1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright (c) 1992-2001 by Sun Microsystems, Inc. 24 * All rights reserved. 25 */ 26 27 #ifndef _MULTIMEDIA_RESAMPLE_H 28 #define _MULTIMEDIA_RESAMPLE_H 29 30 #pragma ident "%Z%%M% %I% %E% SMI" 31 32 /* 33 * To convert the sampling rate of fi of input signal to fo of output signal, 34 * the least common multiple fm = L * fi = M * fo needs to be derived first. 35 * Then the input signal is 36 * 1) up-sampled to fm by inserting (L - 1) zero-valued samples after each 37 * input sample, 38 * 2) low-pass filtered to half of the lower of fi and fo, and 39 * 3) down-sampled to fo by saving one out of every M samples. 40 * 41 * The low-pass filter is implemented with an FIR filter which is a truncated 42 * ideal low pass filter whose order is dependent on its bandwidth. 43 * 44 * Refer to Fir.h for explanations of filter() and flush(). 45 * 46 */ 47 #include <Fir.h> 48 49 #ifdef __cplusplus 50 extern "C" { 51 #endif 52 53 class ResampleFilter : public Fir { 54 int num_state; // interpolation requires less states 55 int up; // upsampling ratio 56 int down; // down sampling ratio 57 int down_offset; // 0 <= index in down-sampling < down 58 int up_offset; // -up < index in up_sampling <= 0 59 60 void updateState(double *in, int size); 61 62 // if fi is a multiple of fo, LP filtering followed by down_sampling 63 int decimate_noadjust(short *in, int size, short *out); 64 int decimate_flush(short *); 65 int decimate(short *in, int size, short *out); 66 67 // if fo is a multiple of fi, up-sampling followed by LP filtering 68 int interpolate_noadjust(short *in, int size, short *out); 69 int interpolate_flush(short *); 70 int interpolate(short *in, int size, short *out); 71 72 int flush(short *out); 73 74 public: 75 ResampleFilter(int rate_in, int rate_out); 76 virtual int filter_noadjust(short *in, int size, short *out); 77 virtual int filter(short *in, int size, short *out); 78 virtual int getFlushSize(void); 79 }; 80 81 #ifdef __cplusplus 82 } 83 #endif 84 85 #endif /* !_MULTIMEDIA_RESAMPLE_H */ 86