romdev-xgm2

Pure-JS VGM → XGM2 music converter for the Sega Genesis / Mega Drive (SGDK's XGM2 driver). A faithful port of SGDK's xgm2tool — no Java, no jar, no native binary. Parse a .vgm (or gzipped .vgz), get the compiled XGM2 blob you .incbin into a ROM and play with XGM2_play().

Why this exists: XGM2_play() needs a compiled XGM2 blob (split FM/PSG streams

• sample table), not raw VGM. SGDK's only official VGM→XGM2 compiler is xgm2tool, a Java tool — heavy to bundle in a WASM-only toolchain. This is that tool, ported to JS, so a music path needs zero external dependencies. (ffmpeg cannot do this — XGM2 is a chiptune register stream, not audio samples.)

Usage

import { readFileSync } from "node:fs";
import { vgmToXgm2C } from "romdev-xgm2";

const vgm = readFileSync("song.vgm");           // or a gzipped .vgz
const { blob, cSource, lenDefine } = vgmToXgm2C(vgm, "bgm_level1");

// blob      -> Uint8Array, the XGM2 data (256-byte aligned in ROM)
// cSource   -> ready-to-#include C: `const u8 bgm_level1[] __attribute__((aligned(256)))` + BGM_LEVEL1_LEN
// then in your game:  XGM2_play(bgm_level1);

Lower-level:

import { vgmToXgm2, emitC } from "romdev-xgm2";
const blob = vgmToXgm2(vgm, { packed: true, system: "ntsc" }); // packed = compiled/.xgc form
const c    = emitC(blob, "bgm_level1");

Options

• packed (default true) — emit the compiled XGM2 blob (Z80-ready, what you embed and play). false emits the uncompiled .xgm form.
• system ('ntsc' | 'pal' | null) — force the VGM timing flag (offset 0x24). null keeps the VGM's own value.

In romdev

romdev-mcp wraps this as encodeAudio({target:'xgm2', vgmPath, name}) — emits the C array directly. See the Genesis MENTAL_MODEL "music how-to".

Provenance

Ported from SGDK's tools/xgm2tool (MIT) at the pinned SGDK commit. The XGM2 binary format is specified in SGDK's bin/xgm2.txt.

License

MIT (matches SGDK).