cannam@154: /***********************************************************************
cannam@154: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
cannam@154: Redistribution and use in source and binary forms, with or without
cannam@154: modification, are permitted provided that the following conditions
cannam@154: are met:
cannam@154: - Redistributions of source code must retain the above copyright notice,
cannam@154: this list of conditions and the following disclaimer.
cannam@154: - Redistributions in binary form must reproduce the above copyright
cannam@154: notice, this list of conditions and the following disclaimer in the
cannam@154: documentation and/or other materials provided with the distribution.
cannam@154: - Neither the name of Internet Society, IETF or IETF Trust, nor the
cannam@154: names of specific contributors, may be used to endorse or promote
cannam@154: products derived from this software without specific prior written
cannam@154: permission.
cannam@154: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
cannam@154: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
cannam@154: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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cannam@154: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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cannam@154: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
cannam@154: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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cannam@154: ***********************************************************************/
cannam@154: 
cannam@154: #ifdef HAVE_CONFIG_H
cannam@154: #include "config.h"
cannam@154: #endif
cannam@154: 
cannam@154: #include "SigProc_FIX.h"
cannam@154: /* Approximation of 128 * log2() (very close inverse of silk_log2lin()) */
cannam@154: /* Convert input to a log scale    */
cannam@154: opus_int32 silk_lin2log(
cannam@154:     const opus_int32            inLin               /* I  input in linear scale                                         */
cannam@154: )
cannam@154: {
cannam@154:     opus_int32 lz, frac_Q7;
cannam@154: 
cannam@154:     silk_CLZ_FRAC( inLin, &lz, &frac_Q7 );
cannam@154: 
cannam@154:     /* Piece-wise parabolic approximation */
cannam@154:     return silk_ADD_LSHIFT32( silk_SMLAWB( frac_Q7, silk_MUL( frac_Q7, 128 - frac_Q7 ), 179 ), 31 - lz, 7 );
cannam@154: }
cannam@154: