Accuracy in LUFS/VU, configureable VU target

src/types/settings.ts

@@ -1,6 +1,6 @@
 import type { VectorscopeMode } from '../renderer/visualizers/Vectorscope'
 import type { SpectrogramClarityMode, SpectrogramScaleMode } from './spectrogram'
-import type { VUMeterMode, VUMeterNeedleChannels, VUMeterOrientation } from './vumeter'
+import { DEFAULT_VU_REFERENCE_DBFS, type VUMeterMode, type VUMeterNeedleChannels, type VUMeterOrientation } from './vumeter'
 import { DEFAULT_LUFS_METER_READOUT, type LUFSMeterMode, type LUFSMeterReadout } from './lufsmeter'
 import { DEFAULT_WAVEFORM_MODE, type WaveformMode } from './waveform'
 import { DEFAULT_SPECTRUM_PEAK_INFO_MODE, type SpectrumPeakInfoMode } from './spectrum'
@@ -42,6 +42,7 @@ export interface ScopeSettings {
     mode: VUMeterMode
     orientation: VUMeterOrientation
     needleChannels: VUMeterNeedleChannels
+    referenceDb: number
   }
   lufsmeter: {
     mode: LUFSMeterMode
@@ -67,7 +68,7 @@ export const DEFAULT_SCOPE_SETTINGS: ScopeSettings = {
   oscilloscope: { pitchLock: true, underfillEnabled: false, showGrid: true, lineWidth: 2 },
   vectorscope: { mode: 'lissajous', multiband: false, showGrid: true, persistence: 0.10, lineWidth: 1.5 },
   spectrogram: { fftSize: 2048, scrollSpeed: 2, clarityMode: 'sharper', scaleMode: 'log', colorScheme: 'heat' },
-  vumeter: { mode: 'bar', orientation: 'horizontal', needleChannels: 'stereo' },
+  vumeter: { mode: 'bar', orientation: 'horizontal', needleChannels: 'stereo', referenceDb: DEFAULT_VU_REFERENCE_DBFS },
   lufsmeter: { mode: 'bar', readout: DEFAULT_LUFS_METER_READOUT },
   waveform: { mode: DEFAULT_WAVEFORM_MODE, scrollSpeed: 1, multiband: false },
   nowPlaying: {

src/types/vumeter.ts

@@ -10,6 +10,27 @@ export const DEFAULT_VU_METER_MODE: VUMeterMode = 'bar'
 export const DEFAULT_VU_METER_ORIENTATION: VUMeterOrientation = 'horizontal'
 export const DEFAULT_VU_METER_NEEDLE_CHANNELS: VUMeterNeedleChannels = 'stereo'
 
+// Reference-level calibration: 0 VU corresponds to this dBFS value.
+export const DEFAULT_VU_REFERENCE_DBFS = -14
+export const VU_REFERENCE_MIN_DBFS = -30
+export const VU_REFERENCE_MAX_DBFS = 0
+
+export interface VUReferencePreset {
+  readonly id: string
+  readonly label: string
+  readonly description: string
+  readonly dbfs: number
+}
+
+export const VU_REFERENCE_PRESETS: readonly VUReferencePreset[] = [
+  { id: 'k20', label: 'K-20', description: 'SMPTE film', dbfs: -20 },
+  { id: 'k18', label: 'K-18', description: 'EBU broadcast', dbfs: -18 },
+  { id: 'k14', label: 'K-14', description: 'Streaming', dbfs: -14 },
+  { id: 'k12', label: 'K-12', description: 'Modern music', dbfs: -12 },
+  { id: 'k10', label: 'K-10', description: 'Loud masters', dbfs: -10 },
+  { id: 'k6', label: 'K-6', description: 'Hot / legacy', dbfs: -6 },
+]
+
 export function isVUMeterMode(value: unknown): value is VUMeterMode {
   return typeof value === 'string' && VU_METER_MODES.includes(value as VUMeterMode)
 }
@@ -21,3 +42,16 @@ export function isVUMeterOrientation(value: unknown): value is VUMeterOrientatio
 export function isVUMeterNeedleChannels(value: unknown): value is VUMeterNeedleChannels {
   return typeof value === 'string' && VU_METER_NEEDLE_CHANNELS.includes(value as VUMeterNeedleChannels)
 }
+
+export function sanitizeVUReferenceDbfs(value: unknown): number {
+  if (typeof value !== 'number' || !Number.isFinite(value)) {
+    return DEFAULT_VU_REFERENCE_DBFS
+  }
+  if (value < VU_REFERENCE_MIN_DBFS) return VU_REFERENCE_MIN_DBFS
+  if (value > VU_REFERENCE_MAX_DBFS) return VU_REFERENCE_MAX_DBFS
+  return value
+}
+
+export function findVUReferencePreset(dbfs: number): VUReferencePreset | null {
+  return VU_REFERENCE_PRESETS.find((preset) => Math.abs(preset.dbfs - dbfs) < 1e-6) ?? null
+}