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 /* 31 * To convert the sampling rate of fi of input signal to fo of output signal, 32 * the least common multiple fm = L * fi = M * fo needs to be derived first. 33 * Then the input signal is 34 * 1) up-sampled to fm by inserting (L - 1) zero-valued samples after each 35 * input sample, 36 * 2) low-pass filtered to half of the lower of fi and fo, and 37 * 3) down-sampled to fo by saving one out of every M samples. 38 * 39 * The low-pass filter is implemented with an FIR filter which is a truncated 40 * ideal low pass filter whose order is dependent on its bandwidth. 41 * 42 * Refer to Fir.h for explanations of filter() and flush(). 43 * 44 */ 45 #include <Fir.h> 46 47 #ifdef __cplusplus 48 extern "C" { 49 #endif 50 51 class ResampleFilter : public Fir { 52 int num_state; // interpolation requires less states 53 int up; // upsampling ratio 54 int down; // down sampling ratio 55 int down_offset; // 0 <= index in down-sampling < down 56 int up_offset; // -up < index in up_sampling <= 0 57 58 void updateState(double *in, int size); 59 60 // if fi is a multiple of fo, LP filtering followed by down_sampling 61 int decimate_noadjust(short *in, int size, short *out); 62 int decimate_flush(short *); 63 int decimate(short *in, int size, short *out); 64 65 // if fo is a multiple of fi, up-sampling followed by LP filtering 66 int interpolate_noadjust(short *in, int size, short *out); 67 int interpolate_flush(short *); 68 int interpolate(short *in, int size, short *out); 69 70 int flush(short *out); 71 72 public: 73 ResampleFilter(int rate_in, int rate_out); 74 virtual int filter_noadjust(short *in, int size, short *out); 75 virtual int filter(short *in, int size, short *out); 76 virtual int getFlushSize(void); 77 }; 78 79 #ifdef __cplusplus 80 } 81 #endif 82 83 #endif /* !_MULTIMEDIA_RESAMPLE_H */ 84