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@spacedevin/deck-player

Web Audio playback for .deck — chip-tune synths, a lookahead transport, and a <deck-player> element.

@spacedevin/deck parses the language and @spacedevin/deck-synths holds the voices. This package is the host: it applies the defaults and clamps the parser deliberately leaves out, sequences the song, and makes sound through the full 33-voice catalog.

Install

npm install @spacedevin/deck-player

@spacedevin/deck and @spacedevin/deck-synths are peer dependencies and install alongside it.

Use

import { createDeckPlayer } from '@spacedevin/deck-player'

const player = createDeckPlayer()
const song = player.load(`
deck 1
bpm 120

track Lead id lead gen gameBoyDmg
  gen type pulse duty 50 vol 12
  note 60 0 0.5 v 100
  note 64 0.5 0.5 v 90
  note 67 1 1 v 100
`)

if (song.errors.length) console.warn(song.errors)
button.onclick = () => player.play()   // an AudioContext needs a user gesture

Or drop in the element — no framework, no build step:

<script type="module" src="/node_modules/@spacedevin/deck-player/element/deck-player-element.js"></script>

<deck-player>
deck 1
bpm 120
track Lead id lead gen gameBoyDmg
  note 60 0 0.5 v 100
</deck-player>

<deck-player src="/music/theme.deck"></deck-player>

Code lighting

If the source inside the element is highlighted HTML rather than plain text, the element will light it as it plays: the step under the playhead in each steps lane, and every line of a track that is sounding on that step. It looks for the attributes the site highlighter emits — data-track on each line and data-step on each step token — so any highlighter that adds those gets the same behaviour. The docs site is the reference: site/highlight.mjs emits them, site/style.css styles the dk-now (lit step) and dk-live (sounding line) classes it toggles.

Hear it

A whole song is three kinds of line: a tempo, a track, and some notes. On the docs site this block has a play button — the synths below are doing the work.

deck 1
bpm 132

track Lead id lead gen gameBoyDmg
  gen type pulse duty 25 vol 11
  note 72 0 0.5 v 110
  note 76 0.5 0.5 v 95
  note 79 1 0.5 v 105
  note 76 1.5 0.5 v 90
  note 72 2 1 v 110
  note 74 3 1 v 95

track Bass id bass gen gameBoyDmg
  gen type wave wave_shape saw vol 15
  note 36 0 1 v 120
  note 36 1 1 v 100
  note 43 2 1 v 115
  note 41 3 1 v 100

track Kick id kick gen gbaDirectSound
  gen waveform triangle pitch_drop -14
  adsr a 0 d 0.08 s 0 r 0
  note 36 0 0.25 v 127
  note 36 1 0.25 v 110
  note 36 2 0.25 v 127
  note 36 3 0.25 v 110

API
createDeckPlayer(opts?) load · play · pause · stop · seek(beat) · position() · duration() · setIntensity(0..3) · analyser() · on(event, fn) · dispose()
renderDeckToBuffer(src, opts?) offline render through the same graph → Promise<AudioBuffer>
parseSong(src) .deck → Song IR. No AudioContext, no sound
stepTriggers(song, step) which notes sound at a 16th step. Pure
buildAudioGraph · createTransport · playStep the pieces, if you want your own loop

load() returns the Song, including three things worth showing a user:

  • errors — parse errors plus host errors (a malformed gen line, a bad wave table)
  • substitutions — generator ids the catalog has no voice for, swapped for basicOsc so the song still plays
  • ignored — language features present in the source that this package doesn't sequence yet: clips/session, song/follow arrangement, auto automation, master_mix, @ directives

Sound

The voices are @spacedevin/deck-synths — all 33 of them, the same catalog Deckard plays through, which is itself checked against tish-gba's build-time bake. So a .deck sounds the same here as it does in Deckard or on a GBA, and nothing is swapped for a stand-in. The chip voices model real hardware behaviour, not an impression of it:

  • gameBoyDmg — the four duty tables in an 8-sample buffer pitched by playbackRate; a genuine 15/7-bit LFSR for noise; wave RAM quantized to 4 bits; the 64 Hz / 32 Hz frequency floors; the 15-step volume envelope
  • gbaDirectSound — a 32-sample table (so high notes alias like the real software mixer), an 8-bit DAC as a 256-step staircase, and the ~16 kHz mixing roll-off
  • nes2a03, c64sid, ym2612, sn76489, spc700 — and the rest of the chip family, plus FM, drums, hard sync, bowed and plucked models. The full list is in the synths README; Examples has a playable song for each
  • wave <name> <32 hex digits> / wave <name> harmonics <a1> … — named wave RAM tables, written as samples or as harmonic amplitudes; the language resolves both to the same 32 levels
  • layer — stem gating via setIntensity()

Two voices reach outside the audio graph: ttsVocal needs the Web Speech API and meSpeakVocal needs a worker the host serves. They play in a page that provides those and are silent in an offline render.

Notes

  • Players are aware of each other. Starting one stops any other that's playing — two chip songs at once is noise, and a page like this one has several players on it. Pass { exclusive: false } to layer them deliberately.
  • One AudioContext per page. Players share a single lazily-created context unless you pass your own, because a context is a page-level resource and Safari has historically refused past about four.
  • No assets to copy. The clock worklet is compiled from an inline string into a Blob URL, so installing the package is the whole install.
  • Deterministic. Probability locks, arpeggiator shuffles and the reverb impulse are all seeded, so two renders of one song are identical.
  • Pause is real pause. It suspends the AudioContext, so notes and the scheduler resume exactly where they stopped.
  • Requires AudioContext; playback must start from a user gesture.

Scope

See AGENTS.md. Grammar changes belong upstream in @spacedevin/deck — never re-tokenize .deck text here.

License

MIT — see LICENSE.