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,
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       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.
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      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
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      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             : 
      34             : /* Approximation of 2^() (very close inverse of silk_lin2log()) */
      35             : /* Convert input to a linear scale    */
      36           0 : opus_int32 silk_log2lin(
      37             :     const opus_int32            inLog_Q7            /* I  input on log scale                                            */
      38             : )
      39             : {
      40             :     opus_int32 out, frac_Q7;
      41             : 
      42           0 :     if( inLog_Q7 < 0 ) {
      43           0 :         return 0;
      44           0 :     } else if ( inLog_Q7 >= 3967 ) {
      45           0 :         return silk_int32_MAX;
      46             :     }
      47             : 
      48           0 :     out = silk_LSHIFT( 1, silk_RSHIFT( inLog_Q7, 7 ) );
      49           0 :     frac_Q7 = inLog_Q7 & 0x7F;
      50           0 :     if( inLog_Q7 < 2048 ) {
      51             :         /* Piece-wise parabolic approximation */
      52           0 :         out = silk_ADD_RSHIFT32( out, silk_MUL( out, silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ), 7 );
      53             :     } else {
      54             :         /* Piece-wise parabolic approximation */
      55           0 :         out = silk_MLA( out, silk_RSHIFT( out, 7 ), silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) );
      56             :     }
      57           0 :     return out;
      58             : }