 2 -> sine window from pi/2 to pi */ |
| /* Every other sample is linearly interpolated, for speed. */ |
| /* Window length must be between 16 and 120 (incl) and a multiple of 4. */ |
| |
| /* Matlab code for table: |
| for k=16:9*4:16+2*9*4, fprintf(' %7.d,', -round(65536*pi ./ (k:4:k+8*4))); fprintf('\n'); end |
| */ |
| static const opus_int16 freq_table_Q16[ 27 ] = { |
| 12111, 9804, 8235, 7100, 6239, 5565, 5022, 4575, 4202, |
| 3885, 3612, 3375, 3167, 2984, 2820, 2674, 2542, 2422, |
| 2313, 2214, 2123, 2038, 1961, 1889, 1822, 1760, 1702, |
| }; |
| |
| void silk_apply_sine_window( |
| opus_int16 px_win[], /* O Pointer to windowed signal */ |
| const opus_int16 px[], /* I Pointer to input signal */ |
| const opus_int win_type, /* I Selects a window type */ |
| const opus_int length /* I Window length, multiple of 4 */ |
| ) |
| { |
| opus_int k, f_Q16, c_Q16; |
| opus_int32 S0_Q16, S1_Q16; |
| |
| silk_assert( win_type == 1 || win_type == 2 ); |
| |
| /* Length must be in a range from 16 to 120 and a multiple of 4 */ |
| silk_assert( length >= 16 && length <= 120 ); |
| silk_assert( ( length & 3 ) == 0 ); |
| |
| /* Frequency */ |
| k = ( length >> 2 ) - 4; |
| silk_assert( k >= 0 && k <= 26 ); |
| f_Q16 = (opus_int)freq_table_Q16[ k ]; |
| |
| /* Factor used for cosine approximation */ |
| c_Q16 = silk_SMULWB( (opus_int32)f_Q16, -f_Q16 ); |
| silk_assert( c_Q16 >= -32768 ); |
| |
| /* initialize state */ |
| if( win_type == 1 ) { |
| /* start from 0 */ |
| S0_Q16 = 0; |
| /* approximation of sin(f) */ |
| S1_Q16 = f_Q16 + silk_RSHIFT( length, 3 ); |
| } else { |
| /* start from 1 */ |
| S0_Q16 = ( (opus_int32)1 << 16 ); |
| /* approximation of cos(f) */ |
| S1_Q16 = ( (opus_int32)1 << 16 ) + silk_RSHIFT( c_Q16, 1 ) + silk_RSHIFT( length, 4 ); |
| } |
| |
| /* Uses the recursive equation: sin(n*f) = 2 * cos(f) * sin((n-1)*f) - sin((n-2)*f) */ |
| /* 4 samples at a time */ |
| for( k = 0; k < length; k += 4 ) { |
| px_win[ k ] = (opus_int16)silk_SMULWB( silk_RSHIFT( S0_Q16 + S1_Q16, 1 ), px[ k ] ); |
| px_win[ k + 1 ] = (opus_int16)silk_SMULWB( S1_Q16, px[ k + 1] ); |
| S0_Q16 = silk_SMULWB( S1_Q16, c_Q16 ) + silk_LSHIFT( S1_Q16, 1 ) - S0_Q16 + 1; |
| S0_Q16 = silk_min( S0_Q16, ( (opus_int32)1 << 16 ) ); |
| |
| px_win[ k + 2 ] = (opus_int16)silk_SMULWB( silk_RSHIFT( S0_Q16 + S1_Q16, 1 ), px[ k + 2] ); |
| px_win[ k + 3 ] = (opus_int16)silk_SMULWB( S0_Q16, px[ k + 3 ] ); |
| S1_Q16 = silk_SMULWB( S0_Q16, c_Q16 ) + silk_LSHIFT( S0_Q16, 1 ) - S1_Q16; |
| S1_Q16 = silk_min( S1_Q16, ( (opus_int32)1 << 16 ) ); |
| } |
| } |