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     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 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     if( inLog_Q7 < 0 ) {
     43         return 0;
     44     } else if ( inLog_Q7 >= 3967 ) {
     45 		return silk_int32_MAX;
     46 	}
     47 
     48     out = silk_LSHIFT( 1, silk_RSHIFT( inLog_Q7, 7 ) );
     49     frac_Q7 = inLog_Q7 & 0x7F;
     50     if( inLog_Q7 < 2048 ) {
     51         /* Piece-wise parabolic approximation */
     52         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         out = silk_MLA( out, silk_RSHIFT( out, 7 ), silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) );
     56     }
     57     return out;
     58 }
     59