Amiga Audio In Exe

Amiga Audio In Exe

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flowchart TD
  data["DATA hunk sequences<br/>0xD22 + title 0x1D79"] --> seq["play_sound_seq 0x6FB8<br/>thunk -$7E42"]
  data --> title["overlay 0x283FC<br/>title theme"]
  seq --> tone["play_tone_env 0x77AA"]
  title --> tone
  tone --> paula["audio.device / Paula"]
  gate{"Sounds -$79B0<br/>Walk Beep -$79AF"} --> seq
  remake["mm2::audio AudioSDL<br/>EXTRACTED/audio/*.wav"] -.plays.-> seq
  remake -.plays.-> title

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ASM-traced + remake-verified. Supersedes 25-mm2-music-format.md, 26-audio-callpaths-title-death-shared.md, and 27-mm2-known-songs-catalog.md (those mistook blits / save-parse for music). Controls menu toggles still in 25-audio-sounds-music.md.

Summary

[TOC]

MM2 Amiga sound is Paula square-ish wavetable synthesis via audio.device. All tone tables and the 10 short song/SFX sequences are embedded in the DATA hunk (near A4). Waveforms are generated at runtime into an allocated 0x400-byte buffer. master.32 is a dead filename-table string — ignore it (PC used master.4/master.16 for gfx).

0x6FB8 is play_sound_seq (audio). Older RE notes that called it a “canned on-screen sequence”, “world/3D refresh”, or “castle bytecode runner” were wrong — same address, wrong semantics. See §Wrong docs below.

Pipeline

1. audio_device_init @ 0x7070 — AllocMem 0x2A8, open Audio zero + audio.device, 4 IO channels
2. wave_synth_init @ 0x766E — AllocMem 0x400 → A4-$EDA; fill + octave downsample (0x75E2/0x760A)
3. play_sound_seq @ 0x6FB8 via thunk JSR -$7E42(A4) — arg = sound id 0..9
4. play_tone_env @ 0x77AA — note + duration → period/wave → BeginIO write

Gating inside play_sound_seq:

Id	Gate
0	Walk Beep flag A4-$79AF bit0
1..9	Sounds flag A4-$79B0 bit0

Embedded tables (DATA hunk, A4 base DATA_LOAD+0x7FFE)

A4	DATA off	Role
-$7326	0xCD8	12 Paula periods (C..B): 428, 404, 381, 360, 339, 320, 302, 285, 269, 254, 240, 226
-$734A	0xCB4	Octave wave offsets into synth buffer
-$7338	0xCC6	Octave wave lengths (256..1)
-$7252	0xDAC	Duration/volume index table
-$7232	0xDCC	10 pointers → sequences at 0xD22.. (SFX, not scene bytecode)
-$72FC	0xD02	Ptrs to Audio one..eight name strings in CODE

Sequence format

At DATA 0xD22+: pairs [note+0x10][dur_index] terminated by 0xFF.

ID	WAV export	Notes (midi-ish)	Callers / use
0	00_walk_beep.wav	30/6	Step/turn: -$7E42(0) — Walk Beep
1	01_ui_chirp.wav	12/4	UI / confirm chirp
2	02_phrase_short.wav	44/3…	Short phrase
3	03_victory.wav	41/2…	Combat victory (0x125FC / remake CombatSession)
4	04_phrase_b.wav	39/2…	Phrase B
5	05_flourish.wav	46/3…	Flourish
6	06_combat_a.wav	44/2…	Combat sting A
7	07_menu.wav	49/10…	Menu / controls (0x141BE)
8	08_combat_b.wav	42/3…	Combat sting B
9	09_alert.wav	55/7, 56/5	Hit / alert; also OP_0D index 0x09 (sets exit bit0 in port)

Event VM: OP_0D @ 0x15EC4 → -$7E42 → this table (ids 0..9). Not graphics.

Startup (overlay)

Overlay CODE1 @ 0x25C74 / 0x25C78:

jsr -$7E3C(A4)   ; audio_device_init
jsr -$7E2A(A4)   ; wave_synth_init

Title / “music”

Title theme lives in the DATA hunk and is played by the overlay, not play_sound_seq.

Item	Value
Player	Overlay 0x283FC, loop 0x2841C
Stream	A4-$6285 → DATA 0x1D79
Duration table	A4-$61BC → DATA 0x1E42 (same shape as SFX table)
Length	cmpi #$C5 at loop top; last pair at $C4/$C5 → 99 notes (… 3a 01, then ff ff)
Output	JSR -$7E24(A4) = play_tone_env

Format matches SFX: [note+0x10][dur_index]…. Export: EXTRACTED/audio/title_theme.wav.

The 10 play_sound_seq ids remain short jingles/SFX (victory, walk beep, etc.).

Prior docs mistook bitplane blits (-$7B9C → 0x22EAA, “song” 0x12D) for music.

Timing

All note length comes from play_tone_env @ 0x77AA:

; each duration unit:
pea.l   #1
jsr     -$7B42(A4)   ; → 0x25470 → dos.library Delay (LVO -198)
subq.w  #1, duration
; volume envelope step, then loop while duration > 0

• Delay(1) = one AmigaDOS tick = 1/50 s (dos.library; not display rate).
• Duration word = lookup from title table A4-$61BC / SFX A4-$7252: [64,32,16,8,4,2,1,0, 64,48,24,12,6,3,1,0]
• Title stream: 99 notes / 1024 ticks ≈ 20.5 s at Delay@50Hz (final pair 3a 01 = 32 ticks; most others index 3 → 8 ticks).
• No extra WaitTOF / VBlank wait on this path; title loop helper 0x281B2 is input abort, not tempo.
• Audio IO is BeginIO (-$7B30); it does not add the note length.

Exporter: --tempo-scale 1 = Delay@50Hz. Default 1.2 (60/50) — face-value 50Hz sounded rushed, 2.0 a bit slow.

Remake (game/ → mm2::audio)

Piece	Path
API	game/include/mm2/platform/Audio.h
Desktop	game/src/platform/sdl/AudioSDL.cpp — SDL mixer, 22050 Hz mono S16
Amiga / tests	game/src/platform/AudioStub.cpp — no-op (Paula TBD)
Assets	EXTRACTED/audio/*.wav (copied beside binary or found via data_dir)

init(data_dir)          load 00..09 + title_theme.wav
playSoundSeq(id, sounds, walk)   // mirrors 0x6FB8 gates
playTitleTheme(loop)    // overlay title stream
stopTitleTheme / stopAll

Call sites in the remake:

Seq	C++
0	Movement.cpp (step)
3	CombatSession victory
6 / 8 / 9	combat hit / alert paths
OP_0D	EventVmHelpers::eventVmExecEngineCall → playSoundSeq

Extract / listen

python tools\export_mm2_amiga_sfx.py
# raw ASM pitch:     python tools\export_mm2_amiga_sfx.py --octave-shift 0
# Delay@50Hz tempo:  python tools\export_mm2_amiga_sfx.py --tempo-scale 1
# half-speed:        python tools\export_mm2_amiga_sfx.py --tempo-scale 2

Writes to EXTRACTED/audio/ (see that folder’s README.md for note dumps). Also exports medleys: medley_jingles.wav, medley_title_and_jingles.wav, etc.

Thunk map (A4 = DATA_LOAD + $7FFE)

Thunk	Target
-$7E42	play_sound_seq 0x6FB8
-$7E3C	audio_device_init 0x7070
-$7E30	stop channels 0x7562
-$7E2A	wave_synth_init 0x766E
-$7E24	play_tone_env 0x77AA

Wrong docs / symbols to retire

Claim	Truth
0x6FB8 = on-screen / 3D refresh / castle bytecode	play_sound_seq (audio)
A4-$7232 = scene bytecode ptrs	10 SFX sequence pointers
0x77AA = frame/scene dispatch	play_tone_env
0x823C = audio_init	global save parse
A4-$79B2 = Sounds	panel mode; Sounds is -$79B0
-$7B9C / 0x12D = title song	graphics blit coords
A4-$48C = Paula	graphics.library
master.32 music blob	dead string; ignore
Bootstrap play_song_scripted as music	often text+wait; not the title theme

See also

• 25-audio-sounds-music.md — Controls menu Sounds / Walk Beep
• 07-event-script-opcodes.md — OP_0D
• 43-exploration-input-and-ingame-options.md — step calls -$7E42(0)
• game/README.md — remake audio phase

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See also

Page	Why
Audio Sounds Music	Controls menu toggles
Event Script Opcodes	OP_0D → play_sound_seq
Game Remake	mm2::audio / AudioSDL
RE Tools	export_mm2_amiga_sfx.py