Merge f2bdc8c111fff25f05ecbb0a2a0c4f4ba06e6ebc into a45adbbb2eb5a620173b5c1710017368abfb6be6

ui/src/utils/calculateReplayGain.js

@@ -1,16 +1,25 @@
 const calculateReplayGain = (preAmp, gain, peak) => {
-  if (gain === undefined || peak === undefined) {
+  if (gain == null) {
     return 1
   }
 
   // https://wiki.hydrogenaud.io/index.php?title=ReplayGain_1.0_specification&section=19
   // Normalized to max gain
-  return Math.min(10 ** ((gain + preAmp) / 20), 1 / peak)
+  const replayGain = 10 ** ((gain + preAmp) / 20)
+  return peak == null ? replayGain : Math.min(replayGain, 1 / peak)
 }
 
 export const calculateGain = (gainInfo, song) => {
   switch (gainInfo.gainMode) {
     case 'album': {
+      // Singles and untagged albums have no album gain, so use the track gain.
+      if (song.rgAlbumGain == null) {
+        return calculateReplayGain(
+          gainInfo.preAmp,
+          song.rgTrackGain,
+          song.rgTrackPeak,
+        )
+      }
       return calculateReplayGain(
         gainInfo.preAmp,
         song.rgAlbumGain,

ui/src/utils/calculateReplayGain.test.js

@@ -0,0 +1,90 @@
+import { describe, it, expect } from 'vitest'
+import { calculateGain } from './calculateReplayGain'
+
+describe('calculateGain', () => {
+  const preAmp = 0
+
+  const albumSong = {
+    rgAlbumGain: -6,
+    rgAlbumPeak: 1,
+    rgTrackGain: -3,
+    rgTrackPeak: 1,
+  }
+  const trackOnlySong = {
+    rgTrackGain: -3,
+    rgTrackPeak: 1,
+  }
+  const nativeTrackOnlySong = {
+    rgAlbumGain: null,
+    rgAlbumPeak: null,
+    rgTrackGain: -3,
+    rgTrackPeak: 1,
+  }
+  const noGainSong = {}
+
+  it('uses album gain in album mode when it is present', () => {
+    const result = calculateGain({ gainMode: 'album', preAmp }, albumSong)
+    expect(result).toBeCloseTo(10 ** (-6 / 20))
+  })
+
+  it('falls back to track gain in album mode when the album gain is missing', () => {
+    const result = calculateGain({ gainMode: 'album', preAmp }, trackOnlySong)
+    expect(result).toBeCloseTo(10 ** (-3 / 20))
+  })
+
+  it('falls back to track gain in album mode when the album gain is null', () => {
+    const result = calculateGain(
+      { gainMode: 'album', preAmp },
+      nativeTrackOnlySong,
+    )
+    expect(result).toBeCloseTo(10 ** (-3 / 20))
+  })
+
+  it.each([null, undefined])(
+    'keeps the album gain in album mode when the album peak is %s',
+    (rgAlbumPeak) => {
+      const result = calculateGain(
+        { gainMode: 'album', preAmp },
+        { ...albumSong, rgAlbumPeak },
+      )
+      expect(result).toBeCloseTo(10 ** (-6 / 20))
+    },
+  )
+
+  it('returns 1 in album mode when neither album nor track gain is present', () => {
+    const result = calculateGain({ gainMode: 'album', preAmp }, noGainSong)
+    expect(result).toBe(1)
+  })
+
+  it.each(['album', 'track'])(
+    'does not apply the pre-amp in %s mode to a song without gain tags',
+    (gainMode) => {
+      const result = calculateGain(
+        { gainMode, preAmp: 6 },
+        { ...nativeTrackOnlySong, rgTrackGain: null, rgTrackPeak: null },
+      )
+      expect(result).toBe(1)
+    },
+  )
+
+  it('uses track gain in track mode', () => {
+    const result = calculateGain({ gainMode: 'track', preAmp }, albumSong)
+    expect(result).toBeCloseTo(10 ** (-3 / 20))
+  })
+
+  it.each([null, undefined])(
+    'keeps the track gain in track mode when the track peak is %s',
+    (rgTrackPeak) => {
+      const result = calculateGain(
+        { gainMode: 'track', preAmp },
+        { ...albumSong, rgTrackPeak },
+      )
+      expect(result).toBeCloseTo(10 ** (-3 / 20))
+    },
+  )
+
+  it('returns 1 when gain is disabled', () => {
+    const result = calculateGain({ gainMode: 'none', preAmp }, albumSong)
+    expect(result).toBe(1)
+  })
+})