cannam@154: /***********************************************************************
cannam@154: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
cannam@154: Redistribution and use in source and binary forms, with or without
cannam@154: modification, are permitted provided that the following conditions
cannam@154: are met:
cannam@154: - Redistributions of source code must retain the above copyright notice,
cannam@154: this list of conditions and the following disclaimer.
cannam@154: - Redistributions in binary form must reproduce the above copyright
cannam@154: notice, this list of conditions and the following disclaimer in the
cannam@154: documentation and/or other materials provided with the distribution.
cannam@154: - Neither the name of Internet Society, IETF or IETF Trust, nor the
cannam@154: names of specific contributors, may be used to endorse or promote
cannam@154: products derived from this software without specific prior written
cannam@154: permission.
cannam@154: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
cannam@154: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
cannam@154: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
cannam@154: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
cannam@154: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
cannam@154: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
cannam@154: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
cannam@154: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
cannam@154: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
cannam@154: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
cannam@154: POSSIBILITY OF SUCH DAMAGE.
cannam@154: ***********************************************************************/
cannam@154: 
cannam@154: #ifdef HAVE_CONFIG_H
cannam@154: #include "config.h"
cannam@154: #endif
cannam@154: 
cannam@154: #include "SigProc_FIX.h"
cannam@154: #include "resampler_private.h"
cannam@154: #include "stack_alloc.h"
cannam@154: 
cannam@154: #define ORDER_FIR                   4
cannam@154: 
cannam@154: /* Downsample by a factor 2/3, low quality */
cannam@154: void silk_resampler_down2_3(
cannam@154:     opus_int32                  *S,                 /* I/O  State vector [ 6 ]                                          */
cannam@154:     opus_int16                  *out,               /* O    Output signal [ floor(2*inLen/3) ]                          */
cannam@154:     const opus_int16            *in,                /* I    Input signal [ inLen ]                                      */
cannam@154:     opus_int32                  inLen               /* I    Number of input samples                                     */
cannam@154: )
cannam@154: {
cannam@154:     opus_int32 nSamplesIn, counter, res_Q6;
cannam@154:     VARDECL( opus_int32, buf );
cannam@154:     opus_int32 *buf_ptr;
cannam@154:     SAVE_STACK;
cannam@154: 
cannam@154:     ALLOC( buf, RESAMPLER_MAX_BATCH_SIZE_IN + ORDER_FIR, opus_int32 );
cannam@154: 
cannam@154:     /* Copy buffered samples to start of buffer */
cannam@154:     silk_memcpy( buf, S, ORDER_FIR * sizeof( opus_int32 ) );
cannam@154: 
cannam@154:     /* Iterate over blocks of frameSizeIn input samples */
cannam@154:     while( 1 ) {
cannam@154:         nSamplesIn = silk_min( inLen, RESAMPLER_MAX_BATCH_SIZE_IN );
cannam@154: 
cannam@154:         /* Second-order AR filter (output in Q8) */
cannam@154:         silk_resampler_private_AR2( &S[ ORDER_FIR ], &buf[ ORDER_FIR ], in,
cannam@154:             silk_Resampler_2_3_COEFS_LQ, nSamplesIn );
cannam@154: 
cannam@154:         /* Interpolate filtered signal */
cannam@154:         buf_ptr = buf;
cannam@154:         counter = nSamplesIn;
cannam@154:         while( counter > 2 ) {
cannam@154:             /* Inner product */
cannam@154:             res_Q6 = silk_SMULWB(         buf_ptr[ 0 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
cannam@154:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
cannam@154:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
cannam@154:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
cannam@154: 
cannam@154:             /* Scale down, saturate and store in output array */
cannam@154:             *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
cannam@154: 
cannam@154:             res_Q6 = silk_SMULWB(         buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
cannam@154:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
cannam@154:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
cannam@154:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 4 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
cannam@154: 
cannam@154:             /* Scale down, saturate and store in output array */
cannam@154:             *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
cannam@154: 
cannam@154:             buf_ptr += 3;
cannam@154:             counter -= 3;
cannam@154:         }
cannam@154: 
cannam@154:         in += nSamplesIn;
cannam@154:         inLen -= nSamplesIn;
cannam@154: 
cannam@154:         if( inLen > 0 ) {
cannam@154:             /* More iterations to do; copy last part of filtered signal to beginning of buffer */
cannam@154:             silk_memcpy( buf, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
cannam@154:         } else {
cannam@154:             break;
cannam@154:         }
cannam@154:     }
cannam@154: 
cannam@154:     /* Copy last part of filtered signal to the state for the next call */
cannam@154:     silk_memcpy( S, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
cannam@154:     RESTORE_STACK;
cannam@154: }