87 lines
2.2 KiB
C++
87 lines
2.2 KiB
C++
/*
|
|
* Paula.h
|
|
* -------
|
|
* Purpose: Emulating the Amiga's sound chip, Paula, by implementing resampling using band-limited steps (BLEPs)
|
|
* Notes : (currently none)
|
|
* Authors: OpenMPT Devs
|
|
* Antti S. Lankila
|
|
* The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include "BuildSettings.h"
|
|
|
|
#include "Snd_defs.h"
|
|
#include "Mixer.h"
|
|
|
|
OPENMPT_NAMESPACE_BEGIN
|
|
|
|
namespace Paula
|
|
{
|
|
|
|
inline constexpr int PAULA_HZ = 3546895;
|
|
inline constexpr int MINIMUM_INTERVAL = 4; // Tradeoff between quality and speed (lower = less aliasing)
|
|
inline constexpr int BLEP_SCALE = 17; // TODO: Should be 1 for float mixer
|
|
inline constexpr int BLEP_SIZE = 2048;
|
|
|
|
using BlepArray = std::array<mixsample_t, BLEP_SIZE>;
|
|
|
|
|
|
class BlepTables
|
|
{
|
|
enum AmigaFilter
|
|
{
|
|
A500Off = 0,
|
|
A500On,
|
|
A1200Off,
|
|
A1200On,
|
|
Unfiltered,
|
|
NumFilterTypes
|
|
};
|
|
|
|
std::array<Paula::BlepArray, AmigaFilter::NumFilterTypes> WinSincIntegral;
|
|
|
|
public:
|
|
void InitTables();
|
|
const Paula::BlepArray &GetAmigaTable(Resampling::AmigaFilter amigaType, bool enableFilter) const;
|
|
};
|
|
|
|
|
|
class State
|
|
{
|
|
// MAX_BLEPS configures how many BLEPs (volume steps) are being kept track of per channel,
|
|
// and thus directly influences how much memory this feature wastes per virtual channel.
|
|
// Paula::BLEP_SIZE / Paula::MINIMUM_INTERVAL would be a safe maximum,
|
|
// but even a sample (alternating at +1/-1, thus causing a step on every frame) played at 200 kHz,
|
|
// which is way out of spec for the Amiga, will only get close to 128 active BLEPs with Paula::MINIMUM_INTERVAL == 4.
|
|
// Hence 128 is chosen as a tradeoff between quality and memory consumption.
|
|
static constexpr uint16 MAX_BLEPS = 128;
|
|
|
|
struct Blep
|
|
{
|
|
int16 level;
|
|
uint16 age;
|
|
};
|
|
|
|
public:
|
|
SamplePosition remainder, stepRemainder;
|
|
int numSteps; // Number of full-length steps
|
|
private:
|
|
uint16 activeBleps = 0, firstBlep = 0; // Count of simultaneous bleps to keep track of
|
|
int16 globalOutputLevel = 0; // The instantenous value of Paula output
|
|
Blep blepState[MAX_BLEPS];
|
|
|
|
public:
|
|
State(uint32 sampleRate = 48000);
|
|
|
|
void Reset();
|
|
void InputSample(int16 sample);
|
|
int OutputSample(const BlepArray &WinSincIntegral);
|
|
void Clock(int cycles);
|
|
};
|
|
|
|
}
|
|
|
|
OPENMPT_NAMESPACE_END
|