lilium-voyager/code/opus-1.1/silk/fixed/apply_sine_window_FIX.c

/***********************************************************************
Copyright (c) 2006-2011, Skype Limited. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
- Redistributions of source code must retain the above copyright notice,
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
names of specific contributors, may be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
***********************************************************************/

#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 ) );
    }
}