Improved normalizer with running ratio

Kirika_test.go

@@ -86,6 +86,36 @@ func TestVorbisDecode(t *testing.T) {
 	doTest(".vorbis", t)
 }
 
+func TestReplayGainNormalization24(t *testing.T) {
+	t.Parallel()
+
+	fp, err := os.Open(TestSingleSample24)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	defer fp.Close()
+	source, err := flac.NewFormat().Open(fp)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	source = replaygain.NewNormalizationFilter(5).Process(source)
+
+	gain, peak, err := replaygain.GetTrackReplayGain(source)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	expect := "-0.181563 dB, 0.688681"
+	result := fmt.Sprintf("%f dB, %f", gain, peak)
+	if result != expect {
+		t.Errorf("Wrong ReplayGain %s != %s", result, expect)
+	}
+}
+
 func TestReplayGain24(t *testing.T) {
 	t.Parallel()
 

audio/replaygain/filter.go

@@ -70,13 +70,17 @@ func (f NormalizationFilter) Process(source audio.Source) audio.Source {
 			}
 
 			volume := math.Pow(10, (gain)/20)
-			//prevent clipping
-			volume = math.Min(volume, 1/peak)
-
-			adjustment = float32(volume)
 
 			nsamples := source.SampleRate * source.Channels * f.delay
 
+			ratio := float32(math.Min(1, float64(len(block))/float64(nsamples)))
+
+			adjustment = adjustment*(1-ratio) + float32(volume)*ratio
+
+			if adjustment > float32(1/peak) {
+				adjustment = float32(1 / peak)
+			}
+
 			if len(sampleBuffer) > nsamples {
 				size := len(sampleBuffer) - nsamples
 				out := make([]float32, size)