Add volume filter

audio/filter.go

@@ -88,6 +88,38 @@ func (f RealTimeFilter) Process(source Source) Source {
 	}
 }
 
+type VolumeFilter struct {
+	adjustement float32
+}
+
+func NewVolumeFilter(adjustement float32) VolumeFilter {
+	return VolumeFilter{
+		adjustement: adjustement,
+	}
+}
+
+func (f VolumeFilter) Process(source Source) Source {
+	outBlocks := make(chan []float32)
+	go func() {
+		defer close(outBlocks)
+
+		for block := range source.Blocks {
+			out := make([]float32, len(block))
+			for i := range block {
+				out[i] = block[i] * f.adjustement
+			}
+			outBlocks <- out
+		}
+
+	}()
+
+	return Source{
+		Channels:   source.Channels,
+		SampleRate: source.SampleRate,
+		Blocks:     outBlocks,
+	}
+}
+
 type StereoFilter struct {
 }