Avoid unnecessary byte conversion for PCM.

go.mod

@@ -20,7 +20,6 @@ require (
 	github.com/sirupsen/logrus v1.8.1
 	github.com/stretchr/testify v1.8.4
 	github.com/urfave/cli/v2 v2.25.7
-	github.com/zaf/g711 v0.0.0-20220109202201-cf0017bf0359
 	golang.org/x/exp v0.0.0-20231110203233-9a3e6036ecaa
 	gopkg.in/hraban/opus.v2 v2.0.0-20230925203106-0188a62cb302
 	gopkg.in/yaml.v3 v3.0.1

go.sum

@@ -217,8 +217,6 @@ github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673 h1:bAn7/zixMGCfxrRT
 github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673/go.mod h1:N3UwUGtsrSj3ccvlPHLoLsHnpR27oXr4ZE984MbSER8=
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
-github.com/zaf/g711 v0.0.0-20220109202201-cf0017bf0359 h1:P9yeMx2iNJxJqXEwLtMjSwWcD2a0AlFmFByeosMZhLM=
-github.com/zaf/g711 v0.0.0-20220109202201-cf0017bf0359/go.mod h1:ySLGJD8AQluMQuu5JDvfJrwsBra+8iX1jFsKS8KfB2I=
 github.com/zeebo/assert v1.3.0 h1:g7C04CbJuIDKNPFHmsk4hwZDO5O+kntRxzaUoNXj+IQ=
 github.com/zeebo/assert v1.3.0/go.mod h1:Pq9JiuJQpG8JLJdtkwrJESF0Foym2/D9XMU5ciN/wJ0=
 github.com/zeebo/xxh3 v1.0.2 h1:xZmwmqxHZA8AI603jOQ0tMqmBr9lPeFwGg6d+xy9DC0=

pkg/media/media.go

@@ -14,6 +14,8 @@
 
 package media
 
+import "sync/atomic"
+
 type Writer[T any] interface {
 	WriteSample(sample T) error
 }
@@ -23,3 +25,43 @@ type WriterFunc[T any] func(in T) error
 func (fnc WriterFunc[T]) WriteSample(in T) error {
 	return fnc(in)
 }
+
+type SwitchWriter[T any] struct {
+	ptr atomic.Pointer[Writer[T]]
+}
+
+func (s *SwitchWriter[T]) Get() Writer[T] {
+	ptr := s.ptr.Load()
+	if ptr == nil {
+		return nil
+	}
+	return *ptr
+}
+
+func (s *SwitchWriter[T]) Set(w Writer[T]) {
+	if w == nil {
+		s.ptr.Store(nil)
+	} else {
+		s.ptr.Store(&w)
+	}
+}
+
+func (s *SwitchWriter[T]) WriteSample(sample T) error {
+	w := s.Get()
+	if w == nil {
+		return nil
+	}
+	return w.WriteSample(sample)
+}
+
+type MultiWriter[T any] []Writer[T]
+
+func (s MultiWriter[T]) WriteSample(sample T) error {
+	var last error
+	for _, w := range s {
+		if err := w.WriteSample(sample); err != nil {
+			last = err
+		}
+	}
+	return last
+}

pkg/media/pcm.go

@@ -15,7 +15,6 @@
 package media
 
 import (
-	"encoding/binary"
 	"time"
 
 	"github.com/pion/webrtc/v3/pkg/media"
@@ -37,38 +36,8 @@ func PlayAudio[T any](w Writer[T], sampleDur time.Duration, frames []T) error {
 	return nil
 }
 
-type LPCM16Sample []byte
-
-func (s LPCM16Sample) Decode() PCM16Sample {
-	out := make(PCM16Sample, len(s)/2)
-	for i := 0; i < len(s); i += 2 {
-		out[i/2] = int16(binary.LittleEndian.Uint16(s[i:]))
-	}
-	return out
-}
-
 type PCM16Sample []int16
 
-func (s PCM16Sample) Encode() LPCM16Sample {
-	out := make(LPCM16Sample, len(s)*2)
-	for i, v := range s {
-		binary.LittleEndian.PutUint16(out[2*i:], uint16(v))
-	}
-	return out
-}
-
-func DecodePCM(w Writer[PCM16Sample]) Writer[LPCM16Sample] {
-	return WriterFunc[LPCM16Sample](func(in LPCM16Sample) error {
-		return w.WriteSample(in.Decode())
-	})
-}
-
-func EncodePCM(w Writer[LPCM16Sample]) Writer[PCM16Sample] {
-	return WriterFunc[PCM16Sample](func(in PCM16Sample) error {
-		return w.WriteSample(in.Encode())
-	})
-}
-
 type MediaSampleWriter interface {
 	WriteSample(sample media.Sample) error
 }

pkg/media/ulaw/g711.go

@@ -0,0 +1,155 @@
+/*
+	Copyright (C) 2016 - 2017, Lefteris Zafiris <[email protected]>
+
+	This program is free software, distributed under the terms of
+	the BSD 3-Clause License. See the LICENSE file
+	at the top of the source tree.
+
+	Package g711 implements encoding and decoding of G711 PCM sound data.
+	G.711 is an ITU-T standard for audio companding.
+*/
+
+package ulaw
+
+const (
+	uLawBias = 0x84
+	uLawClip = 0x7F7B
+)
+
+var (
+	// u-law quantization segment lookup table
+	ulawSegment = [256]uint8{
+		0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
+		4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+		5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
+		5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
+		6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+		6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+		6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+		6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+		7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+	}
+	// u-law to LPCM conversion lookup table
+	ulaw2lpcm = [256]int16{
+		-32124, -31100, -30076, -29052, -28028, -27004, -25980, -24956,
+		-23932, -22908, -21884, -20860, -19836, -18812, -17788, -16764,
+		-15996, -15484, -14972, -14460, -13948, -13436, -12924, -12412,
+		-11900, -11388, -10876, -10364, -9852, -9340, -8828, -8316,
+		-7932, -7676, -7420, -7164, -6908, -6652, -6396, -6140,
+		-5884, -5628, -5372, -5116, -4860, -4604, -4348, -4092,
+		-3900, -3772, -3644, -3516, -3388, -3260, -3132, -3004,
+		-2876, -2748, -2620, -2492, -2364, -2236, -2108, -1980,
+		-1884, -1820, -1756, -1692, -1628, -1564, -1500, -1436,
+		-1372, -1308, -1244, -1180, -1116, -1052, -988, -924,
+		-876, -844, -812, -780, -748, -716, -684, -652,
+		-620, -588, -556, -524, -492, -460, -428, -396,
+		-372, -356, -340, -324, -308, -292, -276, -260,
+		-244, -228, -212, -196, -180, -164, -148, -132,
+		-120, -112, -104, -96, -88, -80, -72, -64,
+		-56, -48, -40, -32, -24, -16, -8, 0,
+		32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956,
+		23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764,
+		15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412,
+		11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316,
+		7932, 7676, 7420, 7164, 6908, 6652, 6396, 6140,
+		5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092,
+		3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004,
+		2876, 2748, 2620, 2492, 2364, 2236, 2108, 1980,
+		1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436,
+		1372, 1308, 1244, 1180, 1116, 1052, 988, 924,
+		876, 844, 812, 780, 748, 716, 684, 652,
+		620, 588, 556, 524, 492, 460, 428, 396,
+		372, 356, 340, 324, 308, 292, 276, 260,
+		244, 228, 212, 196, 180, 164, 148, 132,
+		120, 112, 104, 96, 88, 80, 72, 64,
+		56, 48, 40, 32, 24, 16, 8, 0,
+	}
+	// u-law to A-law conversion lookup table based on the ITU-T G.711 specification
+	ulaw2alaw = [256]uint8{
+		42, 43, 40, 41, 46, 47, 44, 45, 34, 35, 32, 33, 38, 39, 36, 37,
+		58, 59, 56, 57, 62, 63, 60, 61, 50, 51, 48, 49, 54, 55, 52, 53,
+		10, 11, 8, 9, 14, 15, 12, 13, 2, 3, 0, 1, 6, 7, 4, 26,
+		27, 24, 25, 30, 31, 28, 29, 18, 19, 16, 17, 22, 23, 20, 21, 106,
+		104, 105, 110, 111, 108, 109, 98, 99, 96, 97, 102, 103, 100, 101, 122, 120,
+		126, 127, 124, 125, 114, 115, 112, 113, 118, 119, 116, 117, 75, 73, 79, 77,
+		66, 67, 64, 65, 70, 71, 68, 69, 90, 91, 88, 89, 94, 95, 92, 93,
+		82, 82, 83, 83, 80, 80, 81, 81, 86, 86, 87, 87, 84, 84, 85, 85,
+		170, 171, 168, 169, 174, 175, 172, 173, 162, 163, 160, 161, 166, 167, 164, 165,
+		186, 187, 184, 185, 190, 191, 188, 189, 178, 179, 176, 177, 182, 183, 180, 181,
+		138, 139, 136, 137, 142, 143, 140, 141, 130, 131, 128, 129, 134, 135, 132, 154,
+		155, 152, 153, 158, 159, 156, 157, 146, 147, 144, 145, 150, 151, 148, 149, 234,
+		232, 233, 238, 239, 236, 237, 226, 227, 224, 225, 230, 231, 228, 229, 250, 248,
+		254, 255, 252, 253, 242, 243, 240, 241, 246, 247, 244, 245, 203, 201, 207, 205,
+		194, 195, 192, 193, 198, 199, 196, 197, 218, 219, 216, 217, 222, 223, 220, 221,
+		210, 210, 211, 211, 208, 208, 209, 209, 214, 214, 215, 215, 212, 212, 213, 213,
+	}
+)
+
+// EncodeUlaw encodes 16bit LPCM data to G711 u-law PCM
+func EncodeUlaw(lpcm []int16) []byte {
+	out := make([]byte, len(lpcm))
+	for i := range lpcm {
+		out[i] = EncodeUlawFrame(lpcm[i])
+	}
+	return out
+}
+
+// EncodeUlawFrame encodes a 16bit LPCM frame to G711 u-law PCM
+func EncodeUlawFrame(frame int16) uint8 {
+	/*
+		The algorithm first stores off the sign. It then adds in a bias value
+		which (due to wrapping) will cause high valued samples to lose precision.
+		The top five most significant bits are pulled out of the sample.
+		Then, the bottom three bits of the compressed byte are generated using the
+		segment look-up table, based on the biased value of the source sample.
+		The 8-bit compressed sample is then finally created by logically OR'ing together
+		the 5 most important bits, the 3 lower bits, and the sign when applicable. The bits
+		are then logically NOT'ed for transmission.
+	*/
+	sign := (frame >> 8) & 0x80
+	if sign != 0 {
+		frame = -frame
+	}
+	if frame > uLawClip {
+		frame = uLawClip
+	}
+	frame += uLawBias
+	segment := ulawSegment[(frame>>7)&0xFF]
+	bottom := (frame >> (segment + 3)) & 0x0F
+	return uint8(^(sign | (int16(segment) << 4) | bottom))
+}
+
+// DecodeUlaw decodes u-law PCM data to 16bit PCM.
+func DecodeUlaw(pcm []byte) []int16 {
+	out := make([]int16, len(pcm))
+	for i := 0; i < len(pcm); i++ {
+		out[i] = ulaw2lpcm[pcm[i]]
+	}
+	return out
+}
+
+// DecodeUlawFrame decodes a u-law PCM frame to 16bit LPCM
+func DecodeUlawFrame(frame uint8) int16 {
+	return ulaw2lpcm[frame]
+}
+
+// Ulaw2Alaw performs direct u-law to A-law data conversion
+func Ulaw2Alaw(ulaw []byte) []byte {
+	alaw := make([]byte, len(ulaw))
+	for i := 0; i < len(alaw); i++ {
+		alaw[i] = ulaw2alaw[ulaw[i]]
+	}
+	return ulaw
+}
+
+// Ulaw2AlawFrame directly converts a u-law frame to A-law
+func Ulaw2AlawFrame(frame uint8) uint8 {
+	return ulaw2alaw[frame]
+}

pkg/media/ulaw/ulaw.go

@@ -15,30 +15,28 @@
 package ulaw
 
 import (
-	"github.com/zaf/g711"
-
 	"github.com/livekit/sip/pkg/media"
 )
 
 type Sample []byte
 
-func (s Sample) Decode() media.LPCM16Sample {
-	return g711.DecodeUlaw(s)
+func (s Sample) Decode() media.PCM16Sample {
+	return DecodeUlaw(s)
 }
 
-func (s *Sample) Encode(data media.LPCM16Sample) {
-	*s = g711.EncodeUlaw(data)
+func (s *Sample) Encode(data media.PCM16Sample) {
+	*s = EncodeUlaw(data)
 }
 
-func Encode(w media.Writer[media.LPCM16Sample]) media.Writer[Sample] {
+func Decode(w media.Writer[media.PCM16Sample]) media.Writer[Sample] {
 	return media.WriterFunc[Sample](func(in Sample) error {
 		out := in.Decode()
 		return w.WriteSample(out)
 	})
 }
 
-func Decode(w media.Writer[Sample]) media.Writer[media.LPCM16Sample] {
-	return media.WriterFunc[media.LPCM16Sample](func(in media.LPCM16Sample) error {
+func Encode(w media.Writer[Sample]) media.Writer[media.PCM16Sample] {
+	return media.WriterFunc[media.PCM16Sample](func(in media.PCM16Sample) error {
 		var s Sample
 		s.Encode(in)
 		return w.WriteSample(s)

pkg/mixer/mixer.go

@@ -43,30 +43,30 @@ type Input struct {
 type Mixer struct {
 	mu sync.Mutex
 
-	onSample func([]byte)
-	inputs   map[*Input]struct{}
+	out    media.Writer[media.PCM16Sample]
+	inputs map[*Input]struct{}
 
 	ticker  *time.Ticker
 	mixSize int
 
 	stopped core.Fuse
 }
 
-func NewMixer(onSample func([]byte), sampleRate int) *Mixer {
-	m := createMixer(onSample, sampleRate)
+func NewMixer(out media.Writer[media.PCM16Sample], sampleRate int) *Mixer {
+	m := createMixer(out, sampleRate)
 
 	go m.start()
 
 	return m
 }
 
-func createMixer(onSample func([]byte), sampleRate int) *Mixer {
+func createMixer(out media.Writer[media.PCM16Sample], sampleRate int) *Mixer {
 	m := &Mixer{
-		onSample: onSample,
-		ticker:   time.NewTicker(mixerTickDuration),
-		mixSize:  int(time.Duration(sampleRate) * mixerTickDuration / time.Second),
-		stopped:  core.NewFuse(),
-		inputs:   make(map[*Input]struct{}),
+		out:     out,
+		ticker:  time.NewTicker(mixerTickDuration),
+		mixSize: int(time.Duration(sampleRate) * mixerTickDuration / time.Second),
+		stopped: core.NewFuse(),
+		inputs:  make(map[*Input]struct{}),
 	}
 
 	return m
@@ -107,21 +107,18 @@ func (m *Mixer) doMix() {
 		input.mu.Unlock()
 	}
 
-	out := make([]byte, 2*m.mixSize)
+	out := make(media.PCM16Sample, m.mixSize)
 	for i, sample := range mixed {
 		if sample > 0x7FFF {
 			sample = 0x7FFF
 		}
 		if sample < -0x7FFF {
 			sample = -0x7FFF
 		}
-
-		// Encoder expects little endian data (???)
-		out[2*i] = byte(sample & 0xFF)
-		out[2*i+1] = byte(sample >> 8)
+		out[i] = int16(sample)
 	}
 
-	m.onSample(out)
+	_ = m.out.WriteSample(out)
 }
 
 func (m *Mixer) start() {