Line data Source code
1 : /***********************************************************************
2 : Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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26 : ***********************************************************************/
27 :
28 : #ifdef HAVE_CONFIG_H
29 : #include "config.h"
30 : #endif
31 :
32 : #include "SigProc_FIX.h"
33 : /* Approximation of 128 * log2() (very close inverse of silk_log2lin()) */
34 : /* Convert input to a log scale */
35 0 : opus_int32 silk_lin2log(
36 : const opus_int32 inLin /* I input in linear scale */
37 : )
38 : {
39 : opus_int32 lz, frac_Q7;
40 :
41 0 : silk_CLZ_FRAC( inLin, &lz, &frac_Q7 );
42 :
43 : /* Piece-wise parabolic approximation */
44 0 : return silk_ADD_LSHIFT32( silk_SMLAWB( frac_Q7, silk_MUL( frac_Q7, 128 - frac_Q7 ), 179 ), 31 - lz, 7 );
45 : }
46 :
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