Applied the recent mainline PCem commits (and fixed the Pentium machines);
Ported the Roland MT-32 emulation (using MUNT) from bit's MT32 emulation branch of PCem; Sanitized the OpenAL give buffer code in openal.c a bit; NVR path is now specifiable in the Settings dialog; Added Logitech 3-button serial mouse per protocol description by waltje; The RTL8029AS and the BT-958D now actually use the PCI IRQ routing; Fixed BT-958D PCI device initialization on the bus; PCI IRQ routing now respects the edge/level setting set on ports 4D0/4D1.
This commit is contained in:
OBattler
155
src/SOUND/munt/LA32Ramp.cpp
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155
src/SOUND/munt/LA32Ramp.cpp
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/* Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009 Dean Beeler, Jerome Fisher
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* Copyright (C) 2011-2017 Dean Beeler, Jerome Fisher, Sergey V. Mikayev
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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 Lesser General Public License as published by
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* the Free Software Foundation, either version 2.1 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 Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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Some notes on this class:
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This emulates the LA-32's implementation of "ramps". A ramp in this context is a smooth transition from one value to another, handled entirely within the LA-32.
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The LA-32 provides this feature for amplitude and filter cutoff values.
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The 8095 starts ramps on the LA-32 by setting two values in memory-mapped registers:
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(1) The target value (between 0 and 255) for the ramp to end on. This is represented by the "target" argument to startRamp().
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(2) The speed at which that value should be approached. This is represented by the "increment" argument to startRamp().
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Once the ramp target value has been hit, the LA-32 raises an interrupt.
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Note that the starting point of the ramp is whatever internal value the LA-32 had when the registers were set. This is usually the end point of a previously completed ramp.
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Our handling of the "target" and "increment" values is based on sample analysis and a little guesswork.
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Here's what we're pretty confident about:
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- The most significant bit of "increment" indicates the direction that the LA32's current internal value ("current" in our emulation) should change in.
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Set means downward, clear means upward.
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- The lower 7 bits of "increment" indicate how quickly "current" should be changed.
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- If "increment" is 0, no change to "current" is made and no interrupt is raised. [SEMI-CONFIRMED by sample analysis]
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- Otherwise, if the MSb is set:
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- If "current" already corresponds to a value <= "target", "current" is set immediately to the equivalent of "target" and an interrupt is raised.
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- Otherwise, "current" is gradually reduced (at a rate determined by the lower 7 bits of "increment"), and once it reaches the equivalent of "target" an interrupt is raised.
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- Otherwise (the MSb is unset):
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- If "current" already corresponds to a value >= "target", "current" is set immediately to the equivalent of "target" and an interrupt is raised.
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- Otherwise, "current" is gradually increased (at a rate determined by the lower 7 bits of "increment"), and once it reaches the equivalent of "target" an interrupt is raised.
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We haven't fully explored:
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- Values when ramping between levels (though this is probably correct).
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- Transition timing (may not be 100% accurate, especially for very fast ramps).
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*/
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#include "internals.h"
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#include "LA32Ramp.h"
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#include "Tables.h"
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namespace MT32Emu {
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// SEMI-CONFIRMED from sample analysis.
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const int TARGET_MULT = 0x40000;
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const unsigned int MAX_CURRENT = 0xFF * TARGET_MULT;
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// We simulate the delay in handling "target was reached" interrupts by waiting
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// this many samples before setting interruptRaised.
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// FIXME: This should vary with the sample rate, but doesn't.
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// SEMI-CONFIRMED: Since this involves asynchronous activity between the LA32
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// and the 8095, a good value is hard to pin down.
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// This one matches observed behaviour on a few digital captures I had handy,
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// and should be double-checked. We may also need a more sophisticated delay
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// scheme eventually.
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const int INTERRUPT_TIME = 7;
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LA32Ramp::LA32Ramp() :
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current(0),
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largeTarget(0),
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largeIncrement(0),
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interruptCountdown(0),
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interruptRaised(false) {
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}
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void LA32Ramp::startRamp(Bit8u target, Bit8u increment) {
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// CONFIRMED: From sample analysis, this appears to be very accurate.
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if (increment == 0) {
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largeIncrement = 0;
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} else {
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// Three bits in the fractional part, no need to interpolate
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// (unsigned int)(EXP2F(((increment & 0x7F) + 24) / 8.0f) + 0.125f)
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Bit32u expArg = increment & 0x7F;
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largeIncrement = 8191 - Tables::getInstance().exp9[~(expArg << 6) & 511];
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largeIncrement <<= expArg >> 3;
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largeIncrement += 64;
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largeIncrement >>= 9;
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}
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descending = (increment & 0x80) != 0;
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if (descending) {
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// CONFIRMED: From sample analysis, descending increments are slightly faster
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largeIncrement++;
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}
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largeTarget = target * TARGET_MULT;
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interruptCountdown = 0;
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interruptRaised = false;
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}
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Bit32u LA32Ramp::nextValue() {
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if (interruptCountdown > 0) {
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if (--interruptCountdown == 0) {
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interruptRaised = true;
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}
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} else if (largeIncrement != 0) {
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// CONFIRMED from sample analysis: When increment is 0, the LA32 does *not* change the current value at all (and of course doesn't fire an interrupt).
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if (descending) {
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// Lowering current value
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if (largeIncrement > current) {
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current = largeTarget;
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interruptCountdown = INTERRUPT_TIME;
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} else {
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current -= largeIncrement;
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if (current <= largeTarget) {
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current = largeTarget;
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interruptCountdown = INTERRUPT_TIME;
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}
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}
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} else {
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// Raising current value
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if (MAX_CURRENT - current < largeIncrement) {
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current = largeTarget;
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interruptCountdown = INTERRUPT_TIME;
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} else {
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current += largeIncrement;
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if (current >= largeTarget) {
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current = largeTarget;
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interruptCountdown = INTERRUPT_TIME;
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}
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}
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}
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}
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return current;
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}
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bool LA32Ramp::checkInterrupt() {
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bool wasRaised = interruptRaised;
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interruptRaised = false;
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return wasRaised;
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}
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void LA32Ramp::reset() {
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current = 0;
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largeTarget = 0;
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largeIncrement = 0;
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descending = false;
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interruptCountdown = 0;
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interruptRaised = false;
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}
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} // namespace MT32Emu
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