dbc223eb84
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108 lines
2.9 KiB
C
108 lines
2.9 KiB
C
/*(LGPL)
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---------------------------------------------------------------------------
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a_pitch.h - 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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#ifndef _PITCHTAB_H_
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#define _PITCHTAB_H_
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#ifdef __cplusplus
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extern "C" {
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#endif
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extern int *__pitchtab;
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/*
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* 'middle_c' is the output value you want with an input of
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* 60; MIDI standard middle C. The table will start 5 octaves
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* down from there, and will contain 129 semitone steps. (The
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* last step is for sub-semitone interpolation.)
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*/
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int ptab_init(int middle_c);
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void ptab_close(void);
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/*
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* Interpolated linear frequency -> frequency factor lookup.
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*
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* 'pith' is a 16:16 fixed point linear frequency value.
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*
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* Returns engine pitch as 16:16 fixed point.
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*/
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static inline int ptab_convert(int pitch)
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{
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int bfrac;
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int btone = pitch >> 16;
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if(btone < 0)
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return __pitchtab[0];
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else if(btone > 127)
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return __pitchtab[128];
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bfrac = (pitch & 0xffff) >> 8;
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return (__pitchtab[btone+1] * bfrac +
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__pitchtab[btone] * (256-bfrac)) >> 8;
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}
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/*
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* Interpolated linear frequency -> frequency factor lookup,
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* MIDI style.
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*
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* 'pith' is a MIDI pitch code (0..127; 60 <==> middle C,
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* which maps to the original sample rate of the current
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* waveform).
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*
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* 'bend' is a 16:16 fixed point value in the same unit.
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* That is, the integer part of bend is added to pitch,
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* whereas the fraction part is used for fractional tone
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* interpolation.
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*
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* Returns engine pitch as 16:16 fixed point.
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*/
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#define ptab_convert_midi(p, b) ptab_convert((b) + ((p)<<16))
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#if 0
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static inline int ptab_convert_midi(int pitch, int bend)
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{
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int bfrac;
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int btone = pitch + (bend >> 16);
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if(btone < 0)
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return __pitchtab[0];
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else if(btone > 127)
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return __pitchtab[128];
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bfrac = (bend & 0xffff) >> 8;
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return (__pitchtab[btone+1] * bfrac +
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__pitchtab[btone] * (256-bfrac)) >> 8;
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}
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#endif
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/*
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* Simple semitone resolution lookup - nonchecking.
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*/
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#define _ptab_lookup(p) (__pitchtab[p])
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/*
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* ...and with checking.
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*/
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#define ptab_lookup(p) (__pitchtab ? _ptab_lookup(p) : 65536)
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#ifdef __cplusplus
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};
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#endif
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#endif /*_PITCHTAB_H_*/
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