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: #include "resampler_private.h"
michael@0: #include "stack_alloc.h"
michael@0: 
michael@0: #define ORDER_FIR                   4
michael@0: 
michael@0: /* Downsample by a factor 2/3, low quality */
michael@0: void silk_resampler_down2_3(
michael@0:     opus_int32                  *S,                 /* I/O  State vector [ 6 ]                                          */
michael@0:     opus_int16                  *out,               /* O    Output signal [ floor(2*inLen/3) ]                          */
michael@0:     const opus_int16            *in,                /* I    Input signal [ inLen ]                                      */
michael@0:     opus_int32                  inLen               /* I    Number of input samples                                     */
michael@0: )
michael@0: {
michael@0:     opus_int32 nSamplesIn, counter, res_Q6;
michael@0:     VARDECL( opus_int32, buf );
michael@0:     opus_int32 *buf_ptr;
michael@0:     SAVE_STACK;
michael@0: 
michael@0:     ALLOC( buf, RESAMPLER_MAX_BATCH_SIZE_IN + ORDER_FIR, opus_int32 );
michael@0: 
michael@0:     /* Copy buffered samples to start of buffer */
michael@0:     silk_memcpy( buf, S, ORDER_FIR * sizeof( opus_int32 ) );
michael@0: 
michael@0:     /* Iterate over blocks of frameSizeIn input samples */
michael@0:     while( 1 ) {
michael@0:         nSamplesIn = silk_min( inLen, RESAMPLER_MAX_BATCH_SIZE_IN );
michael@0: 
michael@0:         /* Second-order AR filter (output in Q8) */
michael@0:         silk_resampler_private_AR2( &S[ ORDER_FIR ], &buf[ ORDER_FIR ], in,
michael@0:             silk_Resampler_2_3_COEFS_LQ, nSamplesIn );
michael@0: 
michael@0:         /* Interpolate filtered signal */
michael@0:         buf_ptr = buf;
michael@0:         counter = nSamplesIn;
michael@0:         while( counter > 2 ) {
michael@0:             /* Inner product */
michael@0:             res_Q6 = silk_SMULWB(         buf_ptr[ 0 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
michael@0:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
michael@0:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
michael@0:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
michael@0: 
michael@0:             /* Scale down, saturate and store in output array */
michael@0:             *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
michael@0: 
michael@0:             res_Q6 = silk_SMULWB(         buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
michael@0:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
michael@0:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
michael@0:             res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 4 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
michael@0: 
michael@0:             /* Scale down, saturate and store in output array */
michael@0:             *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
michael@0: 
michael@0:             buf_ptr += 3;
michael@0:             counter -= 3;
michael@0:         }
michael@0: 
michael@0:         in += nSamplesIn;
michael@0:         inLen -= nSamplesIn;
michael@0: 
michael@0:         if( inLen > 0 ) {
michael@0:             /* More iterations to do; copy last part of filtered signal to beginning of buffer */
michael@0:             silk_memcpy( buf, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
michael@0:         } else {
michael@0:             break;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     /* Copy last part of filtered signal to the state for the next call */
michael@0:     silk_memcpy( S, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
michael@0:     RESTORE_STACK;
michael@0: }