Alexandre Lision | 744f742 | 2013-09-25 11:39:37 -0400 | [diff] [blame] | 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 |
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| 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 | /* * |
| 29 | * silk_biquad_alt.c * |
| 30 | * * |
| 31 | * Second order ARMA filter * |
| 32 | * Can handle slowly varying filter coefficients * |
| 33 | * */ |
| 34 | |
| 35 | #ifdef HAVE_CONFIG_H |
| 36 | #include "config.h" |
| 37 | #endif |
| 38 | |
| 39 | #include "SigProc_FIX.h" |
| 40 | |
| 41 | /* Second order ARMA filter, alternative implementation */ |
| 42 | void silk_biquad_alt( |
| 43 | const opus_int16 *in, /* I input signal */ |
| 44 | const opus_int32 *B_Q28, /* I MA coefficients [3] */ |
| 45 | const opus_int32 *A_Q28, /* I AR coefficients [2] */ |
| 46 | opus_int32 *S, /* I/O State vector [2] */ |
| 47 | opus_int16 *out, /* O output signal */ |
| 48 | const opus_int32 len, /* I signal length (must be even) */ |
| 49 | opus_int stride /* I Operate on interleaved signal if > 1 */ |
| 50 | ) |
| 51 | { |
| 52 | /* DIRECT FORM II TRANSPOSED (uses 2 element state vector) */ |
| 53 | opus_int k; |
| 54 | opus_int32 inval, A0_U_Q28, A0_L_Q28, A1_U_Q28, A1_L_Q28, out32_Q14; |
| 55 | |
| 56 | /* Negate A_Q28 values and split in two parts */ |
| 57 | A0_L_Q28 = ( -A_Q28[ 0 ] ) & 0x00003FFF; /* lower part */ |
| 58 | A0_U_Q28 = silk_RSHIFT( -A_Q28[ 0 ], 14 ); /* upper part */ |
| 59 | A1_L_Q28 = ( -A_Q28[ 1 ] ) & 0x00003FFF; /* lower part */ |
| 60 | A1_U_Q28 = silk_RSHIFT( -A_Q28[ 1 ], 14 ); /* upper part */ |
| 61 | |
| 62 | for( k = 0; k < len; k++ ) { |
| 63 | /* S[ 0 ], S[ 1 ]: Q12 */ |
| 64 | inval = in[ k * stride ]; |
| 65 | out32_Q14 = silk_LSHIFT( silk_SMLAWB( S[ 0 ], B_Q28[ 0 ], inval ), 2 ); |
| 66 | |
| 67 | S[ 0 ] = S[1] + silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14, A0_L_Q28 ), 14 ); |
| 68 | S[ 0 ] = silk_SMLAWB( S[ 0 ], out32_Q14, A0_U_Q28 ); |
| 69 | S[ 0 ] = silk_SMLAWB( S[ 0 ], B_Q28[ 1 ], inval); |
| 70 | |
| 71 | S[ 1 ] = silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14, A1_L_Q28 ), 14 ); |
| 72 | S[ 1 ] = silk_SMLAWB( S[ 1 ], out32_Q14, A1_U_Q28 ); |
| 73 | S[ 1 ] = silk_SMLAWB( S[ 1 ], B_Q28[ 2 ], inval ); |
| 74 | |
| 75 | /* Scale back to Q0 and saturate */ |
| 76 | out[ k * stride ] = (opus_int16)silk_SAT16( silk_RSHIFT( out32_Q14 + (1<<14) - 1, 14 ) ); |
| 77 | } |
| 78 | } |