1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/media/libopus/silk/log2lin.c Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,58 @@
1.4 +/***********************************************************************
1.5 +Copyright (c) 2006-2011, Skype Limited. All rights reserved.
1.6 +Redistribution and use in source and binary forms, with or without
1.7 +modification, are permitted provided that the following conditions
1.8 +are met:
1.9 +- Redistributions of source code must retain the above copyright notice,
1.10 +this list of conditions and the following disclaimer.
1.11 +- Redistributions in binary form must reproduce the above copyright
1.12 +notice, this list of conditions and the following disclaimer in the
1.13 +documentation and/or other materials provided with the distribution.
1.14 +- Neither the name of Internet Society, IETF or IETF Trust, nor the
1.15 +names of specific contributors, may be used to endorse or promote
1.16 +products derived from this software without specific prior written
1.17 +permission.
1.18 +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
1.19 +AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
1.20 +IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
1.21 +ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
1.22 +LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
1.23 +CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
1.24 +SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
1.25 +INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
1.26 +CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
1.27 +ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
1.28 +POSSIBILITY OF SUCH DAMAGE.
1.29 +***********************************************************************/
1.30 +
1.31 +#ifdef HAVE_CONFIG_H
1.32 +#include "config.h"
1.33 +#endif
1.34 +
1.35 +#include "SigProc_FIX.h"
1.36 +
1.37 +/* Approximation of 2^() (very close inverse of silk_lin2log()) */
1.38 +/* Convert input to a linear scale */
1.39 +opus_int32 silk_log2lin(
1.40 + const opus_int32 inLog_Q7 /* I input on log scale */
1.41 +)
1.42 +{
1.43 + opus_int32 out, frac_Q7;
1.44 +
1.45 + if( inLog_Q7 < 0 ) {
1.46 + return 0;
1.47 + } else if ( inLog_Q7 >= 3967 ) {
1.48 + return silk_int32_MAX;
1.49 + }
1.50 +
1.51 + out = silk_LSHIFT( 1, silk_RSHIFT( inLog_Q7, 7 ) );
1.52 + frac_Q7 = inLog_Q7 & 0x7F;
1.53 + if( inLog_Q7 < 2048 ) {
1.54 + /* Piece-wise parabolic approximation */
1.55 + out = silk_ADD_RSHIFT32( out, silk_MUL( out, silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ), 7 );
1.56 + } else {
1.57 + /* Piece-wise parabolic approximation */
1.58 + out = silk_MLA( out, silk_RSHIFT( out, 7 ), silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) );
1.59 + }
1.60 + return out;
1.61 +}
