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Taud: Amiga interpolation mode and LPF toggle

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minjaesong
2026-05-09 16:04:57 +09:00
parent 9f01bdfee9
commit bc235ebb17
5 changed files with 189 additions and 24 deletions
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188
tsvm_core/src/net/torvald/tsvm/peripheral/AudioAdapter.kt
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@@ -18,6 +18,7 @@ import kotlin.math.roundToInt
import kotlin.math.PI
import kotlin.math.cos
import kotlin.math.sin
import kotlin.math.exp
private class RenderRunnable(val playhead: AudioAdapter.Playhead) : Runnable {
private fun printdbg(msg: Any) {
@@ -151,6 +152,70 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
const val SAMPLE_BANK_COUNT: Int = 16 // 16 × 512 K = 8 MB
const val SAMPLE_BIN_TOTAL: Long = SAMPLE_BANK_SIZE * SAMPLE_BANK_COUNT
const val SAMPLE_BANK_MASK: Int = SAMPLE_BANK_COUNT - 1
// Interpolation modes (TAUD_NOTE_EFFECTS.md §1, bits 2-3 of global behaviour flags).
// 0 = default (Fast Sinc, 16-tap windowed sinc), 1 = none (zero-order hold),
// 2 = Amiga 500 (ZOH + A500 1-pole LPF), 3 = Amiga 1200 (ZOH + A1200 LPF — bypassed).
// Amiga modes additionally apply a 2-pole Sallen-Key "LED" LPF when ts.ledFilterOn,
// which is toggled by S $0000 / S $0100 (TAUD_NOTE_EFFECTS.md §"S $0x00").
const val INTERP_DEFAULT = 0
const val INTERP_NONE = 1
const val INTERP_A500 = 2
const val INTERP_A1200 = 3
// Fast Sinc — 16-tap windowed sinc with 1024 sub-sample positions.
// Mirrors MilkyTracker's MIXER_SINCTABLE (ResamplerSinc.h: WIDTH=8, 1024-step table,
// window = 0.5 + 0.5·cos(πi / WIDTH·step)). Coefficients are symmetric so we only
// store half the kernel; the second half is index-mirrored at lookup time.
const val SINC_WIDTH = 8
const val SINC_PRECISION_SHIFT = 10
const val SINC_PRECISION = 1 shl SINC_PRECISION_SHIFT // 1024
private val SINC_TABLE: DoubleArray = run {
val n = SINC_PRECISION * SINC_WIDTH
val out = DoubleArray(n)
val winFreq = PI / SINC_WIDTH / SINC_PRECISION
out[0] = 1.0
for (i in 1 until n) {
val t = i * PI / SINC_PRECISION
val win = 0.5 + 0.5 * cos(winFreq * i)
out[i] = sin(t) / t * win
}
out
}
/** Windowed-sinc kernel value for fractional offset `frac ∈ [0,1)` and signed tap [−WIDTH+1, WIDTH]. */
private fun sincTap(frac: Double, tap: Int): Double {
val x = (tap - frac) * SINC_PRECISION // distance in sub-sample units
val ax = kotlin.math.abs(x)
val idx = ax.toInt()
if (idx >= SINC_PRECISION * SINC_WIDTH - 1) return 0.0
// Linear interpolation between adjacent table entries for sub-sub-sample precision.
val f = ax - idx
return SINC_TABLE[idx] * (1.0 - f) + SINC_TABLE[idx + 1] * f
}
// Amiga filter coefficients (precomputed at SAMPLING_RATE = 32 kHz, see pt2_paula.c
// and pt2_rcfilters.c). All filters operate on the post-mix stereo bus per playhead.
//
// A500_LP : 1-pole RC LPF, R = 360 Ω, C = 0.1 µF → fc ≈ 4420.97 Hz
// LED_LP : 2-pole Sallen-Key, R1=R2=10 kΩ, C1=6800 pF, C2=3900 pF
// → fc ≈ 3090.53 Hz, Q ≈ 0.660225
// A1200_LP: cutoff ~34.4 kHz, well above Nyquist at 32 kHz → bypassed (matches pt2-clone).
private val AMIGA_A500_LP_FC = 4420.971
private val AMIGA_LED_FC = 3090.533
private val AMIGA_LED_Q = 0.660225
// 1-pole coefficients (Direct Form II) for A500 LPF.
val AMIGA_A500_B1: Double = exp(-2.0 * PI * AMIGA_A500_LP_FC / SAMPLING_RATE)
val AMIGA_A500_A0: Double = 1.0 - AMIGA_A500_B1
// 2-pole biquad coefficients (musicdsp.org #38) for LED Sallen-Key LPF.
private val AMIGA_LED_A_BASE = 1.0 / kotlin.math.tan(PI * AMIGA_LED_FC / SAMPLING_RATE)
private val AMIGA_LED_B_BASE = 1.0 / AMIGA_LED_Q
val AMIGA_LED_A1: Double = 1.0 / (1.0 + AMIGA_LED_B_BASE * AMIGA_LED_A_BASE + AMIGA_LED_A_BASE * AMIGA_LED_A_BASE)
val AMIGA_LED_A2: Double = 2.0 * AMIGA_LED_A1
val AMIGA_LED_B1: Double = 2.0 * (1.0 - AMIGA_LED_A_BASE * AMIGA_LED_A_BASE) * AMIGA_LED_A1
val AMIGA_LED_B2: Double = (1.0 - AMIGA_LED_B_BASE * AMIGA_LED_A_BASE + AMIGA_LED_A_BASE * AMIGA_LED_A_BASE) * AMIGA_LED_A1
}
// Memory map (terranmon.txt:1985-1997, updated 2026-05-08):
@@ -1629,32 +1694,54 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
return pitchDelta
}
private fun fetchTrackerSample(voice: Voice, inst: TaudInst): Double {
/**
* Read one PCM sample (in [-1, 1]) at integer index [idx], honouring the instrument's
* funk-repeat mask. Out-of-range indices are clamped to the sample bounds; the
* caller is responsible for wrapping into a loop region first if loop semantics apply.
*/
private fun readSamplePoint(inst: TaudInst, idx: Int, sampleLen: Int, binMax: Int): Double {
val i = idx.coerceIn(0, sampleLen - 1)
var b = sampleBin[(inst.samplePtr + i).coerceAtMost(binMax).toLong()].toUint()
if (inst.funkMask != null && inst.sampleLoopEnd > inst.sampleLoopStart) {
val ls = inst.sampleLoopStart
if (i in ls until inst.sampleLoopEnd && inst.funkBit(i - ls)) b = b xor 0xFF
}
return (b - 127.5) / 127.5
}
private fun fetchTrackerSample(voice: Voice, inst: TaudInst, interpMode: Int): Double {
if (inst.index == 0) return 0.0
val basePtr = inst.samplePtr
val sampleLen = inst.sampleLength.coerceAtLeast(1)
val loopStart = inst.sampleLoopStart.toDouble()
val loopEnd = inst.sampleLoopEnd.toDouble().coerceAtLeast(1.0)
val binMax = (SAMPLE_BIN_TOTAL - 1).toInt() // 8 MB pool, addressed via samplePtr directly (not banked)
val i0 = voice.samplePos.toInt().coerceIn(0, sampleLen - 1)
val i1 = (i0 + 1).coerceAtMost(sampleLen - 1)
val frac = voice.samplePos - i0.toDouble()
var b0 = sampleBin[(basePtr + i0).coerceAtMost(binMax).toLong()].toUint()
var b1 = sampleBin[(basePtr + i1).coerceAtMost(binMax).toLong()].toUint()
// S$Fx funk repeat: bit-invert (XOR 0xFF) bytes whose loop-relative index
// is set in funkMask. Mirrors PT2's `*p = -1 - *p` (full bitwise NOT) — the
// mask is a non-destructive overlay so the source sample stays pristine.
// Only meaningful when the sample has a loop region.
if (inst.funkMask != null && inst.sampleLoopEnd > inst.sampleLoopStart) {
val ls = inst.sampleLoopStart
if (i0 in ls until inst.sampleLoopEnd && inst.funkBit(i0 - ls)) b0 = b0 xor 0xFF
if (i1 in ls until inst.sampleLoopEnd && inst.funkBit(i1 - ls)) b1 = b1 xor 0xFF
// Interpolation:
// INTERP_DEFAULT (0): 16-tap windowed sinc (Fast Sinc; MilkyTracker MIXER_SINCTABLE)
// INTERP_NONE (1): nearest-neighbour
// INTERP_A500/A1200 (2/3): zero-order hold per Paula; LPF applied at mix stage
// Edge clamping: out-of-range taps are clipped to sample bounds (acceptable smear
// at sample edges; matches MilkyTracker's outSideLoop fallback).
val sample: Double = when (interpMode) {
INTERP_DEFAULT -> {
var acc = 0.0
// Taps span [i0 - WIDTH + 1, i0 + WIDTH], with the kernel centred on i0+frac.
for (j in -SINC_WIDTH + 1 .. SINC_WIDTH) {
val coeff = sincTap(frac, j)
if (coeff != 0.0) acc += readSamplePoint(inst, i0 + j, sampleLen, binMax) * coeff
}
acc
}
INTERP_NONE, INTERP_A500, INTERP_A1200 ->
// Paula-style ZOH — emit the integer-indexed sample byte without
// sub-sample fade. Aliasing is removed by the post-mix Amiga LPFs.
readSamplePoint(inst, i0, sampleLen, binMax)
else -> readSamplePoint(inst, i0, sampleLen, binMax)
}
val s0 = (b0 - 127.5) / 127.5
val s1 = (b1 - 127.5) / 127.5
val sample = s0 + (s1 - s0) * frac
// While ramping out at sample end, hold position so the mixer keeps emitting the
// clamped last-sample value with decaying gain — no further advance, no re-trigger
@@ -2131,9 +2218,11 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
// 1 $xx00 — Global behaviour flags byte in the high byte (see TAUD_NOTE_EFFECTS.md §1).
// bits 0-1 (ff): 0=linear pitch, 1=Amiga period, 2=linear frequency (Hz/tick),
// 3=reserved
// bits 2-3 (rr): 0=Fast Sinc, 1=none, 2=Amiga 500, 3=Amiga 1200
// Panning law is fixed to the equal-energy; no runtime selection.
val flags = rawArg ushr 8
ts.toneMode = flags and 3
ts.interpolationMode = (flags ushr 2) and 3
}
EffectOp.OP_8 -> {
// 8 $xyzz — Bitcrusher. See TAUD_NOTE_EFFECTS.md §8.
@@ -2421,6 +2510,15 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
val sub = (arg ushr 12) and 0xF
val x = (arg ushr 8) and 0xF
when (sub) {
0x0 -> {
// S $0000 = LED on, S $0100 = LED off (PT E00 / E01 — pt2_replayer.c:608
// computes filterOn = (cmd & 1) ^ 1, so x=0 → on, x=1 → off).
// Only meaningful in Amiga interpolation modes; on linear / no-interp the
// filter chain is bypassed so writes are silent no-ops.
if (ts.interpolationMode == INTERP_A500 || ts.interpolationMode == INTERP_A1200) {
ts.ledFilterOn = (x == 0)
}
}
0x1 -> voice.glissandoOn = (x != 0)
0x2 -> {
voice.noteVal = (voice.noteVal + FINETUNE_OFFSET[x]).coerceIn(1, 0xFFFD)
@@ -2832,7 +2930,7 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
for (voice in ts.voices) {
if (!voice.active || voice.muted) continue
val voiceInst = instruments[voice.instrumentId]
val s = applyTaudVoiceFx(voice, applyVoiceFilter(voice, fetchTrackerSample(voice, voiceInst)))
val s = applyTaudVoiceFx(voice, applyVoiceFilter(voice, fetchTrackerSample(voice, voiceInst, ts.interpolationMode)))
val instGv = voiceInst.instGlobalVolume / 255.0
// Volume swing bias (random per-trigger, ±randomVolBias of 0..255 units folded into the 0..63 row volume).
val swingScale = 1.0 + voice.randomVolBias / 255.0
@@ -2863,7 +2961,7 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
for (bg in ts.backgroundVoices) {
if (!bg.active || bg.muted) continue
val bgInst = instruments[bg.instrumentId]
val s = applyTaudVoiceFx(bg, applyVoiceFilter(bg, fetchTrackerSample(bg, bgInst)))
val s = applyTaudVoiceFx(bg, applyVoiceFilter(bg, fetchTrackerSample(bg, bgInst, ts.interpolationMode)))
val instGv = bgInst.instGlobalVolume / 255.0
val swingScale = 1.0 + bg.randomVolBias / 255.0
val effEnvVol = if (bg.volEnvOn) bg.envVolume else 1.0
@@ -2886,6 +2984,40 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
mixR += s * vol * rGain * rampGain
}
// Amiga interpolation modes: post-mix LPF chain (matches pt2-clone Paula stage).
// INTERP_A500 applies the 1-pole RC LPF (~4421 Hz). INTERP_A1200 has a cutoff
// above Nyquist so its LPF is bypassed. The 2-pole "LED" filter (~3091 Hz, Q≈0.66)
// is added on either Amiga mode when ts.ledFilterOn (S $0000 = on, S $0100 = off).
// No-op for INTERP_DEFAULT and INTERP_NONE so non-Amiga modes pay no cost.
when (ts.interpolationMode) {
INTERP_A500 -> {
ts.amigaLPStateL = mixL * AMIGA_A500_A0 + ts.amigaLPStateL * AMIGA_A500_B1
ts.amigaLPStateR = mixR * AMIGA_A500_A0 + ts.amigaLPStateR * AMIGA_A500_B1
mixL = ts.amigaLPStateL
mixR = ts.amigaLPStateR
if (ts.ledFilterOn) {
val sl = ts.amigaLEDStateL; val sr = ts.amigaLEDStateR
val outL = mixL * AMIGA_LED_A1 + sl[0] * AMIGA_LED_A2 + sl[1] * AMIGA_LED_A1 - sl[2] * AMIGA_LED_B1 - sl[3] * AMIGA_LED_B2
val outR = mixR * AMIGA_LED_A1 + sr[0] * AMIGA_LED_A2 + sr[1] * AMIGA_LED_A1 - sr[2] * AMIGA_LED_B1 - sr[3] * AMIGA_LED_B2
sl[1] = sl[0]; sl[0] = mixL; sl[3] = sl[2]; sl[2] = outL
sr[1] = sr[0]; sr[0] = mixR; sr[3] = sr[2]; sr[2] = outR
mixL = outL; mixR = outR
}
}
INTERP_A1200 -> {
// A1200 1-pole LPF cutoff (~34 kHz) is above Nyquist at SAMPLING_RATE = 32 kHz,
// so it is bypassed (matches pt2_paula.c: useLowpassFilter = false).
if (ts.ledFilterOn) {
val sl = ts.amigaLEDStateL; val sr = ts.amigaLEDStateR
val outL = mixL * AMIGA_LED_A1 + sl[0] * AMIGA_LED_A2 + sl[1] * AMIGA_LED_A1 - sl[2] * AMIGA_LED_B1 - sl[3] * AMIGA_LED_B2
val outR = mixR * AMIGA_LED_A1 + sr[0] * AMIGA_LED_A2 + sr[1] * AMIGA_LED_A1 - sr[2] * AMIGA_LED_B1 - sr[3] * AMIGA_LED_B2
sl[1] = sl[0]; sl[0] = mixL; sl[3] = sl[2]; sl[2] = outL
sr[1] = sr[0]; sr[0] = mixR; sr[3] = sr[2]; sr[2] = outR
mixL = outL; mixR = outR
}
}
}
ts.mixLeft[n] = mixL.toFloat().coerceIn(-1.0f, 1.0f)
ts.mixRight[n] = mixR.toFloat().coerceIn(-1.0f, 1.0f)
}
@@ -3272,6 +3404,21 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
// 3 = reserved
var toneMode = 0
// Interpolation mode (TAUD_NOTE_EFFECTS.md §1, bits 2-3 of global behaviour flags).
// 0=Fast Sinc default, 1=none, 2=Amiga 500, 3=Amiga 1200. See AudioAdapter.INTERP_*.
var interpolationMode = INTERP_DEFAULT
// Amiga "LED" 2-pole LPF on/off (S $0000 = on, S $0100 = off; PT E00/E01).
// Only applies when interpolationMode is INTERP_A500 or INTERP_A1200.
var ledFilterOn = false
// Per-playhead Amiga filter state. Live on the post-mix stereo bus so voice
// come/go does not reset filter history. All zeroed on resetParams().
var amigaLPStateL = 0.0
var amigaLPStateR = 0.0
// 2-pole biquad delay line: [in_z1, in_z2, out_z1, out_z2] for L and R.
val amigaLEDStateL = DoubleArray(4)
val amigaLEDStateR = DoubleArray(4)
// Pending row-end events (set during a row by B/C; consumed at row end).
var pendingOrderJump = -1 // -1 = none; otherwise the order index to jump to
var pendingRowJump = -1 // -1 = none; otherwise the row index for the next pattern
@@ -3383,6 +3530,7 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
initialGlobalFlags = byte
trackerState?.let { ts ->
ts.toneMode = byte and 3
ts.interpolationMode = (byte ushr 2) and 3
}
}
8 -> { bpm = byte + 25 }
@@ -3417,6 +3565,10 @@ class AudioAdapter(val vm: VM) : PeriBase(VM.PERITYPE_SOUND) {
ts.sexWinningChannel = -1
ts.finePatternDelayExtra = 0
ts.toneMode = initialGlobalFlags and 3
ts.interpolationMode = (initialGlobalFlags ushr 2) and 3
ts.ledFilterOn = false
ts.amigaLPStateL = 0.0; ts.amigaLPStateR = 0.0
ts.amigaLEDStateL.fill(0.0); ts.amigaLEDStateR.fill(0.0)
ts.voices.forEach {
it.active = false
it.channelVolume = 0x3F