/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1992-2001 by Sun Microsystems, Inc.
 * All rights reserved.
 */

#ifndef _MULTIMEDIA_RESAMPLE_H
#define _MULTIMEDIA_RESAMPLE_H

/*
 * To convert the sampling rate of fi of input signal to fo of output signal,
 * the least common multiple fm = L * fi = M * fo needs to be derived first.
 * Then the input signal is
 * 1) up-sampled to fm by inserting (L - 1) zero-valued samples after each
 *    input sample,
 * 2) low-pass filtered to half of the lower of fi and fo, and
 * 3) down-sampled to fo by saving one out of every M samples.
 *
 * The low-pass filter is implemented with an FIR filter which is a truncated
 * ideal low pass filter whose order is dependent on its bandwidth.
 *
 * Refer to Fir.h for explanations of filter() and flush().
 *
 */
#include <Fir.h>

#ifdef __cplusplus
extern "C" {
#endif

class ResampleFilter : public Fir {
        int     num_state;              // interpolation requires less states
        int     up;                     // upsampling ratio
        int     down;                   // down sampling ratio
        int     down_offset;            // 0 <= index in down-sampling < down
        int     up_offset;              // -up < index in up_sampling <= 0

        void updateState(double *in, int size);

        // if fi is a multiple of fo, LP filtering followed by down_sampling
        int decimate_noadjust(short *in, int size, short *out);
        int decimate_flush(short *);
        int decimate(short *in, int size, short *out);

        // if fo is a multiple of fi, up-sampling followed by LP filtering
        int interpolate_noadjust(short *in, int size, short *out);
        int interpolate_flush(short *);
        int interpolate(short *in, int size, short *out);

        int flush(short *out);

public:
        ResampleFilter(int rate_in, int rate_out);
        virtual int     filter_noadjust(short *in, int size, short *out);
        virtual int     filter(short *in, int size, short *out);
        virtual int     getFlushSize(void);
};

#ifdef __cplusplus
}
#endif

#endif /* !_MULTIMEDIA_RESAMPLE_H */