381 lines
12 KiB
C++
Executable file
381 lines
12 KiB
C++
Executable file
// Part of SAASound copyright 1998-2018 Dave Hooper <dave@beermex.com>
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//
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// SAAEnv.cpp: implementation of the CSAAEnv class.
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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 "SAAEnv.h"
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//////////////////////////////////////////////////////////////////////
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// Static member initialisation
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//////////////////////////////////////////////////////////////////////
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const ENVDATA CSAAEnv::cs_EnvData[8] =
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{
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{1,false, { {{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}},
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{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}}},
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{1,true, { {{15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15},{15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15}},
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{{14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14},{14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14}}}},
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{1,false, { {{15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}},
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{{14,14,12,12,10,10,8,8,6,6,4,4,2,2,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}}},
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{1,true, { {{15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}},
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{{14,14,12,12,10,10,8,8,6,6,4,4,2,2,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}}},
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{2,false, { {{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}, {15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0}},
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{{0,0,2,2,4,4,6,6,8,8,10,10,12,12,14,14}, {14,14,12,12,10,10,8,8,6,6,4,4,2,2,0,0}}}},
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{2,true, { {{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}, {15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0}},
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{{0,0,2,2,4,4,6,6,8,8,10,10,12,12,14,14}, {14,14,12,12,10,10,8,8,6,6,4,4,2,2,0,0}}}},
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{1,false, { {{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}},
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{{0,0,2,2,4,4,6,6,8,8,10,10,12,12,14,14}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}}},
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{1,true, { {{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}},
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{{0,0,2,2,4,4,6,6,8,8,10,10,12,12,14,14}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}}}}
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};
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//////////////////////////////////////////////////////////////////////
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// Construction/Destruction
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//////////////////////////////////////////////////////////////////////
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CSAAEnv::CSAAEnv()
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:
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m_bEnabled(false),
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m_nPhase(0),
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m_nPhasePosition(0),
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m_bEnvelopeEnded(true),
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m_nResolution(1),
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m_bNewData(false),
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m_nNextData(0)
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{
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// initialise itself with the value 'zero'
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SetEnvControl(0);
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}
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CSAAEnv::~CSAAEnv()
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{
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// Nothing to do
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}
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void CSAAEnv::InternalClock(void)
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{
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// will only do something if envelope clock mode is set to internal
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// and the env control is enabled
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if (m_bEnabled && (!m_bClockExternally)) Tick();
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}
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void CSAAEnv::ExternalClock(void)
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{
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// will only do something if envelope clock mode is set to external
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// and the env control is enabled
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if (m_bClockExternally && m_bEnabled) Tick();
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}
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void CSAAEnv::SetEnvControl(int nData)
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{
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// process immediate stuff first:
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// start with the Enabled flag. if env is disabled,
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// there's not much to do
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bool bEnabled = ((nData & 0x80)==0x80);
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if (!bEnabled && !m_bEnabled)
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return;
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m_bEnabled = bEnabled;
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if (!m_bEnabled)
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{
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// env control was enabled, and now disabled
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// Any subsequent env control changes are immediate.
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m_bEnvelopeEnded = true;
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return;
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}
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// Resolution (3bit/4bit) is also immediately processed
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int new_resolution = ((nData & 0x10) == 0x10) ? 2 : 1;
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// NOTE: undocumented behaviour when changing resolution mid-waveform
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// Empirically, the following matches observations:
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// * When ticking the env generator with 4-bit resolution, the position += 1
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// * When ticking the env generator with 3-bit resolution, the position += 2
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// * When changing between 4-bit resolution and 3-bit resolution
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// without ticking the env generator, the position is unchanged
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// (although, effectively, the LSB is ignored. Purely as an implementation
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// detail, I'm implementing this as clearing the LSB ie LSB=0; see next point)
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// * When changing between 3-bit resolution and 4-bit resolution
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// without ticking the env generator, the position LSB is set to 1
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// See test case: envext_34b
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//
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if (m_nResolution == 1 && new_resolution == 2)
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{
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// change from 4-bit to 3-bit
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m_nPhasePosition &= 0xe;
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}
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else if (m_nResolution == 2 && new_resolution == 1)
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{
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// change from 3-bit to 4-bit
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m_nPhasePosition |= 0x1;
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}
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m_nResolution = new_resolution;
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// now buffered stuff: but only if it's ok to, and only if the
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// envgenerator is not disabled. otherwise it just stays buffered until
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// the Tick() function sets m_bEnvelopeEnded to true and realises there is
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// already some new data waiting
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if (m_bEnvelopeEnded)
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{
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SetNewEnvData(nData); // also does the SetLevels() call for us.
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m_bNewData=false;
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}
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else
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{
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// since the 'next resolution' changes arrive unbuffered, we
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// may need to change the current level because of this:
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SetLevels();
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// store current new data, and set the newdata flag:
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m_bNewData = true;
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m_nNextData = nData;
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}
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}
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int CSAAEnv::LeftLevel(void) const
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{
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return m_nLeftLevel;
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}
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int CSAAEnv::RightLevel(void) const
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{
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return m_nRightLevel;
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}
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inline void CSAAEnv::Tick(void)
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{
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// if disabled, do nothing
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if (!m_bEnabled) // m_bEnabled is set directly, not buffered, so this is ok
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{
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// for sanity, reset stuff:
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m_bEnvelopeEnded = true;
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m_nPhase = 0;
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m_nPhasePosition = 0;
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return;
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}
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// else : m_bEnabled
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if (m_bEnvelopeEnded)
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{
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// do nothing
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// (specifically, don't change the values of m_bEnvelopeEnded,
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// m_nPhase and m_nPhasePosition, as these will still be needed
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// by SetLevels() should it be called again)
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return;
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}
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// else : !m_bEnvelopeEnded
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// Continue playing the same envelope ...
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// increments the phaseposition within an envelope.
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// also handles looping and resolution appropriately.
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// Changes the level of the envelope accordingly
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// through calling SetLevels() . This must be called after making
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// any changes that will affect the output levels of the env controller!!
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// SetLevels also handles left-right channel inverting
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// increment phase position
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m_nPhasePosition += m_nResolution;
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// if this means we've gone past 16 (the end of a phase)
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// then change phase, and if necessary, loop
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// Refer to datasheet for meanings of (3) and (4) in following text
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// w.r.t SAA1099 envelopes
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// Note that we will always reach position (3) or (4), even if we keep toggling
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// resolution from 4-bit to 3-bit and back, because the counter will always wrap to 0.
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// In fact it's quite elegant:
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// No matter how you increment and toggle and increment and toggle, the counter
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// will at some point be either 0xe (either 4-bit mode or 3-bit mode) or 0xf (4-bit mode only).
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// Depending on the mode, even if you change the mode, the next increment,
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// or the one after it, will then take it to 0.
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// 0xe + 2 (3bit mode) => 0x0
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// 0xe + 1 (4bit mode) => 0xf
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// 0xf + 1 (4bit mode) => 0x0
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// 0xe -> (toggle 3bit mode to 4bit mode) => 0xf
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// 0xe -> (toggle 4bit mode to 3bit mode) => 0xe
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// 0xf -> (toggle 4bit mode to 3bit mode) => 0xe
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//
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// but there is a subtlety (of course), which is that any changes at point (3)
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// can take place immediately you hit point (3), but changes at point (4) are actually
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// only acted upon when the counter transitions from 0xe (or 0xf) to 0x0 (which also
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// means that, for these looping envelopes, which are the ones that have a point(4),
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// immediately after the counter wrapping to 0x0, a write to the env data register will
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// NOT set the waveform and will NOT reset the phase/phaseposition (even though it
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// will still let you toggle the 4bit/3bit mode, which will change the phaseposition LSB!)
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// See test case: envext_34c
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bool bProcessNewDataIfAvailable = false;
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if (m_nPhasePosition >= 16)
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{
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m_nPhase++;
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// if we should loop, then do so - and we've reached position (4)
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// otherwise, if we shouldn't loop,
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// then we've reached position (3) and so we say that
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// we're ok for new data.
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if (m_nPhase == m_nNumberOfPhases)
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{
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// at position (3) or (4)
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if (!m_bLooping)
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{
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// position (3) only
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// note that it seems that the sustain level is ALWAYS zero
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// in the case of non-looping waveforms
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m_bEnvelopeEnded = true;
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bProcessNewDataIfAvailable = true;
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}
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else
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{
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// position (4) only
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// note that any data already latched is ONLY acted upon
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// at THIS point. If (after this Tick has completed) any new
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// env data is written, it will NOT be acted upon, until
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// we get back to position (4) again.
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// this is why m_bEnvelopeEnded (which affects the behaviour
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// of the SetEnvControl method) is FALSE here.
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// See test case: envext_34c (as noted earlier)
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m_bEnvelopeEnded = false;
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// set phase pointer to start of envelope for loop
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// and reset m_nPhasePosition
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m_nPhase=0;
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m_nPhasePosition -= 16;
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bProcessNewDataIfAvailable = true;
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}
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}
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else // (m_nPhase < m_nNumberOfPhases)
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{
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// not at position (3) or (4) ...
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// (i.e., we're in the middle of an envelope with
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// more than one phase. Specifically, we're in
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// the middle of envelope 4 or 5 - the
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// triangle envelopes - but that's not important)
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// any commands sent to this envelope controller
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// will be buffered. Set the flag to indicate this.
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m_bEnvelopeEnded = false;
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m_nPhasePosition -= 16;
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}
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}
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else // (m_nPhasePosition < 16)
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{
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// still within the same phase;
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// but, importantly, we are no longer at the start of the phase ...
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// so new data cannot be acted on immediately, and must
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// be buffered
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m_bEnvelopeEnded = false;
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// Phase and PhasePosition have already been updated.
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// SetLevels() will need to be called to actually calculate
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// the output 'level' of this envelope controller
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}
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// if we have new (buffered) data, now is the time to act on it
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if (m_bNewData && bProcessNewDataIfAvailable)
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{
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m_bNewData = false;
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SetNewEnvData(m_nNextData);
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}
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else
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{
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// ok, we didn't have any new buffered date to act on,
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// so we just call SetLevels() to calculate the output level
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// for whatever the current envelope is
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SetLevels();
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}
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}
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inline void CSAAEnv::SetLevels(void)
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{
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// sets m_nLeftLevel
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// Also sets m_nRightLevel in terms of m_nLeftLevel
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// and m_bInvertRightChannel
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// m_nResolution: 1 means 4-bit resolution; 2 means 3-bit resolution. Resolution of envelope waveform.
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// Note that this is handled 'immediately', and doesn't wait for synchronisation of
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// the envelope waveform (this is important, see test case EnvExt_imm)
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// It is therefore possible to switch between 4-bit and 3-bit resolution in the middle of
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// an envelope waveform. if you are at an 'odd' phase position, you would be able to hear
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// the difference. if you are at an 'even' phase position, the volume level for 4-bit
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// and 3-bit would be the same.
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// NOTE: additional test cases are required.
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switch (m_nResolution)
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{
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case 1: // 4 bit res waveforms
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default:
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{
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// special case: if envelope is not a looping one, and we're at the end
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// then our level should be zero (all of the non-looping waveforms have
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// a sustain level of zero):
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if (m_bEnvelopeEnded && !m_bLooping)
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m_nLeftLevel = 0;
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else
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m_nLeftLevel = m_pEnvData->nLevels[0][m_nPhase][m_nPhasePosition];
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if (m_bInvertRightChannel)
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m_nRightLevel = 15-m_nLeftLevel;
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else
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m_nRightLevel = m_nLeftLevel;
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break;
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}
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case 2: // 3 bit res waveforms
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{
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// special case: if envelope is not a looping one, and we're at the end
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// then our level should be zero (all of the non-looping waveforms have
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// a sustain level of zero):
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if (m_bEnvelopeEnded && !m_bLooping)
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m_nLeftLevel = 0;
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else
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m_nLeftLevel = m_pEnvData->nLevels[1][m_nPhase][m_nPhasePosition];
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if (m_bInvertRightChannel)
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m_nRightLevel = 14-m_nLeftLevel;
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else
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m_nRightLevel = m_nLeftLevel;
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break;
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}
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}
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}
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inline void CSAAEnv::SetNewEnvData(int nData)
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{
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// loads envgenerator's registers according to the bits set
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// in nData
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m_nPhase = 0;
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m_nPhasePosition = 0;
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m_pEnvData = &(cs_EnvData[(nData >> 1) & 0x07]);
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m_bInvertRightChannel = ((nData & 0x01) == 0x01);
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m_bClockExternally = ((nData & 0x20) == 0x20);
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m_nNumberOfPhases = m_pEnvData->nNumberOfPhases;
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m_bLooping = m_pEnvData->bLooping;
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m_nResolution = (((nData & 0x10)==0x10) ? 2 : 1);
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m_bEnabled = ((nData & 0x80) == 0x80);
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if (m_bEnabled)
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{
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m_bEnvelopeEnded = false;
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// is this right?
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// YES. See test case EnvExt_34c (setting data multiple times
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// when at a point (3) resets the waveform so you're no longer
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// at a point (3).
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}
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else
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{
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// DISABLED - so set stuff accordingly
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m_bEnvelopeEnded = true;
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m_nPhase = 0;
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m_nPhasePosition = 0;
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}
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SetLevels();
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}
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