#12 Clipping prevention done outside EBUR128

kartik-venugopal · Aug 21, 2024 · f6cd831 · f6cd831
1 parent 4720d91
commit f6cd831
Show file tree

Hide file tree

Showing 4 changed files with 37 additions and 28 deletions.
diff --git a/....xcodeproj/project.xcworkspace/xcuserdata/kven.xcuserdatad/UserInterfaceState.xcuserstate b/....xcodeproj/project.xcworkspace/xcuserdata/kven.xcuserdatad/UserInterfaceState.xcuserstate
diff --git a/Source/Core/AudioGraph/EffectsUnits/ReplayGain/ReplayGainUnit.swift b/Source/Core/AudioGraph/EffectsUnits/ReplayGain/ReplayGainUnit.swift
@@ -26,6 +26,11 @@ class ReplayGainUnit: EffectsUnit, ReplayGainUnitProtocol {
     var replayGain: ReplayGain? {
 
         didSet {
+
+            if preventClipping {
+                replayGain?.applyClippingPrevention(usingMaxPeakLevel: maxPeakLevel.decibels)
+            }
+
             parmsChanged()
         }
     }
@@ -48,6 +53,11 @@ class ReplayGainUnit: EffectsUnit, ReplayGainUnitProtocol {
     var maxPeakLevel: ReplayGainMaxPeakLevel {
 
         didSet {
+
+            if preventClipping {
+                replayGain?.applyClippingPrevention(usingMaxPeakLevel: maxPeakLevel.decibels)
+            }
+
             parmsChanged()
         }
     }

diff --git a/Source/Core/EBUR128/EBUR128State.swift b/Source/Core/EBUR128/EBUR128State.swift
@@ -81,17 +81,8 @@ class EBUR128State {
         let loudness = try computeLoudness()
         let peak = try computePeak()
         let replayGain = Self.targetLoudness - loudness
-        var replayGainToPreventClipping: Double = replayGain
 
-        let newPeak = pow(10.0, replayGain / 20) * peak
-
-        if newPeak > Self.maxPeak {
-
-            let adjustment = 20 * log10(newPeak / Self.maxPeak)
-            replayGainToPreventClipping -= adjustment
-        }
-
-        return EBUR128AnalysisResult(loudness: loudness, peak: peak, replayGain: replayGain, replayGainToPreventClipping: replayGainToPreventClipping)
+        return EBUR128AnalysisResult(loudness: loudness, peak: peak, replayGain: replayGain)
     }
 
     func computeLoudness() throws -> Double {
@@ -154,7 +145,5 @@ struct EBUR128AnalysisResult {
 
     let loudness: Double
     let peak: Double
-
     let replayGain: Double
-    let replayGainToPreventClipping: Double
 }
diff --git a/Source/Core/TrackIO/Model/ReplayGain.swift b/Source/Core/TrackIO/Model/ReplayGain.swift
@@ -14,39 +14,51 @@ struct ReplayGain {
 
     let trackGain: Float?
     let trackPeak: Float?
-    let trackGainToPreventClipping: Float?
+
+    var trackGainToPreventClipping: Float? = nil
 
     let albumGain: Float?
     let albumPeak: Float?
-    let albumGainToPreventClipping: Float?
 
-    private static let maxPeak: Float = 1
+    var albumGainToPreventClipping: Float? = nil
 
     init?(trackGain: Float? = nil, trackPeak: Float? = nil, albumGain: Float? = nil, albumPeak: Float? = nil) {
 
         guard trackGain != nil || albumGain != nil else {return nil}
 
-        func gainToPreventClipping(gain: Float, peak: Float) -> Float {
-
-            let newPeak = pow(10.0, gain / 20) * peak
-            return newPeak > Self.maxPeak ? gain - (20 * log10(newPeak / Self.maxPeak)) : gain
-        }
-
         self.trackGain = trackGain
         self.trackPeak = trackPeak
 
+        self.albumGain = albumGain
+        self.albumPeak = albumPeak
+    }
+
+    private func gainToPreventClipping(gain: Float, peak: Float, usingMaxPeakLevel maxPeakLevel: Float) -> Float {
+
+        let newPeak = pow(10.0, gain / 20) * peak
+        return newPeak > maxPeakLevel ? gain - (20 * log10(newPeak / maxPeakLevel)) : gain
+    }
+
+    mutating func applyClippingPrevention(usingMaxPeakLevel maxPeakLevel: Float) {
+
+        applyClippingPreventionToTrackGain(usingMaxPeakLevel: maxPeakLevel)
+        applyClippingPreventionToAlbumGain(usingMaxPeakLevel: maxPeakLevel)
+    }
+
+    mutating func applyClippingPreventionToTrackGain(usingMaxPeakLevel maxPeakLevel: Float) {
+
         if let theTrackGain = trackGain, let theTrackPeak = trackPeak {
-            self.trackGainToPreventClipping = gainToPreventClipping(gain: theTrackGain, peak: theTrackPeak)
+            self.trackGainToPreventClipping = gainToPreventClipping(gain: theTrackGain, peak: theTrackPeak, usingMaxPeakLevel: maxPeakLevel)
 
         } else {
             self.trackGainToPreventClipping = nil
         }
-        
-        self.albumGain = albumGain
-        self.albumPeak = albumPeak
+    }
+
+    mutating func applyClippingPreventionToAlbumGain(usingMaxPeakLevel maxPeakLevel: Float) {
 
         if let theAlbumGain = albumGain, let theAlbumPeak = albumPeak {
-            self.albumGainToPreventClipping = gainToPreventClipping(gain: theAlbumGain, peak: theAlbumPeak)
+            self.albumGainToPreventClipping = gainToPreventClipping(gain: theAlbumGain, peak: theAlbumPeak, usingMaxPeakLevel: maxPeakLevel)
         } else {
             self.albumGainToPreventClipping = nil
         }
@@ -56,10 +68,8 @@ struct ReplayGain {
 
         self.trackGain = Float(ebur128AnalysisResult.replayGain)
         self.trackPeak = Float(ebur128AnalysisResult.peak)
-        self.trackGainToPreventClipping = Float(ebur128AnalysisResult.replayGainToPreventClipping)
 
         self.albumGain = nil
         self.albumPeak = nil
-        self.albumGainToPreventClipping = nil
     }
 }