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comparison: media/libopus/silk/resampler_down2.c
media/libopus/silk/resampler_down2.c
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| 1 /*********************************************************************** | |
| 2 Copyright (c) 2006-2011, Skype Limited. All rights reserved. | |
| 3 Redistribution and use in source and binary forms, with or without | |
| 4 modification, are permitted provided that the following conditions | |
| 5 are met: | |
| 6 - Redistributions of source code must retain the above copyright notice, | |
| 7 this list of conditions and the following disclaimer. | |
| 8 - Redistributions in binary form must reproduce the above copyright | |
| 9 notice, this list of conditions and the following disclaimer in the | |
| 10 documentation and/or other materials provided with the distribution. | |
| 11 - Neither the name of Internet Society, IETF or IETF Trust, nor the | |
| 12 names of specific contributors, may be used to endorse or promote | |
| 13 products derived from this software without specific prior written | |
| 14 permission. | |
| 15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | |
| 16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE | |
| 19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
| 20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF | |
| 21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS | |
| 22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN | |
| 23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
| 24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
| 25 POSSIBILITY OF SUCH DAMAGE. | |
| 26 ***********************************************************************/ | |
| 27 | |
| 28 #ifdef HAVE_CONFIG_H | |
| 29 #include "config.h" | |
| 30 #endif | |
| 31 | |
| 32 #include "SigProc_FIX.h" | |
| 33 #include "resampler_rom.h" | |
| 34 | |
| 35 /* Downsample by a factor 2 */ | |
| 36 void silk_resampler_down2( | |
| 37 opus_int32 *S, /* I/O State vector [ 2 ] */ | |
| 38 opus_int16 *out, /* O Output signal [ floor(len/2) ] */ | |
| 39 const opus_int16 *in, /* I Input signal [ len ] */ | |
| 40 opus_int32 inLen /* I Number of input samples */ | |
| 41 ) | |
| 42 { | |
| 43 opus_int32 k, len2 = silk_RSHIFT32( inLen, 1 ); | |
| 44 opus_int32 in32, out32, Y, X; | |
| 45 | |
| 46 silk_assert( silk_resampler_down2_0 > 0 ); | |
| 47 silk_assert( silk_resampler_down2_1 < 0 ); | |
| 48 | |
| 49 /* Internal variables and state are in Q10 format */ | |
| 50 for( k = 0; k < len2; k++ ) { | |
| 51 /* Convert to Q10 */ | |
| 52 in32 = silk_LSHIFT( (opus_int32)in[ 2 * k ], 10 ); | |
| 53 | |
| 54 /* All-pass section for even input sample */ | |
| 55 Y = silk_SUB32( in32, S[ 0 ] ); | |
| 56 X = silk_SMLAWB( Y, Y, silk_resampler_down2_1 ); | |
| 57 out32 = silk_ADD32( S[ 0 ], X ); | |
| 58 S[ 0 ] = silk_ADD32( in32, X ); | |
| 59 | |
| 60 /* Convert to Q10 */ | |
| 61 in32 = silk_LSHIFT( (opus_int32)in[ 2 * k + 1 ], 10 ); | |
| 62 | |
| 63 /* All-pass section for odd input sample, and add to output of previous section */ | |
| 64 Y = silk_SUB32( in32, S[ 1 ] ); | |
| 65 X = silk_SMULWB( Y, silk_resampler_down2_0 ); | |
| 66 out32 = silk_ADD32( out32, S[ 1 ] ); | |
| 67 out32 = silk_ADD32( out32, X ); | |
| 68 S[ 1 ] = silk_ADD32( in32, X ); | |
| 69 | |
| 70 /* Add, convert back to int16 and store to output */ | |
| 71 out[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( out32, 11 ) ); | |
| 72 } | |
| 73 } | |
| 74 |
