204 lines
5.4 KiB
C++
Executable file
204 lines
5.4 KiB
C++
Executable file
// Part of SAASound copyright 1998-2018 Dave Hooper <dave@beermex.com>
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//
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// SAAAmp.cpp: implementation of the CSAAAmp class.
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// This class handles Tone/Noise mixing, Envelope application and
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// amplification.
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//
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//////////////////////////////////////////////////////////////////////
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#include "SAASound.h"
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#include "types.h"
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#include "SAANoise.h"
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#include "SAAEnv.h"
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#include "SAAFreq.h"
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#include "SAAAmp.h"
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#include "defns.h"
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//////////////////////////////////////////////////////////////////////
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// Construction/Destruction
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//////////////////////////////////////////////////////////////////////
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CSAAAmp::CSAAAmp(CSAAFreq * const ToneGenerator, const CSAANoise * const NoiseGenerator, const CSAAEnv * const EnvGenerator)
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:
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m_pcConnectedToneGenerator(ToneGenerator),
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m_pcConnectedNoiseGenerator(NoiseGenerator),
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m_pcConnectedEnvGenerator(EnvGenerator),
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m_bUseEnvelope(EnvGenerator != NULL)
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{
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leftlevel = 0;
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leftlevela0x0e = 0;
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rightlevel = 0;
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rightlevela0x0e = 0;
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m_nMixMode = 0;
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m_bMute=true;
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m_bSync = false;
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m_nOutputIntermediate=0;
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last_level_byte=0;
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SetAmpLevel(0x00);
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}
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CSAAAmp::~CSAAAmp()
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{
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// Nothing to do
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}
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void CSAAAmp::SetAmpLevel(BYTE level_byte)
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{
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// if level unchanged since last call then do nothing
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if (level_byte != last_level_byte)
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{
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last_level_byte = level_byte;
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leftlevel = level_byte & 0x0f;
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leftlevela0x0e = leftlevel & 0x0e;
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rightlevel = (level_byte >> 4) & 0x0f;
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rightlevela0x0e = rightlevel & 0x0e;
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}
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}
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void CSAAAmp::SetToneMixer(BYTE bEnabled)
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{
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if (bEnabled == 0)
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{
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// clear mixer bit
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m_nMixMode &= ~(0x01);
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}
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else
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{
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// set mixer bit
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m_nMixMode |= 0x01;
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}
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}
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void CSAAAmp::SetNoiseMixer(BYTE bEnabled)
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{
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if (bEnabled == 0)
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{
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m_nMixMode &= ~(0x02);
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}
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else
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{
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m_nMixMode |= 0x02;
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}
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}
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void CSAAAmp::Mute(bool bMute)
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{
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// m_bMute refers to the GLOBAL mute setting (register 28 bit 0)
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// NOT the per-channel mixer settings !!
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m_bMute = bMute;
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}
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void CSAAAmp::Sync(bool bSync)
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{
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// m_bSync refers to the GLOBAL sync setting (register 28 bit 1)
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m_bSync = bSync;
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}
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void CSAAAmp::Tick(void)
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{
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// updates m_nOutputIntermediate to 0, 1 or 2
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//
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// connected oscillator always ticks (this isn't really connected to the amp)
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int level = m_pcConnectedToneGenerator->Tick();
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switch (m_nMixMode)
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{
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case 0:
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// no tone or noise for this channel
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m_nOutputIntermediate = 0;
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break;
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case 1:
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// tone only for this channel
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m_nOutputIntermediate = level * 2;
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// NOTE: ConnectedToneGenerator returns either 0 or 1
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break;
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case 2:
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// noise only for this channel
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m_nOutputIntermediate = m_pcConnectedNoiseGenerator->Level() * 2;
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// NOTE: ConnectedNoiseGenerator()->Level() returns either 0 or 1
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break;
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case 3:
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// tone+noise for this channel ... mixing algorithm :
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// tone noise output
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// 0 0 0
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// 1 0 2
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// 0 1 0
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// 1 1 1
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// = 2 * tone - 1 * (tone & noise)
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// = tone * (2 - noise)
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m_nOutputIntermediate = level * (2 - m_pcConnectedNoiseGenerator->Level());
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break;
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}
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// intermediate is between 0 and 2
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}
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inline int CSAAAmp::EffectiveAmplitude(int amp, int env) const
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{
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// Return the effective amplitude of the low-pass-filtered result of the logical
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// AND of the amplitude PDM and envelope PDM patterns. This is a more accurate
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// evaluation of the SAA than simply returning amp * env , based on how the SAA
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// implements pulse-density modulation.
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static const int pdm[16][16] = {
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{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
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{0,0,0,0,2,2,2,2,2,2,2,2,4,4,4,4},
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{0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8},
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{0,1,1,2,4,5,5,6,6,7,7,8,10,11,11,12},
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{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15},
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{0,1,2,3,6,7,8,9,10,11,12,13,16,17,18,19},
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{0,2,3,5,6,8,9,11,12,14,15,17,18,20,21,23},
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{0,2,3,5,8,10,11,13,14,16,17,19,22,24,25,27},
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{0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30},
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{0,2,4,6,10,12,14,16,18,20,22,24,28,30,32,34},
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{0,3,5,8,10,13,15,18,20,23,25,28,30,33,35,38},
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{0,3,5,8,12,15,17,20,22,25,27,30,34,37,39,42},
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{0,3,6,9,12,15,18,21,24,27,30,33,36,39,42,45},
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{0,3,6,9,14,17,20,23,26,29,32,35,40,43,46,49},
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{0,4,7,11,14,18,21,25,28,32,35,39,42,46,49,53},
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{0,4,7,11,16,20,23,27,30,34,37,41,46,50,53,57}
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};
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return(pdm[amp][env] * 4);
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}
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void CSAAAmp::TickAndOutputStereo(unsigned int & left, unsigned int & right)
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{
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// This returns a value between 0 and 480 inclusive.
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// This represents the full dynamic range of one output mixer (tone, or noise+tone, at full volume,
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// without envelopes enabled). Note that, with envelopes enabled, the actual dynamic range
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// is reduced on-chip to just over 88% of this (424), so the "loudest" output requires disabling envs.
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// NB for 6 channels at full volume, with simple additive mixing, you would see a combined
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// output of 2880, and a multiplier of 11 (=31680) fits comfortably within 16-bit signed output range.
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if (m_bSync)
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{
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// TODO check this
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left = right = 0;
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return;
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}
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// first, do the Tick:
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Tick();
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// now calculate the returned amplitude for this sample:
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////////////////////////////////////////////////////////
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if (m_bMute)
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{
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left = right = 0;
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}
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else if (m_bUseEnvelope && m_pcConnectedEnvGenerator->IsActive())
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{
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left = EffectiveAmplitude(m_pcConnectedEnvGenerator->LeftLevel(), leftlevela0x0e) * (2 - m_nOutputIntermediate);
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right = EffectiveAmplitude(m_pcConnectedEnvGenerator->RightLevel(), rightlevela0x0e) * (2 - m_nOutputIntermediate);
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}
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else
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{
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left = leftlevel * m_nOutputIntermediate * 16;
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right = rightlevel * m_nOutputIntermediate * 16;
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}
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}
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