Add support resampling for PCM for WebRTC

2023-04-22 08:54:31 +03:00
parent fb1cc7dfc2
commit dd98edc48e
3 changed files with 178 additions and 4 deletions
@@ -0,0 +1,116 @@
+package pcm
+
+import (
+	"github.com/AlexxIT/go2rtc/pkg/core"
+	"github.com/pion/rtp"
+)
+
+func Resample(codec *core.Codec, sampleRate uint32, handler core.HandlerFunc) core.HandlerFunc {
+	n := float32(codec.ClockRate) / float32(sampleRate)
+
+	switch codec.Name {
+	case core.CodecPCMA:
+		return DownsampleByte(PCMAtoPCM, PCMtoPCMA, n, handler)
+	case core.CodecPCMU:
+		return DownsampleByte(PCMUtoPCM, PCMtoPCMU, n, handler)
+	case core.CodecPCM:
+		if n == 1 {
+			return ResamplePCM(PCMtoPCMA, handler)
+		}
+		return DownsamplePCM(PCMtoPCMA, n, handler)
+	}
+
+	panic(core.Caller())
+}
+
+func DownsampleByte(
+	toPCM func(byte) int16, fromPCM func(int16) byte, n float32, handler core.HandlerFunc,
+) core.HandlerFunc {
+	var sampleN, sampleSum float32
+	var ts uint32
+
+	return func(packet *rtp.Packet) {
+		samples := len(packet.Payload)
+		newLen := uint32((float32(samples) + sampleN) / n)
+
+		oldSamples := packet.Payload
+		newSamples := make([]byte, newLen)
+
+		var i int
+		for _, sample := range oldSamples {
+			sampleSum += float32(toPCM(sample))
+			if sampleN++; sampleN >= n {
+				newSamples[i] = fromPCM(int16(sampleSum / n))
+				i++
+
+				sampleSum = 0
+				sampleN -= n
+			}
+		}
+
+		ts += newLen
+
+		clone := *packet
+		clone.Payload = newSamples
+		clone.Timestamp = ts
+		handler(&clone)
+	}
+}
+
+func ResamplePCM(fromPCM func(int16) byte, handler core.HandlerFunc) core.HandlerFunc {
+	var ts uint32
+
+	return func(packet *rtp.Packet) {
+		len1 := len(packet.Payload)
+		len2 := len1 / 2
+
+		oldSamples := packet.Payload
+		newSamples := make([]byte, len2)
+
+		var i2 int
+		for i1 := 0; i1 < len1; i1 += 2 {
+			sample := int16(uint16(oldSamples[i1])<<8 | uint16(oldSamples[i1+1]))
+			newSamples[i2] = fromPCM(sample)
+			i2++
+		}
+
+		ts += uint32(len2)
+
+		clone := *packet
+		clone.Payload = newSamples
+		clone.Timestamp = ts
+		handler(&clone)
+	}
+}
+
+func DownsamplePCM(fromPCM func(int16) byte, n float32, handler core.HandlerFunc) core.HandlerFunc {
+	var sampleN, sampleSum float32
+	var ts uint32
+
+	return func(packet *rtp.Packet) {
+		samples := len(packet.Payload) / 2
+		newLen := uint32((float32(samples) + sampleN) / n)
+
+		oldSamples := packet.Payload
+		newSamples := make([]byte, newLen)
+
+		var i2 int
+		for i1 := 0; i1 < len(packet.Payload); i1 += 2 {
+			sampleSum += float32(int16(uint16(oldSamples[i1])<<8 | uint16(oldSamples[i1+1])))
+			if sampleN++; sampleN >= n {
+				newSamples[i2] = fromPCM(int16(sampleSum / n))
+				i2++
+
+				sampleSum = 0
+				sampleN -= n
+			}
+		}
+
+		ts += newLen
+
+		clone := *packet
+		clone.Payload = newSamples
+		clone.Timestamp = ts
+		handler(&clone)
+	}
+}