libsidplayfp  2.11.0
mixer.h
1 /*
2  * This file is part of libsidplayfp, a SID player engine.
3  *
4  * Copyright 2011-2023 Leandro Nini <drfiemost@users.sourceforge.net>
5  * Copyright 2007-2010 Antti Lankila
6  * Copyright (C) 2000 Simon White
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2 of the License, or
11  * (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16  * GNU General Public License for more details.
17  *
18  * You should have received a copy of the GNU General Public License
19  * along with this program; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 
24 #ifndef MIXER_H
25 #define MIXER_H
26 
27 #include "sidcxx11.h"
28 
29 #include <stdint.h>
30 
31 #include <vector>
32 
33 namespace libsidplayfp
34 {
35 
36 class sidemu;
37 
41 class Mixer
42 {
43 private:
44  // random number generator for dithering
45  template <int MAX_VAL>
46  class randomLCG
47  {
48  static_assert((MAX_VAL != 0) && ((MAX_VAL & (MAX_VAL - 1)) == 0), "MAX_VAL must be a power of two");
49 
50  private:
51  uint32_t rand_seed;
52 
53  public:
54  randomLCG(uint32_t seed) :
55  rand_seed(seed)
56  {}
57 
58  int get()
59  {
60  rand_seed = (214013 * rand_seed + 2531011);
61  return static_cast<int>((rand_seed >> 16) & (MAX_VAL-1));
62  }
63  };
64 
65 public:
66  class badBufferSize {};
67 
68 public:
70  static constexpr unsigned int MAX_SIDS = 3;
71 
72  static constexpr int_least32_t SCALE_FACTOR = 1 << 16;
73 
74  static constexpr double SQRT_0_5 = 0.70710678118654746;
75 
76  static constexpr int_least32_t C1 = static_cast<int_least32_t>(1.0 / (1.0 + SQRT_0_5) * SCALE_FACTOR);
77  static constexpr int_least32_t C2 = static_cast<int_least32_t>(SQRT_0_5 / (1.0 + SQRT_0_5) * SCALE_FACTOR);
78 
79 private:
80  using mixer_func_t = int_least32_t (Mixer::*)() const;
81 
82  using scale_func_t = int (Mixer::*)(unsigned int);
83 
84 public:
86  static constexpr int_least32_t VOLUME_MAX = 1024;
87 
88 private:
89  std::vector<sidemu*> m_chips;
90  std::vector<short*> m_buffers;
91 
92  std::vector<int_least32_t> m_iSamples;
93  std::vector<int_least32_t> m_volume;
94 
95  std::vector<mixer_func_t> m_mix;
96  std::vector<scale_func_t> m_scale;
97 
98  int m_oldRandomValue = 0;
99  int m_fastForwardFactor = 1;
100 
101  // Mixer settings
102  short *m_sampleBuffer = nullptr;
103  uint_least32_t m_sampleCount = 0;
104  uint_least32_t m_sampleIndex = 0;
105 
106  uint_least32_t m_sampleRate = 0;
107 
108  bool m_stereo = false;
109 
110  bool m_wait = false;
111 
112  randomLCG<VOLUME_MAX> m_rand;
113 
114 private:
115  void updateParams();
116 
117  int triangularDithering()
118  {
119  const int prevValue = m_oldRandomValue;
120  m_oldRandomValue = m_rand.get();
121  return m_oldRandomValue - prevValue;
122  }
123 
124  int scale(unsigned int ch)
125  {
126  const int_least32_t sample = (this->*(m_mix[ch]))();
127  return (sample * m_volume[ch] + triangularDithering()) / VOLUME_MAX;
128  }
129 
130  int noScale(unsigned int ch)
131  {
132  return (this->*(m_mix[ch]))();
133  }
134 
135  /*
136  * Channel matrix
137  *
138  * C1
139  * L 1.0
140  * R 1.0
141  *
142  * C1 C2
143  * L 1.0 0.0
144  * R 0.0 1.0
145  *
146  * C1 C2 C3
147  * L 1/1.707 0.707/1.707 0.0
148  * R 0.0 0.707/1.707 1/1.707
149  *
150  * FIXME
151  * it seems that scaling down the summed signals is not the correct way of mixing, see:
152  * http://dsp.stackexchange.com/questions/3581/algorithms-to-mix-audio-signals-without-clipping
153  * maybe we should consider some form of soft/hard clipping instead to avoid possible overflows
154  */
155 
156  // Mono mixing
157  template <int Chips>
158  int_least32_t mono() const
159  {
160  int_least32_t res = 0;
161  for (int i = 0; i < Chips; i++)
162  res += m_iSamples[i];
163  return res / Chips;
164  }
165 
166  // Stereo mixing
167  int_least32_t stereo_OneChip() const { return m_iSamples[0]; }
168 
169  int_least32_t stereo_ch1_TwoChips() const { return m_iSamples[0]; }
170  int_least32_t stereo_ch2_TwoChips() const { return m_iSamples[1]; }
171 
172  int_least32_t stereo_ch1_ThreeChips() const { return (C1*m_iSamples[0] + C2*m_iSamples[1]) / SCALE_FACTOR; }
173  int_least32_t stereo_ch2_ThreeChips() const { return (C2*m_iSamples[1] + C1*m_iSamples[2]) / SCALE_FACTOR; }
174 
175 public:
179  Mixer() :
180  m_rand(257254)
181  {
182  m_mix.push_back(&Mixer::mono<1>);
183  }
184 
188  void doMix();
189 
193  void clockChips();
194 
198  void resetBufs();
199 
208  void begin(short *buffer, uint_least32_t count);
209 
213  void clearSids();
214 
220  void addSid(sidemu *chip);
221 
228  sidemu* getSid(unsigned int i) const { return (i < m_chips.size()) ? m_chips[i] : nullptr; }
229 
236  bool setFastForward(int ff);
237 
244  void setVolume(int_least32_t left, int_least32_t right);
245 
251  void setStereo(bool stereo);
252 
258  void setSamplerate(uint_least32_t rate);
259 
263  bool notFinished() const { return m_sampleIndex < m_sampleCount; }
264 
268  uint_least32_t samplesGenerated() const { return m_sampleIndex; }
269 
270  /*
271  * Wait till we consume the buffer.
272  */
273  bool wait() const { return m_wait; }
274 };
275 
276 }
277 
278 #endif // MIXER_H
Definition: mixer.h:42
void addSid(sidemu *chip)
Definition: mixer.cpp:140
void resetBufs()
Definition: mixer.cpp:40
Mixer()
Definition: mixer.h:179
void clearSids()
Definition: mixer.cpp:134
bool notFinished() const
Definition: mixer.h:263
void clockChips()
Definition: mixer.cpp:34
void setStereo(bool stereo)
Definition: mixer.cpp:154
void setVolume(int_least32_t left, int_least32_t right)
Definition: mixer.cpp:180
static constexpr int_least32_t VOLUME_MAX
Maximum allowed volume, must be a power of 2.
Definition: mixer.h:86
uint_least32_t samplesGenerated() const
Definition: mixer.h:268
void setSamplerate(uint_least32_t rate)
Definition: mixer.cpp:166
void doMix()
Definition: mixer.cpp:46
void begin(short *buffer, uint_least32_t count)
Definition: mixer.cpp:102
static constexpr unsigned int MAX_SIDS
Maximum number of supported SIDs.
Definition: mixer.h:70
bool setFastForward(int ff)
Definition: mixer.cpp:171
sidemu * getSid(unsigned int i) const
Definition: mixer.h:228
Definition: sidemu.h:47