Line data    Source code

       1             : /***********************************************************************
       2             : Copyright (c) 2006-2011, Skype Limited. All rights reserved.
       3             : Redistribution and use in source and binary forms, with or without
       4             : modification, are permitted provided that the following conditions
       5             : are met:
       6             : - Redistributions of source code must retain the above copyright notice,
       7             : this list of conditions and the following disclaimer.
       8             : - Redistributions in binary form must reproduce the above copyright
       9             : notice, this list of conditions and the following disclaimer in the
      10             : documentation and/or other materials provided with the distribution.
      11             : - Neither the name of Internet Society, IETF or IETF Trust, nor the
      12             : names of specific contributors, may be used to endorse or promote
      13             : products derived from this software without specific prior written
      14             : permission.
      15             : THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
      16             : AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
      17             : IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
      18             : ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
      19             : LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
      20             : CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
      21             : SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
      22             : INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
      23             : CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
      24             : ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
      25             : POSSIBILITY OF SUCH DAMAGE.
      26             : ***********************************************************************/
      27             : 
      28             : #ifdef HAVE_CONFIG_H
      29             : #include "config.h"
      30             : #endif
      31             : 
      32             : #include "SigProc_FIX.h"
      33             : #include "resampler_rom.h"
      34             : 
      35             : /* Downsample by a factor 2 */
      36           0 : void silk_resampler_down2(
      37             :     opus_int32                  *S,                 /* I/O  State vector [ 2 ]                                          */
      38             :     opus_int16                  *out,               /* O    Output signal [ floor(len/2) ]                              */
      39             :     const opus_int16            *in,                /* I    Input signal [ len ]                                        */
      40             :     opus_int32                  inLen               /* I    Number of input samples                                     */
      41             : )
      42             : {
      43           0 :     opus_int32 k, len2 = silk_RSHIFT32( inLen, 1 );
      44             :     opus_int32 in32, out32, Y, X;
      45             : 
      46           0 :     silk_assert( silk_resampler_down2_0 > 0 );
      47           0 :     silk_assert( silk_resampler_down2_1 < 0 );
      48             : 
      49             :     /* Internal variables and state are in Q10 format */
      50           0 :     for( k = 0; k < len2; k++ ) {
      51             :         /* Convert to Q10 */
      52           0 :         in32 = silk_LSHIFT( (opus_int32)in[ 2 * k ], 10 );
      53             : 
      54             :         /* All-pass section for even input sample */
      55           0 :         Y      = silk_SUB32( in32, S[ 0 ] );
      56           0 :         X      = silk_SMLAWB( Y, Y, silk_resampler_down2_1 );
      57           0 :         out32  = silk_ADD32( S[ 0 ], X );
      58           0 :         S[ 0 ] = silk_ADD32( in32, X );
      59             : 
      60             :         /* Convert to Q10 */
      61           0 :         in32 = silk_LSHIFT( (opus_int32)in[ 2 * k + 1 ], 10 );
      62             : 
      63             :         /* All-pass section for odd input sample, and add to output of previous section */
      64           0 :         Y      = silk_SUB32( in32, S[ 1 ] );
      65           0 :         X      = silk_SMULWB( Y, silk_resampler_down2_0 );
      66           0 :         out32  = silk_ADD32( out32, S[ 1 ] );
      67           0 :         out32  = silk_ADD32( out32, X );
      68           0 :         S[ 1 ] = silk_ADD32( in32, X );
      69             : 
      70             :         /* Add, convert back to int16 and store to output */
      71           0 :         out[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( out32, 11 ) );
      72             :     }
      73           0 : }
      74             :