1  /*
 2  Copyright (C) 1994-1995 Apogee Software, Ltd.
 3  
 4  This program is free software; you can redistribute it and/or
 5  modify it under the terms of the GNU General Public License
 6  as published by the Free Software Foundation; either version 2
 7  of the License, or (at your option) any later version.
 8  
 9  This program is distributed in the hope that it will be useful,
10  but WITHOUT ANY WARRANTY; without even the implied warranty of
11  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
12  
13  See the GNU General Public License for more details.
14  
15  You should have received a copy of the GNU General Public License
16  along with this program; if not, write to the Free Software
17  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
18  
19  */
20  /**********************************************************************
21     module: PITCH.C
22  
23     author: James R. Dose
24     date:   June 14, 1993
25  
26     Routines for pitch scaling.
27  
28     (c) Copyright 1993 James R. Dose.  All Rights Reserved.
29  **********************************************************************/
30  
31  #include "compat.h"
32  #include "pitch.h"
33  
34  #define MAXDETUNE 50
35  
36  static uint32_t PitchTable[12][MAXDETUNE];
37  
38  
39  /*---------------------------------------------------------------------
40     Function: PITCH_Init
41  
42     Initializes pitch table.
43  ---------------------------------------------------------------------*/
44  
45  
46  void PITCH_Init(void)
47  {
48      for (int note = 0; note < 12; note++)
49          for (int detune = 0; detune < MAXDETUNE; detune++)
50              PitchTable[note][detune] = (uint32_t) (65536.f * powf(2.f, (note * MAXDETUNE + detune) / (12.f * MAXDETUNE)));
51  }
52  
53  
54  /*---------------------------------------------------------------------
55     Function: PITCH_GetScale
56  
57     Returns a fixed-point value to scale number the specified amount.
58  ---------------------------------------------------------------------*/
59  
60  uint32_t PITCH_GetScale(int const pitchoffset)
61  {
62      static bool bInitialized;
63  
64      if (!bInitialized)
65      {
66          PITCH_Init();
67          bInitialized = true;
68      }
69  
70      if (pitchoffset == 0)
71          return PitchTable[0][0];
72  
73      int noteshift = pitchoffset % 1200;
74  
75      if (noteshift < 0)
76          noteshift += 1200;
77  
78      int const   note   = noteshift / 100;
79      int const   detune = (noteshift % 100) / (100 / MAXDETUNE);
80      int const   oshift = (pitchoffset - noteshift) / 1200;
81      auto const &scale  = PitchTable[note][detune];
82  
83      return (oshift < 0) ? (scale >> -oshift) : (scale << oshift);
84  }