usr/src/cmd/audio/include/Resample.h

   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 */