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game-maker / suite (push) Successful in 12m1s
Sounds follow the road fonts already paved: the file goes to the server content-addressed under its sha256, the project keeps a named asset that points at it, and nothing is ever re-encoded. The format is read from the file's own signature, not from what the browser claims - the same .m4a arrives as audio/mp4, audio/x-m4a or as nothing at all. Playing is two nodes. "Play sound" takes the asset and may raise or lower its volume; every call is its own voice, so two jumps in a row are two jumps heard. Its loop input is a choice of three - from the asset, on, off - because a checkbox has to spend one of its two positions on "not set" and would lose a case: an asset that loops could then never be played once. Below the graph core stays browser-free: NodeContext hands out an asset id, BehaviorSystem resolves it against the project and folds the asset's own volume and loop into the call, and only viewport/SoundLibrary knows about Web Audio. A run without a sink plays nothing instead of throwing. The CI browser is muted, so the ear is no witness: the debug hook counts started and stopped voices, and step 34 reads that counter.
48 lines
1.9 KiB
JavaScript
48 lines
1.9 KiB
JavaScript
/**
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* The seed's sounds, built here instead of shipped or taken from the system: unlike the DejaVu
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* typefaces there is no audio file the host and the CI image are guaranteed to share, and a binary
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* in the repo would be a binary in the repo. WAV is the one format that can be written by hand.
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*
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* The bytes are a pure function of the arguments, so storage stays content-addressed: re-seeding
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* writes the same hash and the checks can name a file by its exact size.
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*/
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const SAMPLE_RATE = 8000;
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const BITS = 16;
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const CHANNELS = 1;
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/**
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* A mono 16-bit PCM sine, faded in and out over a millisecond so it neither clicks on start nor on
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* stop – a decoder is happy either way, but a human listening to the editor's preview is not.
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*/
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export function sineWav(seconds, frequency = 440) {
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const frames = Math.round(SAMPLE_RATE * seconds);
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const data = Buffer.alloc(frames * 2);
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const fade = Math.max(1, Math.round(SAMPLE_RATE * 0.001));
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for (let i = 0; i < frames; i++) {
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const envelope = Math.min(1, i / fade, (frames - 1 - i) / fade);
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const value = Math.sin((2 * Math.PI * frequency * i) / SAMPLE_RATE) * envelope * 0.6;
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data.writeInt16LE(Math.round(value * 32767), i * 2);
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}
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return withRiffHeader(data);
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}
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function withRiffHeader(data) {
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const byteRate = (SAMPLE_RATE * CHANNELS * BITS) / 8;
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const header = Buffer.alloc(44);
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header.write('RIFF', 0);
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header.writeUInt32LE(36 + data.length, 4);
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header.write('WAVE', 8);
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header.write('fmt ', 12);
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header.writeUInt32LE(16, 16); // PCM header length
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header.writeUInt16LE(1, 20); // 1 = uncompressed PCM
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header.writeUInt16LE(CHANNELS, 22);
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header.writeUInt32LE(SAMPLE_RATE, 24);
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header.writeUInt32LE(byteRate, 28);
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header.writeUInt16LE((CHANNELS * BITS) / 8, 32); // block align
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header.writeUInt16LE(BITS, 34);
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header.write('data', 36);
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header.writeUInt32LE(data.length, 40);
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return Buffer.concat([header, data]);
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}
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