Update residfp to newer build
Co-Authored-By: Alexander Babikov <2708460+lemondrops@users.noreply.github.com>
This commit is contained in:
Jasmine Iwanek
419
src/sound/resid-fp/EnvelopeGenerator.h
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419
src/sound/resid-fp/EnvelopeGenerator.h
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/*
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* This file is part of libsidplayfp, a SID player engine.
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*
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* Copyright 2011-2022 Leandro Nini <drfiemost@users.sourceforge.net>
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* Copyright 2018 VICE Project
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* Copyright 2007-2010 Antti Lankila
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* Copyright 2004,2010 Dag Lem <resid@nimrod.no>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at 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,
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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. See the
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* GNU General Public License for more details.
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*
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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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef ENVELOPEGENERATOR_H
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#define ENVELOPEGENERATOR_H
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#include "siddefs-fp.h"
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namespace reSIDfp
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{
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/**
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* A 15 bit [LFSR] is used to implement the envelope rates, in effect dividing
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* the clock to the envelope counter by the currently selected rate period.
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*
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* In addition, another 5 bit counter is used to implement the exponential envelope decay,
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* in effect further dividing the clock to the envelope counter.
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* The period of this counter is set to 1, 2, 4, 8, 16, 30 at the envelope counter
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* values 255, 93, 54, 26, 14, 6, respectively.
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*
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* [LFSR]: https://en.wikipedia.org/wiki/Linear_feedback_shift_register
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*/
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class EnvelopeGenerator
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{
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private:
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/**
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* The envelope state machine's distinct states. In addition to this,
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* envelope has a hold mode, which freezes envelope counter to zero.
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*/
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enum State
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{
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ATTACK, DECAY_SUSTAIN, RELEASE
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};
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private:
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/// XOR shift register for ADSR prescaling.
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unsigned int lfsr;
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/// Comparison value (period) of the rate counter before next event.
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unsigned int rate;
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/**
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* During release mode, the SID approximates envelope decay via piecewise
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* linear decay rate.
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*/
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unsigned int exponential_counter;
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/**
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* Comparison value (period) of the exponential decay counter before next
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* decrement.
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*/
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unsigned int exponential_counter_period;
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unsigned int new_exponential_counter_period;
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unsigned int state_pipeline;
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///
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unsigned int envelope_pipeline;
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unsigned int exponential_pipeline;
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/// Current envelope state
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State state;
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State next_state;
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/// Whether counter is enabled. Only switching to ATTACK can release envelope.
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bool counter_enabled;
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/// Gate bit
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bool gate;
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///
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bool resetLfsr;
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/// The current digital value of envelope output.
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unsigned char envelope_counter;
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/// Attack register
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unsigned char attack;
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/// Decay register
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unsigned char decay;
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/// Sustain register
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unsigned char sustain;
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/// Release register
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unsigned char release;
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/// The ENV3 value, sampled at the first phase of the clock
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unsigned char env3;
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private:
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static const unsigned int adsrtable[16];
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private:
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void set_exponential_counter();
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void state_change();
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public:
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/**
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* SID clocking.
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*/
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void clock();
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/**
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* Get the Envelope Generator digital output.
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*/
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unsigned int output() const { return envelope_counter; }
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/**
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* Constructor.
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*/
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EnvelopeGenerator() :
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lfsr(0x7fff),
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rate(0),
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exponential_counter(0),
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exponential_counter_period(1),
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new_exponential_counter_period(0),
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state_pipeline(0),
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envelope_pipeline(0),
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exponential_pipeline(0),
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state(RELEASE),
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next_state(RELEASE),
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counter_enabled(true),
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gate(false),
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resetLfsr(false),
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envelope_counter(0xaa),
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attack(0),
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decay(0),
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sustain(0),
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release(0),
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env3(0)
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{}
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/**
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* SID reset.
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*/
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void reset();
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/**
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* Write control register.
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*
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* @param control
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* control register value
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*/
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void writeCONTROL_REG(unsigned char control);
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/**
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* Write Attack/Decay register.
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*
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* @param attack_decay
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* attack/decay value
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*/
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void writeATTACK_DECAY(unsigned char attack_decay);
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/**
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* Write Sustain/Release register.
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*
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* @param sustain_release
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* sustain/release value
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*/
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void writeSUSTAIN_RELEASE(unsigned char sustain_release);
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/**
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* Return the envelope current value.
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*
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* @return envelope counter value
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*/
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unsigned char readENV() const { return env3; }
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};
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} // namespace reSIDfp
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#if RESID_INLINING || defined(ENVELOPEGENERATOR_CPP)
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namespace reSIDfp
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{
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RESID_INLINE
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void EnvelopeGenerator::clock()
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{
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env3 = envelope_counter;
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if (unlikely(new_exponential_counter_period > 0))
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{
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exponential_counter_period = new_exponential_counter_period;
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new_exponential_counter_period = 0;
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}
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if (unlikely(state_pipeline))
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{
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state_change();
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}
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if (unlikely(envelope_pipeline != 0) && (--envelope_pipeline == 0))
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{
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if (likely(counter_enabled))
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{
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if (state == ATTACK)
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{
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if (++envelope_counter==0xff)
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{
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next_state = DECAY_SUSTAIN;
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state_pipeline = 3;
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}
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}
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else if ((state == DECAY_SUSTAIN) || (state == RELEASE))
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{
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if (--envelope_counter==0x00)
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{
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counter_enabled = false;
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}
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}
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set_exponential_counter();
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}
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}
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else if (unlikely(exponential_pipeline != 0) && (--exponential_pipeline == 0))
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{
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exponential_counter = 0;
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if (((state == DECAY_SUSTAIN) && (envelope_counter != sustain))
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|| (state == RELEASE))
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{
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// The envelope counter can flip from 0x00 to 0xff by changing state to
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// attack, then to release. The envelope counter will then continue
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// counting down in the release state.
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// This has been verified by sampling ENV3.
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envelope_pipeline = 1;
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}
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}
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else if (unlikely(resetLfsr))
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{
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lfsr = 0x7fff;
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resetLfsr = false;
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if (state == ATTACK)
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{
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// The first envelope step in the attack state also resets the exponential
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// counter. This has been verified by sampling ENV3.
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exponential_counter = 0; // NOTE this is actually delayed one cycle, not modeled
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// The envelope counter can flip from 0xff to 0x00 by changing state to
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// release, then to attack. The envelope counter is then frozen at
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// zero; to unlock this situation the state must be changed to release,
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// then to attack. This has been verified by sampling ENV3.
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envelope_pipeline = 2;
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}
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else
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{
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if (counter_enabled && (++exponential_counter == exponential_counter_period))
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exponential_pipeline = exponential_counter_period != 1 ? 2 : 1;
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}
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}
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// ADSR delay bug.
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// If the rate counter comparison value is set below the current value of the
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// rate counter, the counter will continue counting up until it wraps around
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// to zero at 2^15 = 0x8000, and then count rate_period - 1 before the
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// envelope can constly be stepped.
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// This has been verified by sampling ENV3.
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// check to see if LFSR matches table value
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if (likely(lfsr != rate))
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{
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// it wasn't a match, clock the LFSR once
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// by performing XOR on last 2 bits
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const unsigned int feedback = ((lfsr << 14) ^ (lfsr << 13)) & 0x4000;
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lfsr = (lfsr >> 1) | feedback;
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}
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else
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{
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resetLfsr = true;
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}
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}
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/**
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* This is what happens on chip during state switching,
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* based on die reverse engineering and transistor level
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* emulation.
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*
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* Attack
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*
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* 0 - Gate on
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* 1 - Counting direction changes
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* During this cycle the decay rate is "accidentally" activated
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* 2 - Counter is being inverted
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* Now the attack rate is correctly activated
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* Counter is enabled
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* 3 - Counter will be counting upward from now on
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*
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* Decay
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*
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* 0 - Counter == $ff
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* 1 - Counting direction changes
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* The attack state is still active
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* 2 - Counter is being inverted
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* During this cycle the decay state is activated
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* 3 - Counter will be counting downward from now on
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*
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* Release
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*
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* 0 - Gate off
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* 1 - During this cycle the release state is activated if coming from sustain/decay
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* *2 - Counter is being inverted, the release state is activated
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* *3 - Counter will be counting downward from now on
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*
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* (* only if coming directly from Attack state)
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*
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* Freeze
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*
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* 0 - Counter == $00
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* 1 - Nothing
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* 2 - Counter is disabled
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*/
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RESID_INLINE
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void EnvelopeGenerator::state_change()
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{
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state_pipeline--;
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switch (next_state)
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{
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case ATTACK:
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if (state_pipeline == 1)
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{
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// The decay rate is "accidentally" enabled during first cycle of attack phase
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rate = adsrtable[decay];
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}
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else if (state_pipeline == 0)
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{
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state = ATTACK;
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// The attack rate is correctly enabled during second cycle of attack phase
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rate = adsrtable[attack];
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counter_enabled = true;
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}
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break;
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case DECAY_SUSTAIN:
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if (state_pipeline == 0)
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{
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state = DECAY_SUSTAIN;
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rate = adsrtable[decay];
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}
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break;
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case RELEASE:
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if (((state == ATTACK) && (state_pipeline == 0))
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|| ((state == DECAY_SUSTAIN) && (state_pipeline == 1)))
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{
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state = RELEASE;
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rate = adsrtable[release];
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}
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break;
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}
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}
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RESID_INLINE
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void EnvelopeGenerator::set_exponential_counter()
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{
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// Check for change of exponential counter period.
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//
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// For a detailed description see:
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// http://ploguechipsounds.blogspot.it/2010/03/sid-6581r3-adsr-tables-up-close.html
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switch (envelope_counter)
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{
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case 0xff:
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case 0x00:
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new_exponential_counter_period = 1;
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break;
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case 0x5d:
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new_exponential_counter_period = 2;
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break;
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case 0x36:
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new_exponential_counter_period = 4;
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break;
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case 0x1a:
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new_exponential_counter_period = 8;
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break;
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case 0x0e:
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new_exponential_counter_period = 16;
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break;
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case 0x06:
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new_exponential_counter_period = 30;
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break;
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}
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}
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} // namespace reSIDfp
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#endif
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#endif
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