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51 lines
2.7 KiB
51 lines
2.7 KiB
/*********************************************************************** |
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Copyright (c) 2006-2011, Skype Limited. All rights reserved. |
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Redistribution and use in source and binary forms, with or without |
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modification, are permitted provided that the following conditions |
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are met: |
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- Redistributions of source code must retain the above copyright notice, |
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this list of conditions and the following disclaimer. |
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- Redistributions in binary form must reproduce the above copyright |
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notice, this list of conditions and the following disclaimer in the |
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documentation and/or other materials provided with the distribution. |
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- Neither the name of Internet Society, IETF or IETF Trust, nor the |
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names of specific contributors, may be used to endorse or promote |
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products derived from this software without specific prior written |
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permission. |
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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POSSIBILITY OF SUCH DAMAGE. |
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***********************************************************************/ |
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#ifdef HAVE_CONFIG_H |
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#include "config.h" |
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#endif |
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#include "SigProc_FIX.h" |
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/* Chirp (bandwidth expand) LP AR filter */ |
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void silk_bwexpander( |
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opus_int16 *ar, /* I/O AR filter to be expanded (without leading 1) */ |
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const opus_int d, /* I Length of ar */ |
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opus_int32 chirp_Q16 /* I Chirp factor (typically in the range 0 to 1) */ |
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) |
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{ |
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opus_int i; |
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opus_int32 chirp_minus_one_Q16 = chirp_Q16 - 65536; |
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/* NB: Dont use silk_SMULWB, instead of silk_RSHIFT_ROUND( silk_MUL(), 16 ), below. */ |
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/* Bias in silk_SMULWB can lead to unstable filters */ |
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for( i = 0; i < d - 1; i++ ) { |
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ar[ i ] = (opus_int16)silk_RSHIFT_ROUND( silk_MUL( chirp_Q16, ar[ i ] ), 16 ); |
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chirp_Q16 += silk_RSHIFT_ROUND( silk_MUL( chirp_Q16, chirp_minus_one_Q16 ), 16 ); |
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} |
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ar[ d - 1 ] = (opus_int16)silk_RSHIFT_ROUND( silk_MUL( chirp_Q16, ar[ d - 1 ] ), 16 ); |
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}
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