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 |
| 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 | |
| 34 | /* Coefficients for 2-band filter bank based on first-order allpass filters */ |
| 35 | static opus_int16 A_fb1_20 = 5394 << 1; |
| 36 | static opus_int16 A_fb1_21 = -24290; /* (opus_int16)(20623 << 1) */ |
| 37 | |
| 38 | /* Split signal into two decimated bands using first-order allpass filters */ |
| 39 | void silk_ana_filt_bank_1( |
| 40 | const opus_int16 *in, /* I Input signal [N] */ |
| 41 | opus_int32 *S, /* I/O State vector [2] */ |
| 42 | opus_int16 *outL, /* O Low band [N/2] */ |
| 43 | opus_int16 *outH, /* O High band [N/2] */ |
| 44 | const opus_int32 N /* I Number of input samples */ |
| 45 | ) |
| 46 | { |
| 47 | opus_int k, N2 = silk_RSHIFT( N, 1 ); |
| 48 | opus_int32 in32, X, Y, out_1, out_2; |
| 49 | |
| 50 | /* Internal variables and state are in Q10 format */ |
| 51 | for( k = 0; k < N2; k++ ) { |
| 52 | /* Convert to Q10 */ |
| 53 | in32 = silk_LSHIFT( (opus_int32)in[ 2 * k ], 10 ); |
| 54 | |
| 55 | /* All-pass section for even input sample */ |
| 56 | Y = silk_SUB32( in32, S[ 0 ] ); |
| 57 | X = silk_SMLAWB( Y, Y, A_fb1_21 ); |
| 58 | out_1 = silk_ADD32( S[ 0 ], X ); |
| 59 | S[ 0 ] = silk_ADD32( in32, X ); |
| 60 | |
| 61 | /* Convert to Q10 */ |
| 62 | in32 = silk_LSHIFT( (opus_int32)in[ 2 * k + 1 ], 10 ); |
| 63 | |
| 64 | /* All-pass section for odd input sample, and add to output of previous section */ |
| 65 | Y = silk_SUB32( in32, S[ 1 ] ); |
| 66 | X = silk_SMULWB( Y, A_fb1_20 ); |
| 67 | out_2 = silk_ADD32( S[ 1 ], X ); |
| 68 | S[ 1 ] = silk_ADD32( in32, X ); |
| 69 | |
| 70 | /* Add/subtract, convert back to int16 and store to output */ |
| 71 | outL[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( silk_ADD32( out_2, out_1 ), 11 ) ); |
| 72 | outH[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( silk_SUB32( out_2, out_1 ), 11 ) ); |
| 73 | } |
| 74 | } |