1*a58d3d2aSXin Li /***********************************************************************
2*a58d3d2aSXin Li Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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7*a58d3d2aSXin Li this list of conditions and the following disclaimer.
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9*a58d3d2aSXin Li notice, this list of conditions and the following disclaimer in the
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26*a58d3d2aSXin Li ***********************************************************************/
27*a58d3d2aSXin Li
28*a58d3d2aSXin Li #ifdef HAVE_CONFIG_H
29*a58d3d2aSXin Li #include "config.h"
30*a58d3d2aSXin Li #endif
31*a58d3d2aSXin Li
32*a58d3d2aSXin Li #include "SigProc_FIX.h"
33*a58d3d2aSXin Li /* Approximation of 128 * log2() (very close inverse of silk_log2lin()) */
34*a58d3d2aSXin Li /* Convert input to a log scale */
silk_lin2log(const opus_int32 inLin)35*a58d3d2aSXin Li opus_int32 silk_lin2log(
36*a58d3d2aSXin Li const opus_int32 inLin /* I input in linear scale */
37*a58d3d2aSXin Li )
38*a58d3d2aSXin Li {
39*a58d3d2aSXin Li opus_int32 lz, frac_Q7;
40*a58d3d2aSXin Li
41*a58d3d2aSXin Li silk_CLZ_FRAC( inLin, &lz, &frac_Q7 );
42*a58d3d2aSXin Li
43*a58d3d2aSXin Li /* Piece-wise parabolic approximation */
44*a58d3d2aSXin Li return silk_ADD_LSHIFT32( silk_SMLAWB( frac_Q7, silk_MUL( frac_Q7, 128 - frac_Q7 ), 179 ), 31 - lz, 7 );
45*a58d3d2aSXin Li }
46*a58d3d2aSXin Li
47