`<MasterMeter>`

(no submodules)

Purpose

<MasterMeter> is a RAF-sampled master-output level meter. It subscribes to a named sidechain bus through the foundation useBus hook ("master" by default) and continuously reads the bus's block-aligned PCM into a scratch buffer at the configured interval, deriving per-channel peak and RMS levels in dB and a slow-decaying peak-hold envelope. When no publisher exists for the bus, every channel shows silence (-∞ dB) so consumers always see something.

The meter is intentionally side-effect-free with respect to the audio graph: it only reads. Nothing inside <MasterMeter> ever writes to the bus or mutates engine state, which keeps it safe to drop into any layout that already has a publisher upstream.

Features

Subscribes to any named bus via useBus(busName).
Per-channel peak + RMS in dB, plus a peak-hold envelope.
Configurable channel count, sample-tick rate, and hold time.
Reads up to Math.min(meterChannels, busChannels) per tick so publisher-wider and meter-wider mismatches do not blow up.
role="meter" + aria-label for screen readers.
data-bus and data-channel attributes for theming hooks.

Usage: Basic Example

import { AudioProvider, MasterMeter } from "@suaveplan/react-audio";

export function App() {
    return (
        <AudioProvider>
            <MasterMeter />
        </AudioProvider>
    );
}

Usage: Advanced Example

import { AudioProvider, MasterMeter } from "@suaveplan/react-audio";

export function AuxMeter() {
    return (
        <AudioProvider>
            <MasterMeter
                busName="auxA"
                channels={1}
                sampleRateHz={120}
                peakHoldMs={2000}
                className="aux-meter"
            />
        </AudioProvider>
    );
}

API Reference

Prop	Type	Default	Notes
`className`	`string \| undef`	—	Forwarded to the outer `<div>`.
`busName`	`string \| undef`	`"master"`	Name of the bus to subscribe to.
`channels`	`number \| undef`	`2`	Number of channel rows to render.
`sampleRateHz`	`number \| undef`	`60`	UI sample tick rate. Clamped to `>= 1`.
`peakHoldMs`	`number \| undef`	`1000`	Peak-hold decay time in milliseconds.

Implementation Notes

The component allocates one persistent scratch Float32Array[] per mount sized to channelCount × 128 so the per-tick read does not allocate. Bus channel mismatches are handled by reading only the narrower side: if the publisher is wider than the meter, only the leading channels are read; if the meter is wider than the publisher, the trailing channels keep their zero-fill from the scratch buffer's last write (which corresponds to silence on next dB conversion). The peak-hold envelope uses one mutable record per channel keeping the current hold value and its expiry timestamp; the value is replaced either when a louder peak arrives or when the hold window expires, which gives the visually slow decay typical of professional meters.

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<MasterMeter>