useGainNode

The blocks use this hook for every level control and bus: the microphone gain in Mic Setup, the soundboard's master bus, and the output of useSound.

$ pnpm dlx shadcn-svelte@latest add https://juddisjudd.github.io/audiocn-svelte/r/use-gain-node.json

$ npx shadcn-svelte@latest add https://juddisjudd.github.io/audiocn-svelte/r/use-gain-node.json

$ yarn dlx shadcn-svelte@latest add https://juddisjudd.github.io/audiocn-svelte/r/use-gain-node.json

$ bunx --bun shadcn-svelte@latest add https://juddisjudd.github.io/audiocn-svelte/r/use-gain-node.json

Usage

<script lang="ts">
	import { useGainNode } from "#lib/hooks/use-gain-node.svelte.js";
	import { useMicrophone } from "#lib/hooks/use-microphone.svelte.js";
	import { dbToGain } from "#lib/audio/decibels.js";

	let { gainDb }: { gainDb: number } = $props();

	const microphone = useMicrophone({ enabled: true });
	// The microphone, through a gain stage, to the speakers.
	useGainNode(() => ({ gain: dbToGain(gainDb), input: microphone.stream }));
</script>

Call it during component setup. Pass the options as a getter, as above, so the node follows gain, input and destination as they change.

Routing

• input takes a MediaStream, which the hook wraps in a source node, or any AudioNode. Leave it out to feed the node yourself.
• destination is where the node plays. Leave it out for the speakers, pass null to route it yourself, or pass a node such as a mixer input or a MediaStreamAudioDestinationNode.
• The hook returns the node, so you can connect more to it, or pass it to useAudioAnalyser to meter the level after gain. It returns null during server rendering and in browsers without Web Audio. The node stays the same for the life of the component.

Levels

gain is linear: use dbToGain from #lib/audio/decibels.js for decibels. Changes ramp with a short time constant (timeConstant, default 10 ms), so they never click. A new node starts at its gain instead of ramping up from unity, so a muted node is never heard as it starts.

Each connection lives in an effect and is undone on cleanup, so unmounting the component disconnects the node.