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112 lines
2.9 KiB
C
112 lines
2.9 KiB
C
/*
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Copyright (C) 1994-1995 Apogee Software, Ltd.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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/**********************************************************************
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module: PITCH.C
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author: James R. Dose
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date: June 14, 1993
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Routines for pitch scaling.
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(c) Copyright 1993 James R. Dose. All Rights Reserved.
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**********************************************************************/
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#include <stdlib.h>
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#include <math.h>
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#include "pitch.h"
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#define MAXDETUNE 50
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static uint32_t PitchTable[ 12 ][ MAXDETUNE ];
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static int32_t PITCH_Installed = 0;
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/*---------------------------------------------------------------------
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Function: PITCH_Init
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Initializes pitch table.
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---------------------------------------------------------------------*/
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void PITCH_Init(void)
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{
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int32_t note;
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int32_t detune;
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if (!PITCH_Installed)
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{
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for (note = 0; note < 12; note++)
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{
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for (detune = 0; detune < MAXDETUNE; detune++)
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{
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PitchTable[ note ][ detune ] = 0x10000 *
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pow(2, (note * MAXDETUNE + detune) / (12.0 * MAXDETUNE));
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}
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}
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PITCH_Installed = 1;
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}
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}
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/*---------------------------------------------------------------------
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Function: PITCH_GetScale
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Returns a fixed-point value to scale number the specified amount.
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---------------------------------------------------------------------*/
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uint32_t PITCH_GetScale(int32_t pitchoffset)
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{
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uint32_t scale;
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int32_t octaveshift;
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int32_t noteshift;
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int32_t note;
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int32_t detune;
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if ( !PITCH_Installed )
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PITCH_Init();
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if (pitchoffset == 0)
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return PitchTable[ 0 ][ 0 ];
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noteshift = pitchoffset % 1200;
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if (noteshift < 0)
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noteshift += 1200;
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note = noteshift / 100;
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detune = (noteshift % 100) / (100 / MAXDETUNE);
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octaveshift = (pitchoffset - noteshift) / 1200;
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if (detune < 0)
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{
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detune += (100 / MAXDETUNE);
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note--;
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if (note < 0)
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{
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note += 12;
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octaveshift--;
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}
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}
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scale = PitchTable[ note ][ detune ];
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return (octaveshift < 0) ? (scale >> -octaveshift) : (scale <<= octaveshift);
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}
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