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Diffstat (limited to 'media/libopus/silk/float/levinsondurbin_FLP.c')
| -rw-r--r-- | media/libopus/silk/float/levinsondurbin_FLP.c | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/media/libopus/silk/float/levinsondurbin_FLP.c b/media/libopus/silk/float/levinsondurbin_FLP.c new file mode 100644 index 000000000..f0ba60698 --- /dev/null +++ b/media/libopus/silk/float/levinsondurbin_FLP.c @@ -0,0 +1,81 @@ +/*********************************************************************** +Copyright (c) 2006-2011, Skype Limited. All rights reserved. +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions +are met: +- Redistributions of source code must retain the above copyright notice, +this list of conditions and the following disclaimer. +- Redistributions in binary form must reproduce the above copyright +notice, this list of conditions and the following disclaimer in the +documentation and/or other materials provided with the distribution. +- Neither the name of Internet Society, IETF or IETF Trust, nor the +names of specific contributors, may be used to endorse or promote +products derived from this software without specific prior written +permission. +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" +AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE +LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +POSSIBILITY OF SUCH DAMAGE. +***********************************************************************/ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include "SigProc_FLP.h" + +/* Solve the normal equations using the Levinson-Durbin recursion */ +silk_float silk_levinsondurbin_FLP( /* O prediction error energy */ + silk_float A[], /* O prediction coefficients [order] */ + const silk_float corr[], /* I input auto-correlations [order + 1] */ + const opus_int order /* I prediction order */ +) +{ + opus_int i, mHalf, m; + silk_float min_nrg, nrg, t, km, Atmp1, Atmp2; + + min_nrg = 1e-12f * corr[ 0 ] + 1e-9f; + nrg = corr[ 0 ]; + nrg = silk_max_float(min_nrg, nrg); + A[ 0 ] = corr[ 1 ] / nrg; + nrg -= A[ 0 ] * corr[ 1 ]; + nrg = silk_max_float(min_nrg, nrg); + + for( m = 1; m < order; m++ ) + { + t = corr[ m + 1 ]; + for( i = 0; i < m; i++ ) { + t -= A[ i ] * corr[ m - i ]; + } + + /* reflection coefficient */ + km = t / nrg; + + /* residual energy */ + nrg -= km * t; + nrg = silk_max_float(min_nrg, nrg); + + mHalf = m >> 1; + for( i = 0; i < mHalf; i++ ) { + Atmp1 = A[ i ]; + Atmp2 = A[ m - i - 1 ]; + A[ m - i - 1 ] -= km * Atmp1; + A[ i ] -= km * Atmp2; + } + if( m & 1 ) { + A[ mHalf ] -= km * A[ mHalf ]; + } + A[ m ] = km; + } + + /* return the residual energy */ + return nrg; +} + |