michael@0: /***********************************************************************
michael@0: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
michael@0: Redistribution and use in source and binary forms, with or without
michael@0: modification, are permitted provided that the following conditions
michael@0: are met:
michael@0: - Redistributions of source code must retain the above copyright notice,
michael@0: this list of conditions and the following disclaimer.
michael@0: - Redistributions in binary form must reproduce the above copyright
michael@0: notice, this list of conditions and the following disclaimer in the
michael@0: documentation and/or other materials provided with the distribution.
michael@0: - Neither the name of Internet Society, IETF or IETF Trust, nor the
michael@0: names of specific contributors, may be used to endorse or promote
michael@0: products derived from this software without specific prior written
michael@0: permission.
michael@0: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
michael@0: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
michael@0: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
michael@0: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
michael@0: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
michael@0: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
michael@0: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
michael@0: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
michael@0: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
michael@0: POSSIBILITY OF SUCH DAMAGE.
michael@0: ***********************************************************************/
michael@0: 
michael@0: #ifdef HAVE_CONFIG_H
michael@0: #include "config.h"
michael@0: #endif
michael@0: 
michael@0: #include "SigProc_FIX.h"
michael@0: 
michael@0: /* Apply sine window to signal vector.                                      */
michael@0: /* Window types:                                                            */
michael@0: /*    1 -> sine window from 0 to pi/2                                       */
michael@0: /*    2 -> sine window from pi/2 to pi                                      */
michael@0: /* Every other sample is linearly interpolated, for speed.                  */
michael@0: /* Window length must be between 16 and 120 (incl) and a multiple of 4.     */
michael@0: 
michael@0: /* Matlab code for table:
michael@0:    for k=16:9*4:16+2*9*4, fprintf(' %7.d,', -round(65536*pi ./ (k:4:k+8*4))); fprintf('\n'); end
michael@0: */
michael@0: static const opus_int16 freq_table_Q16[ 27 ] = {
michael@0:    12111,    9804,    8235,    7100,    6239,    5565,    5022,    4575,    4202,
michael@0:     3885,    3612,    3375,    3167,    2984,    2820,    2674,    2542,    2422,
michael@0:     2313,    2214,    2123,    2038,    1961,    1889,    1822,    1760,    1702,
michael@0: };
michael@0: 
michael@0: void silk_apply_sine_window(
michael@0:     opus_int16                  px_win[],           /* O    Pointer to windowed signal                                  */
michael@0:     const opus_int16            px[],               /* I    Pointer to input signal                                     */
michael@0:     const opus_int              win_type,           /* I    Selects a window type                                       */
michael@0:     const opus_int              length              /* I    Window length, multiple of 4                                */
michael@0: )
michael@0: {
michael@0:     opus_int   k, f_Q16, c_Q16;
michael@0:     opus_int32 S0_Q16, S1_Q16;
michael@0: 
michael@0:     silk_assert( win_type == 1 || win_type == 2 );
michael@0: 
michael@0:     /* Length must be in a range from 16 to 120 and a multiple of 4 */
michael@0:     silk_assert( length >= 16 && length <= 120 );
michael@0:     silk_assert( ( length & 3 ) == 0 );
michael@0: 
michael@0:     /* Frequency */
michael@0:     k = ( length >> 2 ) - 4;
michael@0:     silk_assert( k >= 0 && k <= 26 );
michael@0:     f_Q16 = (opus_int)freq_table_Q16[ k ];
michael@0: 
michael@0:     /* Factor used for cosine approximation */
michael@0:     c_Q16 = silk_SMULWB( (opus_int32)f_Q16, -f_Q16 );
michael@0:     silk_assert( c_Q16 >= -32768 );
michael@0: 
michael@0:     /* initialize state */
michael@0:     if( win_type == 1 ) {
michael@0:         /* start from 0 */
michael@0:         S0_Q16 = 0;
michael@0:         /* approximation of sin(f) */
michael@0:         S1_Q16 = f_Q16 + silk_RSHIFT( length, 3 );
michael@0:     } else {
michael@0:         /* start from 1 */
michael@0:         S0_Q16 = ( (opus_int32)1 << 16 );
michael@0:         /* approximation of cos(f) */
michael@0:         S1_Q16 = ( (opus_int32)1 << 16 ) + silk_RSHIFT( c_Q16, 1 ) + silk_RSHIFT( length, 4 );
michael@0:     }
michael@0: 
michael@0:     /* Uses the recursive equation:   sin(n*f) = 2 * cos(f) * sin((n-1)*f) - sin((n-2)*f)    */
michael@0:     /* 4 samples at a time */
michael@0:     for( k = 0; k < length; k += 4 ) {
michael@0:         px_win[ k ]     = (opus_int16)silk_SMULWB( silk_RSHIFT( S0_Q16 + S1_Q16, 1 ), px[ k ] );
michael@0:         px_win[ k + 1 ] = (opus_int16)silk_SMULWB( S1_Q16, px[ k + 1] );
michael@0:         S0_Q16 = silk_SMULWB( S1_Q16, c_Q16 ) + silk_LSHIFT( S1_Q16, 1 ) - S0_Q16 + 1;
michael@0:         S0_Q16 = silk_min( S0_Q16, ( (opus_int32)1 << 16 ) );
michael@0: 
michael@0:         px_win[ k + 2 ] = (opus_int16)silk_SMULWB( silk_RSHIFT( S0_Q16 + S1_Q16, 1 ), px[ k + 2] );
michael@0:         px_win[ k + 3 ] = (opus_int16)silk_SMULWB( S0_Q16, px[ k + 3 ] );
michael@0:         S1_Q16 = silk_SMULWB( S0_Q16, c_Q16 ) + silk_LSHIFT( S0_Q16, 1 ) - S1_Q16;
michael@0:         S1_Q16 = silk_min( S1_Q16, ( (opus_int32)1 << 16 ) );
michael@0:     }
michael@0: }