allpass.hpp

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// Allpass filter declaration
//
// Written by Jezar at Dreampoint, June 2000
// http://www.dreampoint.co.uk
// This code is public domain
 
/*
 * Copyright © 2015-2023 Synthstrom Audible Limited
 *
 * This file is part of The Synthstrom Audible Deluge Firmware.
 *
 * The Synthstrom Audible Deluge Firmware is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program.
 * If not, see <https://www.gnu.org/licenses/>.
*/
 
#ifndef _allpass_
#define _allpass_
#include "r_typedefs.h"
#include "functions.h"
 
class allpass
{
public:
                    allpass();
            void    setbuffer(int32_t *buf, int size);
    inline  int32_t process(int32_t inp);
            void    mute();
            void    setfeedback(float val);
            float   getfeedback();
// private:
    int32_t feedback;
    int32_t *buffer;
    int     bufsize;
    int     bufidx;
};
 
 
// Big to inline - but crucial for speed
inline int32_t allpass::process(int32_t input)
{
    int32_t output;
    int32_t bufout;
    
    bufout = buffer[bufidx];
    
    output = -input + bufout;
    buffer[bufidx] = input + (bufout >> 1); // Shortcut - because feedback was always one half by default anyway
    //buffer[bufidx] = input + (multiply_32x32_rshift32_rounded(bufout, feedback) << 1);
 
    if(++bufidx >= bufsize) bufidx = 0;
 
    return output;
}
 
#endif//_allpass
 
//ends