dbc223eb84
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61 lines
1.6 KiB
C
61 lines
1.6 KiB
C
/*
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---------------------------------------------------------------------------
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a_pitch.c - Simple fixed point linear pitch table.
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---------------------------------------------------------------------------
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* Copyright (C) 2001, 2002, David Olofson
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <stdlib.h>
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#include "a_globals.h"
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#include "a_pitch.h"
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/*
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* Start pitch, based on the assumption that 1.0 (original
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* sample playback speed) gives you a middle C (MIDI #60).
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*/
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#define FIVE_OCTAVES (1 << 5)
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/* 1 + twelfth root of two */
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#define SEMITONE_MULTIPLIER 1.0594630943592953
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int *__pitchtab = NULL;
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int ptab_init(int middle_c)
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{
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int p;
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double pitch;
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free(__pitchtab);
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__pitchtab = malloc(129 * sizeof(int));
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if(!__pitchtab)
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return -1;
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pitch = (double)middle_c / FIVE_OCTAVES;
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for(p = 0; p < 129; ++p)
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{
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__pitchtab[p] = (int)pitch;
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pitch *= SEMITONE_MULTIPLIER;
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}
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return 0;
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}
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void ptab_close(void)
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{
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free(__pitchtab);
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__pitchtab = NULL;
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}
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