feat(realtime): Initial Realtime API implementation

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

pkg/sound/int16.go

@@ -0,0 +1,78 @@
+package sound
+
+import "math"
+
+/*
+
+MIT License
+
+Copyright (c) 2024 Xbozon
+
+*/
+
+// calculateRMS16 calculates the root mean square of the audio buffer for int16 samples.
+func CalculateRMS16(buffer []int16) float64 {
+	var sumSquares float64
+	for _, sample := range buffer {
+		val := float64(sample) // Convert int16 to float64 for calculation
+		sumSquares += val * val
+	}
+	meanSquares := sumSquares / float64(len(buffer))
+	return math.Sqrt(meanSquares)
+}
+
+func ResampleInt16(input []int16, inputRate, outputRate int) []int16 {
+	// Calculate the resampling ratio
+	ratio := float64(inputRate) / float64(outputRate)
+
+	// Calculate the length of the resampled output
+	outputLength := int(float64(len(input)) / ratio)
+
+	// Allocate a slice for the resampled output
+	output := make([]int16, outputLength)
+
+	// Perform linear interpolation for resampling
+	for i := 0; i < outputLength-1; i++ {
+		// Calculate the corresponding position in the input
+		pos := float64(i) * ratio
+
+		// Calculate the indices of the surrounding input samples
+		indexBefore := int(pos)
+		indexAfter := indexBefore + 1
+		if indexAfter >= len(input) {
+			indexAfter = len(input) - 1
+		}
+
+		// Calculate the fractional part of the position
+		frac := pos - float64(indexBefore)
+
+		// Linearly interpolate between the two surrounding input samples
+		output[i] = int16((1-frac)*float64(input[indexBefore]) + frac*float64(input[indexAfter]))
+	}
+
+	// Handle the last sample explicitly to avoid index out of range
+	output[outputLength-1] = input[len(input)-1]
+
+	return output
+}
+
+func ConvertInt16ToInt(input []int16) []int {
+	output := make([]int, len(input)) // Allocate a slice for the output
+	for i, value := range input {
+		output[i] = int(value) // Convert each int16 to int and assign it to the output slice
+	}
+	return output // Return the converted slice
+}
+
+func BytesToInt16sLE(bytes []byte) []int16 {
+	// Ensure the byte slice length is even
+	if len(bytes)%2 != 0 {
+		panic("bytesToInt16sLE: input bytes slice has odd length, must be even")
+	}
+
+	int16s := make([]int16, len(bytes)/2)
+	for i := 0; i < len(int16s); i++ {
+		int16s[i] = int16(bytes[2*i]) | int16(bytes[2*i+1])<<8
+	}
+	return int16s
+}