New mediadevices design

Changelog:
  * Better support for non-webrtc use cases
  * Enable multiple readers
  * Enhance codec selectors
  * Update APIs to reflect on the new v3 webrtc design
  * Cleaner APIs

codec.go

@@ -0,0 +1,117 @@
+package mediadevices
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/pion/mediadevices/pkg/codec"
+	"github.com/pion/mediadevices/pkg/io/audio"
+	"github.com/pion/mediadevices/pkg/io/video"
+	"github.com/pion/mediadevices/pkg/prop"
+	"github.com/pion/webrtc/v2"
+)
+
+// CodecSelector is a container of video and audio encoder builders, which later will be used
+// for codec matching.
+type CodecSelector struct {
+	videoEncoders []codec.VideoEncoderBuilder
+	audioEncoders []codec.AudioEncoderBuilder
+}
+
+// CodecSelectorOption is a type for specifying CodecSelector options
+type CodecSelectorOption func(*CodecSelector)
+
+// WithVideoEncoders replace current video codecs with listed encoders
+func WithVideoEncoders(encoders ...codec.VideoEncoderBuilder) CodecSelectorOption {
+	return func(t *CodecSelector) {
+		t.videoEncoders = encoders
+	}
+}
+
+// WithVideoEncoders replace current audio codecs with listed encoders
+func WithAudioEncoders(encoders ...codec.AudioEncoderBuilder) CodecSelectorOption {
+	return func(t *CodecSelector) {
+		t.audioEncoders = encoders
+	}
+}
+
+// NewCodecSelector constructs CodecSelector with given variadic options
+func NewCodecSelector(opts ...CodecSelectorOption) *CodecSelector {
+	var track CodecSelector
+
+	for _, opt := range opts {
+		opt(&track)
+	}
+
+	return &track
+}
+
+// Populate lets the webrtc engine be aware of supported codecs that are contained in CodecSelector
+func (selector *CodecSelector) Populate(setting *webrtc.MediaEngine) {
+	for _, encoder := range selector.videoEncoders {
+		setting.RegisterCodec(encoder.RTPCodec().RTPCodec)
+	}
+
+	for _, encoder := range selector.audioEncoders {
+		setting.RegisterCodec(encoder.RTPCodec().RTPCodec)
+	}
+}
+
+func (selector *CodecSelector) selectVideoCodec(wantCodecs []*webrtc.RTPCodec, reader video.Reader, inputProp prop.Media) (codec.ReadCloser, *codec.RTPCodec, error) {
+	var selectedEncoder codec.VideoEncoderBuilder
+	var encodedReader codec.ReadCloser
+	var errReasons []string
+	var err error
+
+outer:
+	for _, wantCodec := range wantCodecs {
+		name := wantCodec.Name
+		for _, encoder := range selector.videoEncoders {
+			if encoder.RTPCodec().Name == name {
+				encodedReader, err = encoder.BuildVideoEncoder(reader, inputProp)
+				if err == nil {
+					selectedEncoder = encoder
+					break outer
+				}
+			}
+
+			errReasons = append(errReasons, fmt.Sprintf("%s: %s", encoder.RTPCodec().Name, err))
+		}
+	}
+
+	if selectedEncoder == nil {
+		return nil, nil, errors.New(strings.Join(errReasons, "\n\n"))
+	}
+
+	return encodedReader, selectedEncoder.RTPCodec(), nil
+}
+
+func (selector *CodecSelector) selectAudioCodec(wantCodecs []*webrtc.RTPCodec, reader audio.Reader, inputProp prop.Media) (codec.ReadCloser, *codec.RTPCodec, error) {
+	var selectedEncoder codec.AudioEncoderBuilder
+	var encodedReader codec.ReadCloser
+	var errReasons []string
+	var err error
+
+outer:
+	for _, wantCodec := range wantCodecs {
+		name := wantCodec.Name
+		for _, encoder := range selector.audioEncoders {
+			if encoder.RTPCodec().Name == name {
+				encodedReader, err = encoder.BuildAudioEncoder(reader, inputProp)
+				if err == nil {
+					selectedEncoder = encoder
+					break outer
+				}
+			}
+
+			errReasons = append(errReasons, fmt.Sprintf("%s: %s", encoder.RTPCodec().Name, err))
+		}
+	}
+
+	if selectedEncoder == nil {
+		return nil, nil, errors.New(strings.Join(errReasons, "\n\n"))
+	}
+
+	return encodedReader, selectedEncoder.RTPCodec(), nil
+}

examples/go.mod

@@ -2,8 +2,11 @@ module github.com/pion/mediadevices/examples
 
 go 1.14
 
+require (
 	// Please don't commit require entries of examples.
 	// `git checkout master examples/go.mod` to revert this file.
-require github.com/pion/mediadevices v0.0.0
+	github.com/pion/mediadevices v0.0.0
+	github.com/pion/webrtc/v2 v2.2.26
+)
 
 replace github.com/pion/mediadevices v0.0.0 => ../

examples/http/main.go

@@ -0,0 +1,77 @@
+// This is an example of using mediadevices to broadcast your camera through http.
+// The example doesn't aim to be performant, but rather it strives to be simple.
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"image/jpeg"
+	"io"
+	"log"
+	"mime/multipart"
+	"net/http"
+	"net/textproto"
+
+	"github.com/pion/mediadevices"
+	"github.com/pion/mediadevices/pkg/prop"
+
+	// Note: If you don't have a camera or microphone or your adapters are not supported,
+	//       you can always swap your adapters with our dummy adapters below.
+	// _ "github.com/pion/mediadevices/pkg/driver/videotest"
+	_ "github.com/pion/mediadevices/pkg/driver/camera" // This is required to register camera adapter
+)
+
+func must(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	s, err := mediadevices.GetUserMedia(mediadevices.MediaStreamConstraints{
+		Video: func(constraint *mediadevices.MediaTrackConstraints) {
+			constraint.Width = prop.Int(600)
+			constraint.Height = prop.Int(400)
+		},
+	})
+	must(err)
+
+	t := s.GetVideoTracks()[0]
+	videoTrack := t.(*mediadevices.VideoTrack)
+
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		var buf bytes.Buffer
+		videoReader := videoTrack.NewReader(false)
+		mimeWriter := multipart.NewWriter(w)
+
+		contentType := fmt.Sprintf("multipart/x-mixed-replace;boundary=%s", mimeWriter.Boundary())
+		w.Header().Add("Content-Type", contentType)
+
+		partHeader := make(textproto.MIMEHeader)
+		partHeader.Add("Content-Type", "image/jpeg")
+
+		for {
+			frame, release, err := videoReader.Read()
+			if err == io.EOF {
+				return
+			}
+			must(err)
+
+			err = jpeg.Encode(&buf, frame, nil)
+			// Since we're done with img, we need to release img so that that the original owner can reuse
+			// this memory.
+			release()
+			must(err)
+
+			partWriter, err := mimeWriter.CreatePart(partHeader)
+			must(err)
+
+			_, err = partWriter.Write(buf.Bytes())
+			buf.Reset()
+			must(err)
+		}
+	})
+
+	fmt.Println("listening on http://localhost:1313")
+	log.Println(http.ListenAndServe("localhost:1313", nil))
+}

examples/webrtc/main.go

@@ -5,26 +5,23 @@ import (
 
 	"github.com/pion/mediadevices"
 	"github.com/pion/mediadevices/examples/internal/signal"
-	"github.com/pion/mediadevices/pkg/codec"
 	"github.com/pion/mediadevices/pkg/frame"
 	"github.com/pion/mediadevices/pkg/prop"
 	"github.com/pion/webrtc/v2"
 
-	// This is required to use opus audio encoder
-	"github.com/pion/mediadevices/pkg/codec/opus"
-
 	// If you don't like vpx, you can also use x264 by importing as below
 	// "github.com/pion/mediadevices/pkg/codec/x264" // This is required to use h264 video encoder
 	// or you can also use openh264 for alternative h264 implementation
 	// "github.com/pion/mediadevices/pkg/codec/openh264"
-	"github.com/pion/mediadevices/pkg/codec/vpx" // This is required to use VP8/VP9 video encoder
+	"github.com/pion/mediadevices/pkg/codec/openh264" // This is required to use VP8/VP9 video encoder
+	"github.com/pion/mediadevices/pkg/codec/opus"     // This is required to use VP8/VP9 video encoder
 
 	// Note: If you don't have a camera or microphone or your adapters are not supported,
 	//       you can always swap your adapters with our dummy adapters below.
 	// _ "github.com/pion/mediadevices/pkg/driver/videotest"
 	// _ "github.com/pion/mediadevices/pkg/driver/audiotest"
+	_ "github.com/pion/mediadevices/pkg/driver/audiotest"
 	_ "github.com/pion/mediadevices/pkg/driver/camera" // This is required to register camera adapter
-	_ "github.com/pion/mediadevices/pkg/driver/microphone" // This is required to register microphone adapter
 )
 
 const (
@@ -61,44 +58,48 @@ func main() {
 		fmt.Printf("Connection State has changed %s \n", connectionState.String())
 	})
 
-	md := mediadevices.NewMediaDevices(peerConnection)
+	vp8Params, err := openh264.NewParams()
+	if err != nil {
+		panic(err)
+	}
+	vp8Params.BitRate = 300_000 // 300kbps
 
 	opusParams, err := opus.NewParams()
 	if err != nil {
 		panic(err)
 	}
-	opusParams.BitRate = 32000 // 32kbps
+	codecSelector := mediadevices.NewCodecSelector(
+		mediadevices.WithVideoEncoders(&vp8Params),
+		mediadevices.WithAudioEncoders(&opusParams),
+	)
 
-	vp8Params, err := vpx.NewVP8Params()
+	s, err := mediadevices.GetUserMedia(mediadevices.MediaStreamConstraints{
-	if err != nil {
-		panic(err)
-	}
-	vp8Params.BitRate = 100000 // 100kbps
-
-	s, err := md.GetUserMedia(mediadevices.MediaStreamConstraints{
-		Audio: func(c *mediadevices.MediaTrackConstraints) {
-			c.Enabled = true
-			c.AudioEncoderBuilders = []codec.AudioEncoderBuilder{&opusParams}
-		},
 		Video: func(c *mediadevices.MediaTrackConstraints) {
 			c.FrameFormat = prop.FrameFormat(frame.FormatYUY2)
-			c.Enabled = true
 			c.Width = prop.Int(640)
 			c.Height = prop.Int(480)
-			c.VideoEncoderBuilders = []codec.VideoEncoderBuilder{&vp8Params}
 		},
+		Audio: func(c *mediadevices.MediaTrackConstraints) {
+		},
+		Codec: codecSelector,
 	})
 	if err != nil {
 		panic(err)
 	}
 
 	for _, tracker := range s.GetTracks() {
-		t := tracker.Track()
 		tracker.OnEnded(func(err error) {
-			fmt.Printf("Track (ID: %s, Label: %s) ended with error: %v\n",
+			fmt.Printf("Track (ID: %s) ended with error: %v\n",
-				t.ID(), t.Label(), err)
+				tracker.ID(), err)
 		})
-		_, err = peerConnection.AddTransceiverFromTrack(t,
+
+		// In Pion/webrtc v3, bind will be called automatically after SDP negotiation
+		webrtcTrack, err := tracker.Bind(peerConnection)
+		if err != nil {
+			panic(err)
+		}
+
+		_, err = peerConnection.AddTransceiverFromTrack(webrtcTrack,
 			webrtc.RtpTransceiverInit{
 				Direction: webrtc.RTPTransceiverDirectionSendonly,
 			},

mediadevices.go

@@ -7,95 +7,26 @@ import (
 
 	"github.com/pion/mediadevices/pkg/driver"
 	"github.com/pion/mediadevices/pkg/prop"
-	"github.com/pion/webrtc/v2"
 )
 
 var errNotFound = fmt.Errorf("failed to find the best driver that fits the constraints")
 
-// MediaDevices is an interface that's defined on https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices
-type MediaDevices interface {
-	GetDisplayMedia(constraints MediaStreamConstraints) (MediaStream, error)
-	GetUserMedia(constraints MediaStreamConstraints) (MediaStream, error)
-	EnumerateDevices() []MediaDeviceInfo
-}
-
-// NewMediaDevices creates MediaDevices interface that provides access to connected media input devices
-// like cameras and microphones, as well as screen sharing.
-// In essence, it lets you obtain access to any hardware source of media data.
-func NewMediaDevices(pc *webrtc.PeerConnection, opts ...MediaDevicesOption) MediaDevices {
-	codecs := make(map[webrtc.RTPCodecType][]*webrtc.RTPCodec)
-	for _, kind := range []webrtc.RTPCodecType{
-		webrtc.RTPCodecTypeAudio,
-		webrtc.RTPCodecTypeVideo,
-	} {
-		codecs[kind] = pc.GetRegisteredRTPCodecs(kind)
-	}
-	return NewMediaDevicesFromCodecs(codecs, opts...)
-}
-
-// NewMediaDevicesFromCodecs creates MediaDevices interface from lists of the available codecs
-// that provides access to connected media input devices like cameras and microphones,
-// as well as screen sharing.
-// In essence, it lets you obtain access to any hardware source of media data.
-func NewMediaDevicesFromCodecs(codecs map[webrtc.RTPCodecType][]*webrtc.RTPCodec, opts ...MediaDevicesOption) MediaDevices {
-	mdo := MediaDevicesOptions{
-		codecs:         codecs,
-		trackGenerator: defaultTrackGenerator,
-	}
-	for _, o := range opts {
-		o(&mdo)
-	}
-	return &mediaDevices{
-		MediaDevicesOptions: mdo,
-	}
-}
-
-// TrackGenerator is a function to create new track.
-type TrackGenerator func(payloadType uint8, ssrc uint32, id, label string, codec *webrtc.RTPCodec) (LocalTrack, error)
-
-var defaultTrackGenerator = TrackGenerator(func(pt uint8, ssrc uint32, id, label string, codec *webrtc.RTPCodec) (LocalTrack, error) {
-	return webrtc.NewTrack(pt, ssrc, id, label, codec)
-})
-
-type mediaDevices struct {
-	MediaDevicesOptions
-}
-
-// MediaDevicesOptions stores parameters used by MediaDevices.
-type MediaDevicesOptions struct {
-	codecs         map[webrtc.RTPCodecType][]*webrtc.RTPCodec
-	trackGenerator TrackGenerator
-}
-
-// MediaDevicesOption is a type of MediaDevices functional option.
-type MediaDevicesOption func(*MediaDevicesOptions)
-
-// WithTrackGenerator specifies a TrackGenerator to use customized track.
-func WithTrackGenerator(gen TrackGenerator) MediaDevicesOption {
-	return func(o *MediaDevicesOptions) {
-		o.trackGenerator = gen
-	}
-}
-
 // GetDisplayMedia prompts the user to select and grant permission to capture the contents
 // of a display or portion thereof (such as a window) as a MediaStream.
 // Reference: https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getDisplayMedia
-func (m *mediaDevices) GetDisplayMedia(constraints MediaStreamConstraints) (MediaStream, error) {
+func GetDisplayMedia(constraints MediaStreamConstraints) (MediaStream, error) {
-	trackers := make([]Tracker, 0)
+	trackers := make([]Track, 0)
 
 	cleanTrackers := func() {
 		for _, t := range trackers {
-			t.Stop()
+			t.Close()
 		}
 	}
 
 	var videoConstraints MediaTrackConstraints
 	if constraints.Video != nil {
 		constraints.Video(&videoConstraints)
-	}
+		tracker, err := selectScreen(videoConstraints, constraints.Codec)
-
-	if videoConstraints.Enabled {
-		tracker, err := m.selectScreen(videoConstraints)
 		if err != nil {
 			cleanTrackers()
 			return nil, err
@@ -116,27 +47,20 @@ func (m *mediaDevices) GetDisplayMedia(constraints MediaStreamConstraints) (Medi
 // GetUserMedia prompts the user for permission to use a media input which produces a MediaStream
 // with tracks containing the requested types of media.
 // Reference: https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia
-func (m *mediaDevices) GetUserMedia(constraints MediaStreamConstraints) (MediaStream, error) {
+func GetUserMedia(constraints MediaStreamConstraints) (MediaStream, error) {
 	// TODO: It should return media stream based on constraints
-	trackers := make([]Tracker, 0)
+	trackers := make([]Track, 0)
 
 	cleanTrackers := func() {
 		for _, t := range trackers {
-			t.Stop()
+			t.Close()
 		}
 	}
 
 	var videoConstraints, audioConstraints MediaTrackConstraints
 	if constraints.Video != nil {
 		constraints.Video(&videoConstraints)
-	}
+		tracker, err := selectVideo(videoConstraints, constraints.Codec)
-
-	if constraints.Audio != nil {
-		constraints.Audio(&audioConstraints)
-	}
-
-	if videoConstraints.Enabled {
-		tracker, err := m.selectVideo(videoConstraints)
 		if err != nil {
 			cleanTrackers()
 			return nil, err
@@ -145,8 +69,9 @@ func (m *mediaDevices) GetUserMedia(constraints MediaStreamConstraints) (MediaSt
 		trackers = append(trackers, tracker)
 	}
 
-	if audioConstraints.Enabled {
+	if constraints.Audio != nil {
-		tracker, err := m.selectAudio(audioConstraints)
+		constraints.Audio(&audioConstraints)
+		tracker, err := selectAudio(audioConstraints, constraints.Codec)
 		if err != nil {
 			cleanTrackers()
 			return nil, err
@@ -240,7 +165,7 @@ func selectBestDriver(filter driver.FilterFn, constraints MediaTrackConstraints)
 	return bestDriver, constraints, nil
 }
 
-func (m *mediaDevices) selectAudio(constraints MediaTrackConstraints) (Tracker, error) {
+func selectAudio(constraints MediaTrackConstraints, selector *CodecSelector) (Track, error) {
 	typeFilter := driver.FilterAudioRecorder()
 
 	d, c, err := selectBestDriver(typeFilter, constraints)
@@ -248,9 +173,9 @@ func (m *mediaDevices) selectAudio(constraints MediaTrackConstraints) (Tracker,
 		return nil, err
 	}
 
-	return newTrack(&m.MediaDevicesOptions, d, c)
+	return newTrackFromDriver(d, c, selector)
 }
-func (m *mediaDevices) selectVideo(constraints MediaTrackConstraints) (Tracker, error) {
+func selectVideo(constraints MediaTrackConstraints, selector *CodecSelector) (Track, error) {
 	typeFilter := driver.FilterVideoRecorder()
 	notScreenFilter := driver.FilterNot(driver.FilterDeviceType(driver.Screen))
 	filter := driver.FilterAnd(typeFilter, notScreenFilter)
@@ -260,10 +185,10 @@ func (m *mediaDevices) selectVideo(constraints MediaTrackConstraints) (Tracker,
 		return nil, err
 	}
 
-	return newTrack(&m.MediaDevicesOptions, d, c)
+	return newTrackFromDriver(d, c, selector)
 }
 
-func (m *mediaDevices) selectScreen(constraints MediaTrackConstraints) (Tracker, error) {
+func selectScreen(constraints MediaTrackConstraints, selector *CodecSelector) (Track, error) {
 	typeFilter := driver.FilterVideoRecorder()
 	screenFilter := driver.FilterDeviceType(driver.Screen)
 	filter := driver.FilterAnd(typeFilter, screenFilter)
@@ -273,10 +198,10 @@ func (m *mediaDevices) selectScreen(constraints MediaTrackConstraints) (Tracker,
 		return nil, err
 	}
 
-	return newTrack(&m.MediaDevicesOptions, d, c)
+	return newTrackFromDriver(d, c, selector)
 }
 
-func (m *mediaDevices) EnumerateDevices() []MediaDeviceInfo {
+func EnumerateDevices() []MediaDeviceInfo {
 	drivers := driver.GetManager().Query(
 		driver.FilterFn(func(driver.Driver) bool { return true }))
 	info := make([]MediaDeviceInfo, 0, len(drivers))

mediadevices_test.go

@@ -1,91 +1,42 @@
 package mediadevices
 
 import (
-	"errors"
 	"io"
 	"testing"
 	"time"
 
-	"github.com/pion/webrtc/v2"
-	"github.com/pion/webrtc/v2/pkg/media"
-
-	"github.com/pion/mediadevices/pkg/codec"
 	"github.com/pion/mediadevices/pkg/driver"
 	_ "github.com/pion/mediadevices/pkg/driver/audiotest"
 	_ "github.com/pion/mediadevices/pkg/driver/videotest"
-	"github.com/pion/mediadevices/pkg/io/audio"
-	"github.com/pion/mediadevices/pkg/io/video"
 	"github.com/pion/mediadevices/pkg/prop"
 )
 
 func TestGetUserMedia(t *testing.T) {
-	videoParams := mockParams{
-		BaseParams: codec.BaseParams{
-			BitRate: 100000,
-		},
-		name: "MockVideo",
-	}
-	audioParams := mockParams{
-		BaseParams: codec.BaseParams{
-			BitRate: 32000,
-		},
-		name: "MockAudio",
-	}
-	md := NewMediaDevicesFromCodecs(
-		map[webrtc.RTPCodecType][]*webrtc.RTPCodec{
-			webrtc.RTPCodecTypeVideo: {
-				{Type: webrtc.RTPCodecTypeVideo, Name: "MockVideo", PayloadType: 1},
-			},
-			webrtc.RTPCodecTypeAudio: {
-				{Type: webrtc.RTPCodecTypeAudio, Name: "MockAudio", PayloadType: 2},
-			},
-		},
-		WithTrackGenerator(
-			func(_ uint8, _ uint32, id, _ string, codec *webrtc.RTPCodec) (
-				LocalTrack, error,
-			) {
-				return newMockTrack(codec, id), nil
-			},
-		),
-	)
 	constraints := MediaStreamConstraints{
 		Video: func(c *MediaTrackConstraints) {
-			c.Enabled = true
 			c.Width = prop.Int(640)
 			c.Height = prop.Int(480)
-			params := videoParams
-			c.VideoEncoderBuilders = []codec.VideoEncoderBuilder{&params}
 		},
 		Audio: func(c *MediaTrackConstraints) {
-			c.Enabled = true
-			params := audioParams
-			c.AudioEncoderBuilders = []codec.AudioEncoderBuilder{&params}
 		},
 	}
 	constraintsWrong := MediaStreamConstraints{
 		Video: func(c *MediaTrackConstraints) {
-			c.Enabled = true
+			c.Width = prop.IntExact(10000)
-			c.Width = prop.Int(640)
 			c.Height = prop.Int(480)
-			params := videoParams
-			params.BitRate = 0
-			c.VideoEncoderBuilders = []codec.VideoEncoderBuilder{&params}
 		},
 		Audio: func(c *MediaTrackConstraints) {
-			c.Enabled = true
-			params := audioParams
-			c.AudioEncoderBuilders = []codec.AudioEncoderBuilder{&params}
 		},
 	}
 
 	// GetUserMedia with broken parameters
-	ms, err := md.GetUserMedia(constraintsWrong)
+	ms, err := GetUserMedia(constraintsWrong)
 	if err == nil {
 		t.Fatal("Expected error, but got nil")
 	}
 
 	// GetUserMedia with correct parameters
-	ms, err = md.GetUserMedia(constraints)
+	ms, err = GetUserMedia(constraints)
 	if err != nil {
 		t.Fatalf("Unexpected error: %v", err)
 	}
@@ -103,11 +54,11 @@ func TestGetUserMedia(t *testing.T) {
 	time.Sleep(50 * time.Millisecond)
 
 	for _, track := range tracks {
-		track.Stop()
+		track.Close()
 	}
 
 	// Stop and retry GetUserMedia
-	ms, err = md.GetUserMedia(constraints)
+	ms, err = GetUserMedia(constraints)
 	if err != nil {
 		t.Fatalf("Failed to GetUserMedia after the previsous tracks stopped: %v", err)
 	}
@@ -124,106 +75,10 @@ func TestGetUserMedia(t *testing.T) {
 	}
 	time.Sleep(50 * time.Millisecond)
 	for _, track := range tracks {
-		track.Stop()
+		track.Close()
 	}
 }
 
-type mockTrack struct {
-	codec *webrtc.RTPCodec
-	id    string
-}
-
-func newMockTrack(codec *webrtc.RTPCodec, id string) *mockTrack {
-	return &mockTrack{
-		codec: codec,
-		id:    id,
-	}
-}
-
-func (t *mockTrack) WriteSample(s media.Sample) error {
-	return nil
-}
-
-func (t *mockTrack) Codec() *webrtc.RTPCodec {
-	return t.codec
-}
-
-func (t *mockTrack) ID() string {
-	return t.id
-}
-
-func (t *mockTrack) Kind() webrtc.RTPCodecType {
-	return t.codec.Type
-}
-
-type mockParams struct {
-	codec.BaseParams
-	name string
-}
-
-func (params *mockParams) RTPCodec() *codec.RTPCodec {
-	rtpCodec := codec.NewRTPH264Codec(90000)
-	rtpCodec.Name = params.name
-	return rtpCodec
-}
-
-func (params *mockParams) BuildVideoEncoder(r video.Reader, p prop.Media) (codec.ReadCloser, error) {
-	if params.BitRate == 0 {
-		// This is a dummy error to test the failure condition.
-		return nil, errors.New("wrong codec parameter")
-	}
-	return &mockVideoCodec{
-		r:      r,
-		closed: make(chan struct{}),
-	}, nil
-}
-
-func (params *mockParams) BuildAudioEncoder(r audio.Reader, p prop.Media) (codec.ReadCloser, error) {
-	return &mockAudioCodec{
-		r:      r,
-		closed: make(chan struct{}),
-	}, nil
-}
-
-type mockCodec struct{}
-
-func (e *mockCodec) SetBitRate(b int) error {
-	return nil
-}
-
-func (e *mockCodec) ForceKeyFrame() error {
-	return nil
-}
-
-type mockVideoCodec struct {
-	mockCodec
-	r      video.Reader
-	closed chan struct{}
-}
-
-func (m *mockVideoCodec) Read() ([]byte, func(), error) {
-	if _, _, err := m.r.Read(); err != nil {
-		return nil, func() {}, err
-	}
-	return make([]byte, 20), func() {}, nil
-}
-
-func (m *mockVideoCodec) Close() error { return nil }
-
-type mockAudioCodec struct {
-	mockCodec
-	r      audio.Reader
-	closed chan struct{}
-}
-
-func (m *mockAudioCodec) Read() ([]byte, func(), error) {
-	if _, _, err := m.r.Read(); err != nil {
-		return nil, func() {}, err
-	}
-	return make([]byte, 20), func() {}, nil
-}
-func (m *mockAudioCodec) Close() error { return nil }
-
 func TestSelectBestDriverConstraintsResultIsSetProperly(t *testing.T) {
 	filterFn := driver.FilterVideoRecorder()
 	drivers := driver.GetManager().Query(filterFn)

mediastream.go

@@ -7,19 +7,19 @@ import (
 // MediaStream is an interface that represents a collection of existing tracks.
 type MediaStream interface {
 	// GetAudioTracks implements https://w3c.github.io/mediacapture-main/#dom-mediastream-getaudiotracks
-	GetAudioTracks() []Tracker
+	GetAudioTracks() []Track
 	// GetVideoTracks implements https://w3c.github.io/mediacapture-main/#dom-mediastream-getvideotracks
-	GetVideoTracks() []Tracker
+	GetVideoTracks() []Track
 	// GetTracks implements https://w3c.github.io/mediacapture-main/#dom-mediastream-gettracks
-	GetTracks() []Tracker
+	GetTracks() []Track
 	// AddTrack implements https://w3c.github.io/mediacapture-main/#dom-mediastream-addtrack
-	AddTrack(t Tracker)
+	AddTrack(t Track)
 	// RemoveTrack implements https://w3c.github.io/mediacapture-main/#dom-mediastream-removetrack
-	RemoveTrack(t Tracker)
+	RemoveTrack(t Track)
 }
 
 type mediaStream struct {
-	trackers map[Tracker]struct{}
+	tracks map[Track]struct{}
 	l      sync.RWMutex
 }
 
@@ -27,60 +27,60 @@ const trackTypeDefault MediaDeviceType = 0
 
 // NewMediaStream creates a MediaStream interface that's defined in
 // https://w3c.github.io/mediacapture-main/#dom-mediastream
-func NewMediaStream(trackers ...Tracker) (MediaStream, error) {
+func NewMediaStream(tracks ...Track) (MediaStream, error) {
-	m := mediaStream{trackers: make(map[Tracker]struct{})}
+	m := mediaStream{tracks: make(map[Track]struct{})}
 
-	for _, tracker := range trackers {
+	for _, track := range tracks {
-		if _, ok := m.trackers[tracker]; !ok {
+		if _, ok := m.tracks[track]; !ok {
-			m.trackers[tracker] = struct{}{}
+			m.tracks[track] = struct{}{}
 		}
 	}
 
 	return &m, nil
 }
 
-func (m *mediaStream) GetAudioTracks() []Tracker {
+func (m *mediaStream) GetAudioTracks() []Track {
 	return m.queryTracks(AudioInput)
 }
 
-func (m *mediaStream) GetVideoTracks() []Tracker {
+func (m *mediaStream) GetVideoTracks() []Track {
 	return m.queryTracks(VideoInput)
 }
 
-func (m *mediaStream) GetTracks() []Tracker {
+func (m *mediaStream) GetTracks() []Track {
 	return m.queryTracks(trackTypeDefault)
 }
 
 // queryTracks returns all tracks that are the same kind as t.
 // If t is 0, which is the default, queryTracks will return all the tracks.
-func (m *mediaStream) queryTracks(t MediaDeviceType) []Tracker {
+func (m *mediaStream) queryTracks(t MediaDeviceType) []Track {
 	m.l.RLock()
 	defer m.l.RUnlock()
 
-	result := make([]Tracker, 0)
+	result := make([]Track, 0)
-	for tracker := range m.trackers {
+	for track := range m.tracks {
-		if tracker.Kind() == t || t == trackTypeDefault {
+		if track.Kind() == t || t == trackTypeDefault {
-			result = append(result, tracker)
+			result = append(result, track)
 		}
 	}
 
 	return result
 }
 
-func (m *mediaStream) AddTrack(t Tracker) {
+func (m *mediaStream) AddTrack(t Track) {
 	m.l.Lock()
 	defer m.l.Unlock()
 
-	if _, ok := m.trackers[t]; ok {
+	if _, ok := m.tracks[t]; ok {
 		return
 	}
 
-	m.trackers[t] = struct{}{}
+	m.tracks[t] = struct{}{}
 }
 
-func (m *mediaStream) RemoveTrack(t Tracker) {
+func (m *mediaStream) RemoveTrack(t Track) {
 	m.l.Lock()
 	defer m.l.Unlock()
 
-	delete(m.trackers, t)
+	delete(m.tracks, t)
 }

mediastream_test.go

@@ -10,17 +10,14 @@ type mockMediaStreamTrack struct {
 	kind MediaDeviceType
 }
 
-func (track *mockMediaStreamTrack) Track() *webrtc.Track {
+func (track *mockMediaStreamTrack) ID() string {
-	return nil
+	return ""
 }
 
-func (track *mockMediaStreamTrack) LocalTrack() LocalTrack {
+func (track *mockMediaStreamTrack) Close() error {
 	return nil
 }
 
-func (track *mockMediaStreamTrack) Stop() {
-}
-
 func (track *mockMediaStreamTrack) Kind() MediaDeviceType {
 	return track.kind
 }
@@ -28,8 +25,16 @@ func (track *mockMediaStreamTrack) Kind() MediaDeviceType {
 func (track *mockMediaStreamTrack) OnEnded(handler func(error)) {
 }
 
+func (track *mockMediaStreamTrack) Bind(pc *webrtc.PeerConnection) (*webrtc.Track, error) {
+	return nil, nil
+}
+
+func (track *mockMediaStreamTrack) Unbind(pc *webrtc.PeerConnection) error {
+	return nil
+}
+
 func TestMediaStreamFilters(t *testing.T) {
-	audioTracks := []Tracker{
+	audioTracks := []Track{
 		&mockMediaStreamTrack{AudioInput},
 		&mockMediaStreamTrack{AudioInput},
 		&mockMediaStreamTrack{AudioInput},
@@ -37,7 +42,7 @@ func TestMediaStreamFilters(t *testing.T) {
 		&mockMediaStreamTrack{AudioInput},
 	}
 
-	videoTracks := []Tracker{
+	videoTracks := []Track{
 		&mockMediaStreamTrack{VideoInput},
 		&mockMediaStreamTrack{VideoInput},
 		&mockMediaStreamTrack{VideoInput},
@@ -49,7 +54,7 @@ func TestMediaStreamFilters(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	expect := func(t *testing.T, actual, expected []Tracker) {
+	expect := func(t *testing.T, actual, expected []Track) {
 		if len(actual) != len(expected) {
 			t.Fatalf("%s: Expected to get %d trackers, but got %d trackers", t.Name(), len(expected), len(actual))
 		}

mediastreamconstraints.go

@@ -1,40 +1,18 @@
 package mediadevices
 
 import (
-	"github.com/pion/mediadevices/pkg/codec"
-	"github.com/pion/mediadevices/pkg/io/audio"
-	"github.com/pion/mediadevices/pkg/io/video"
 	"github.com/pion/mediadevices/pkg/prop"
 )
 
 type MediaStreamConstraints struct {
 	Audio MediaOption
 	Video MediaOption
+	Codec *CodecSelector
 }
 
 // MediaTrackConstraints represents https://w3c.github.io/mediacapture-main/#dom-mediatrackconstraints
 type MediaTrackConstraints struct {
 	prop.MediaConstraints
-	Enabled bool
-	// VideoEncoderBuilders are codec builders that are used for encoding the video
-	// and later being used for sending the appropriate RTP payload type.
-	//
-	// If one encoder builder fails to build the codec, the next builder will be used,
-	// repeating until a codec builds. If no builders build successfully, an error is returned.
-	VideoEncoderBuilders []codec.VideoEncoderBuilder
-	// AudioEncoderBuilders are codec builders that are used for encoding the audio
-	// and later being used for sending the appropriate RTP payload type.
-	//
-	// If one encoder builder fails to build the codec, the next builder will be used,
-	// repeating until a codec builds. If no builders build successfully, an error is returned.
-	AudioEncoderBuilders []codec.AudioEncoderBuilder
-	// VideoTransform will be used to transform the video that's coming from the driver.
-	// So, basically it'll look like following: driver -> VideoTransform -> codec
-	VideoTransform video.TransformFunc
-	// AudioTransform will be used to transform the audio that's coming from the driver.
-	// So, basically it'll look like following: driver -> AudioTransform -> code
-	AudioTransform audio.TransformFunc
-
 	selectedMedia prop.Media
 }
 

sampler.go

@@ -4,6 +4,7 @@ import (
 	"math"
 	"time"
 
+	"github.com/pion/webrtc/v2"
 	"github.com/pion/webrtc/v2/pkg/media"
 )
 
@@ -11,7 +12,7 @@ type samplerFunc func(b []byte) error
 
 // newVideoSampler creates a video sampler that uses the actual video frame rate and
 // the codec's clock rate to come up with a duration for each sample.
-func newVideoSampler(t LocalTrack) samplerFunc {
+func newVideoSampler(t *webrtc.Track) samplerFunc {
 	clockRate := float64(t.Codec().ClockRate)
 	lastTimestamp := time.Now()
 
@@ -27,7 +28,7 @@ func newVideoSampler(t LocalTrack) samplerFunc {
 
 // newAudioSampler creates a audio sampler that uses a fixed latency and
 // the codec's clock rate to come up with a duration for each sample.
-func newAudioSampler(t LocalTrack, latency time.Duration) samplerFunc {
+func newAudioSampler(t *webrtc.Track, latency time.Duration) samplerFunc {
 	samples := uint32(math.Round(float64(t.Codec().ClockRate) * latency.Seconds()))
 	return samplerFunc(func(b []byte) error {
 		return t.WriteSample(media.Sample{Data: b, Samples: samples})

source.go

@@ -0,0 +1 @@
+package mediadevices

track.go

@@ -2,239 +2,326 @@ package mediadevices
 
 import (
 	"errors"
+	"fmt"
+	"image"
 	"math/rand"
 	"sync"
 
 	"github.com/pion/mediadevices/pkg/codec"
 	"github.com/pion/mediadevices/pkg/driver"
+	"github.com/pion/mediadevices/pkg/io/audio"
+	"github.com/pion/mediadevices/pkg/io/video"
+	"github.com/pion/mediadevices/pkg/wave"
 	"github.com/pion/webrtc/v2"
-	"github.com/pion/webrtc/v2/pkg/media"
 )
 
-// Tracker is an interface that represent MediaStreamTrack
+var (
+	errInvalidDriverType      = errors.New("invalid driver type")
+	errNotFoundPeerConnection = errors.New("failed to find given peer connection")
+)
+
+// Source is a generic representation of a media source
+type Source interface {
+	ID() string
+	Close() error
+}
+
+// VideoSource is a specific type of media source that emits a series of video frames
+type VideoSource interface {
+	video.Reader
+	Source
+}
+
+// AudioSource is a specific type of media source that emits a series of audio chunks
+type AudioSource interface {
+	audio.Reader
+	Source
+}
+
+// Track is an interface that represent MediaStreamTrack
 // Reference: https://w3c.github.io/mediacapture-main/#mediastreamtrack
-type Tracker interface {
+type Track interface {
-	Track() *webrtc.Track
+	Source
-	LocalTrack() LocalTrack
-	Stop()
-	Kind() MediaDeviceType
 	// OnEnded registers a handler to receive an error from the media stream track.
 	// If the error is already occured before registering, the handler will be
 	// immediately called.
 	OnEnded(func(error))
+	Kind() MediaDeviceType
+	// Bind binds the current track source to the given peer connection. In Pion/webrtc v3, the bind
+	// call will happen automatically after the SDP negotiation. Users won't need to call this manually.
+	Bind(*webrtc.PeerConnection) (*webrtc.Track, error)
+	// Unbind is the clean up operation that should be called after Bind. Similar to Bind, unbind will
+	// be called automatically in the future.
+	Unbind(*webrtc.PeerConnection) error
 }
 
-type LocalTrack interface {
+type baseTrack struct {
-	WriteSample(s media.Sample) error
+	Source
-	Codec() *webrtc.RTPCodec
-	ID() string
-	Kind() webrtc.RTPCodecType
-}
-
-type track struct {
-	localTrack LocalTrack
-	d          driver.Driver
-	sample     samplerFunc
-	encoder    codec.ReadCloser
-
-	onErrorHandler func(error)
 	err                   error
+	onErrorHandler        func(error)
 	mu                    sync.Mutex
 	endOnce               sync.Once
 	kind                  MediaDeviceType
+	selector              *CodecSelector
+	activePeerConnections map[*webrtc.PeerConnection]chan<- chan<- struct{}
 }
 
-func newTrack(opts *MediaDevicesOptions, d driver.Driver, constraints MediaTrackConstraints) (*track, error) {
+func newBaseTrack(source Source, kind MediaDeviceType, selector *CodecSelector) *baseTrack {
-	var encoderBuilders []encoderBuilder
+	return &baseTrack{
-	var rtpCodecs []*webrtc.RTPCodec
+		Source:                source,
-	var buildSampler func(t LocalTrack) samplerFunc
-	var kind MediaDeviceType
-	var err error
-
-	err = d.Open()
-	if err != nil {
-		return nil, err
-	}
-
-	switch r := d.(type) {
-	case driver.VideoRecorder:
-		kind = VideoInput
-		rtpCodecs = opts.codecs[webrtc.RTPCodecTypeVideo]
-		buildSampler = newVideoSampler
-		encoderBuilders, err = newVideoEncoderBuilders(r, constraints)
-	case driver.AudioRecorder:
-		kind = AudioInput
-		rtpCodecs = opts.codecs[webrtc.RTPCodecTypeAudio]
-		buildSampler = func(t LocalTrack) samplerFunc {
-			return newAudioSampler(t, constraints.selectedMedia.Latency)
-		}
-		encoderBuilders, err = newAudioEncoderBuilders(r, constraints)
-	default:
-		err = errors.New("newTrack: invalid driver type")
-	}
-
-	if err != nil {
-		d.Close()
-		return nil, err
-	}
-
-	for _, builder := range encoderBuilders {
-		var matchedRTPCodec *webrtc.RTPCodec
-		for _, rtpCodec := range rtpCodecs {
-			if rtpCodec.Name == builder.name {
-				matchedRTPCodec = rtpCodec
-				break
-			}
-		}
-
-		if matchedRTPCodec == nil {
-			continue
-		}
-
-		localTrack, err := opts.trackGenerator(
-			matchedRTPCodec.PayloadType,
-			rand.Uint32(),
-			d.ID(),
-			matchedRTPCodec.Type.String(),
-			matchedRTPCodec,
-		)
-		if err != nil {
-			continue
-		}
-
-		encoder, err := builder.build()
-		if err != nil {
-			continue
-		}
-
-		t := track{
-			localTrack: localTrack,
-			sample:     buildSampler(localTrack),
-			d:          d,
-			encoder:    encoder,
 		kind:                  kind,
+		selector:              selector,
+		activePeerConnections: make(map[*webrtc.PeerConnection]chan<- chan<- struct{}),
 	}
-		go t.start()
-		return &t, nil
-	}
-
-	d.Close()
-	return nil, errors.New("newTrack: failed to find a matching codec")
 }
 
 // Kind returns track's kind
-func (t *track) Kind() MediaDeviceType {
+func (track *baseTrack) Kind() MediaDeviceType {
-	return t.kind
+	return track.kind
 }
 
 // OnEnded sets an error handler. When a track has been created and started, if an
 // error occurs, handler will get called with the error given to the parameter.
-func (t *track) OnEnded(handler func(error)) {
+func (track *baseTrack) OnEnded(handler func(error)) {
-	t.mu.Lock()
+	track.mu.Lock()
-	t.onErrorHandler = handler
+	track.onErrorHandler = handler
-	err := t.err
+	err := track.err
-	t.mu.Unlock()
+	track.mu.Unlock()
 
 	if err != nil && handler != nil {
 		// Already errored.
-		t.endOnce.Do(func() {
+		track.endOnce.Do(func() {
 			handler(err)
 		})
 	}
 }
 
 // onError is a callback when an error occurs
-func (t *track) onError(err error) {
+func (track *baseTrack) onError(err error) {
-	t.mu.Lock()
+	track.mu.Lock()
-	t.err = err
+	track.err = err
-	handler := t.onErrorHandler
+	handler := track.onErrorHandler
-	t.mu.Unlock()
+	track.mu.Unlock()
 
 	if handler != nil {
-		t.endOnce.Do(func() {
+		track.endOnce.Do(func() {
 			handler(err)
 		})
 	}
 }
 
-// start starts the data flow from the driver all the way to the localTrack
+func (track *baseTrack) bind(pc *webrtc.PeerConnection, encodedReader codec.ReadCloser, selectedCodec *codec.RTPCodec, sampler func(*webrtc.Track) samplerFunc) (*webrtc.Track, error) {
-func (t *track) start() {
+	track.mu.Lock()
+	defer track.mu.Unlock()
+
+	webrtcTrack, err := pc.NewTrack(selectedCodec.PayloadType, rand.Uint32(), track.ID(), selectedCodec.MimeType)
+	if err != nil {
+		return nil, err
+	}
+
+	sample := sampler(webrtcTrack)
+	signalCh := make(chan chan<- struct{})
+	track.activePeerConnections[pc] = signalCh
+
+	fmt.Println("Binding")
+
+	go func() {
+		var doneCh chan<- struct{}
+		defer func() {
+			encodedReader.Close()
+
+			// When there's another call to unbind, it won't block since we mark the signalCh to be closed
+			close(signalCh)
+			if doneCh != nil {
+				close(doneCh)
+			}
+		}()
+
 		for {
-		buff, _, err := t.encoder.Read()
+			select {
+			case doneCh = <-signalCh:
+				return
+			default:
+			}
+
+			buff, _, err := encodedReader.Read()
 			if err != nil {
-			t.onError(err)
+				track.onError(err)
 				return
 			}
 
-		if err := t.sample(buff); err != nil {
+			if err := sample(buff); err != nil {
-			t.onError(err)
+				track.onError(err)
 				return
 			}
 		}
+	}()
+
+	return webrtcTrack, nil
 }
 
-// Stop stops the underlying driver and encoder
+func (track *baseTrack) unbind(pc *webrtc.PeerConnection) error {
-func (t *track) Stop() {
+	track.mu.Lock()
-	t.d.Close()
+	defer track.mu.Unlock()
-	t.encoder.Close()
+
+	ch, ok := track.activePeerConnections[pc]
+	if !ok {
+		return errNotFoundPeerConnection
 	}
 
-func (t *track) Track() *webrtc.Track {
+	doneCh := make(chan struct{})
-	return t.localTrack.(*webrtc.Track)
+	ch <- doneCh
+	<-doneCh
+	delete(track.activePeerConnections, pc)
+	return nil
 }
 
-func (t *track) LocalTrack() LocalTrack {
+func newTrackFromDriver(d driver.Driver, constraints MediaTrackConstraints, selector *CodecSelector) (Track, error) {
-	return t.localTrack
+	if err := d.Open(); err != nil {
+		return nil, err
 	}
 
-// encoderBuilder is a generic encoder builder that acts as a delegator for codec.VideoEncoderBuilder and
+	switch recorder := d.(type) {
-// codec.AudioEncoderBuilder. The idea of having a delegator is to reduce redundant codes that are being
+	case driver.VideoRecorder:
-// duplicated for managing video and audio.
+		return newVideoTrackFromDriver(d, recorder, constraints, selector)
-type encoderBuilder struct {
+	case driver.AudioRecorder:
-	name  string
+		return newAudioTrackFromDriver(d, recorder, constraints, selector)
-	build func() (codec.ReadCloser, error)
+	default:
+		panic(errInvalidDriverType)
+	}
 }
 
-// newVideoEncoderBuilders transforms video given by VideoRecorder with the video transformer that is passed through
+// VideoTrack is a specific track type that contains video source which allows multiple readers to access, and manipulate.
-// constraints and create a list of generic encoder builders
+type VideoTrack struct {
-func newVideoEncoderBuilders(vr driver.VideoRecorder, constraints MediaTrackConstraints) ([]encoderBuilder, error) {
+	*baseTrack
-	r, err := vr.VideoRecord(constraints.selectedMedia)
+	*video.Broadcaster
+}
+
+// NewVideoTrack constructs a new VideoTrack
+func NewVideoTrack(source VideoSource, selector *CodecSelector) Track {
+	return newVideoTrackFromReader(source, source, selector)
+}
+
+func newVideoTrackFromReader(source Source, reader video.Reader, selector *CodecSelector) Track {
+	base := newBaseTrack(source, VideoInput, selector)
+	wrappedReader := video.ReaderFunc(func() (img image.Image, release func(), err error) {
+		img, _, err = reader.Read()
+		if err != nil {
+			base.onError(err)
+		}
+		return img, func() {}, err
+	})
+
+	// TODO: Allow users to configure broadcaster
+	broadcaster := video.NewBroadcaster(wrappedReader, nil)
+
+	return &VideoTrack{
+		baseTrack:   base,
+		Broadcaster: broadcaster,
+	}
+}
+
+// newVideoTrackFromDriver is an internal video track creation from driver
+func newVideoTrackFromDriver(d driver.Driver, recorder driver.VideoRecorder, constraints MediaTrackConstraints, selector *CodecSelector) (Track, error) {
+	reader, err := recorder.VideoRecord(constraints.selectedMedia)
 	if err != nil {
 		return nil, err
 	}
 
-	if constraints.VideoTransform != nil {
+	return newVideoTrackFromReader(d, reader, selector), nil
-		r = constraints.VideoTransform(r)
 }
 
-	encoderBuilders := make([]encoderBuilder, len(constraints.VideoEncoderBuilders))
+// Transform transforms the underlying source by applying the given fns in serial order
-	for i, b := range constraints.VideoEncoderBuilders {
+func (track *VideoTrack) Transform(fns ...video.TransformFunc) {
-		encoderBuilders[i].name = b.RTPCodec().Name
+	src := track.Broadcaster.Source()
-		encoderBuilders[i].build = func() (codec.ReadCloser, error) {
+	track.Broadcaster.ReplaceSource(video.Merge(fns...)(src))
-			return b.BuildVideoEncoder(r, constraints.selectedMedia)
-		}
-	}
-	return encoderBuilders, nil
 }
 
-// newAudioEncoderBuilders transforms audio given by AudioRecorder with the audio transformer that is passed through
+func (track *VideoTrack) Bind(pc *webrtc.PeerConnection) (*webrtc.Track, error) {
-// constraints and create a list of generic encoder builders
+	reader := track.NewReader(false)
-func newAudioEncoderBuilders(ar driver.AudioRecorder, constraints MediaTrackConstraints) ([]encoderBuilder, error) {
+	inputProp, err := detectCurrentVideoProp(track.Broadcaster)
-	r, err := ar.AudioRecord(constraints.selectedMedia)
 	if err != nil {
 		return nil, err
 	}
 
-	if constraints.AudioTransform != nil {
+	wantCodecs := pc.GetRegisteredRTPCodecs(webrtc.RTPCodecTypeVideo)
-		r = constraints.AudioTransform(r)
+	fmt.Println(wantCodecs)
+	fmt.Println(&inputProp)
+	encodedReader, selectedCodec, err := track.selector.selectVideoCodec(wantCodecs, reader, inputProp)
+	if err != nil {
+		return nil, err
 	}
 
-	encoderBuilders := make([]encoderBuilder, len(constraints.AudioEncoderBuilders))
+	return track.bind(pc, encodedReader, selectedCodec, newVideoSampler)
-	for i, b := range constraints.AudioEncoderBuilders {
+}
-		encoderBuilders[i].name = b.RTPCodec().Name
+
-		encoderBuilders[i].build = func() (codec.ReadCloser, error) {
+func (track *VideoTrack) Unbind(pc *webrtc.PeerConnection) error {
-			return b.BuildAudioEncoder(r, constraints.selectedMedia)
+	return track.unbind(pc)
+}
+
+// AudioTrack is a specific track type that contains audio source which allows multiple readers to access, and
+// manipulate.
+type AudioTrack struct {
+	*baseTrack
+	*audio.Broadcaster
+}
+
+// NewAudioTrack constructs a new VideoTrack
+func NewAudioTrack(source AudioSource, selector *CodecSelector) Track {
+	return newAudioTrackFromReader(source, source, selector)
+}
+
+func newAudioTrackFromReader(source Source, reader audio.Reader, selector *CodecSelector) Track {
+	base := newBaseTrack(source, AudioInput, selector)
+	wrappedReader := audio.ReaderFunc(func() (chunk wave.Audio, release func(), err error) {
+		chunk, _, err = reader.Read()
+		if err != nil {
+			base.onError(err)
+		}
+		return chunk, func() {}, err
+	})
+
+	// TODO: Allow users to configure broadcaster
+	broadcaster := audio.NewBroadcaster(wrappedReader, nil)
+
+	return &AudioTrack{
+		baseTrack:   base,
+		Broadcaster: broadcaster,
 	}
 }
-	return encoderBuilders, nil
+
+// newAudioTrackFromDriver is an internal audio track creation from driver
+func newAudioTrackFromDriver(d driver.Driver, recorder driver.AudioRecorder, constraints MediaTrackConstraints, selector *CodecSelector) (Track, error) {
+	reader, err := recorder.AudioRecord(constraints.selectedMedia)
+	if err != nil {
+		return nil, err
+	}
+
+	return newAudioTrackFromReader(d, reader, selector), nil
+}
+
+// Transform transforms the underlying source by applying the given fns in serial order
+func (track *AudioTrack) Transform(fns ...audio.TransformFunc) {
+	src := track.Broadcaster.Source()
+	track.Broadcaster.ReplaceSource(audio.Merge(fns...)(src))
+}
+
+func (track *AudioTrack) Bind(pc *webrtc.PeerConnection) (*webrtc.Track, error) {
+	reader := track.NewReader(false)
+	inputProp, err := detectCurrentAudioProp(track.Broadcaster)
+	if err != nil {
+		return nil, err
+	}
+
+	wantCodecs := pc.GetRegisteredRTPCodecs(webrtc.RTPCodecTypeAudio)
+	encodedReader, selectedCodec, err := track.selector.selectAudioCodec(wantCodecs, reader, inputProp)
+	if err != nil {
+		return nil, err
+	}
+
+	return track.bind(pc, encodedReader, selectedCodec, func(t *webrtc.Track) samplerFunc { return newAudioSampler(t, inputProp.Latency) })
+}
+
+func (track *AudioTrack) Unbind(pc *webrtc.PeerConnection) error {
+	return track.unbind(pc)
 }

track_test.go

@@ -10,7 +10,7 @@ func TestOnEnded(t *testing.T) {
 	errExpected := errors.New("an error")
 
 	t.Run("ErrorAfterRegister", func(t *testing.T) {
-		tr := &track{}
+		tr := &baseTrack{}
 
 		called := make(chan error, 1)
 		tr.OnEnded(func(error) {
@@ -35,7 +35,7 @@ func TestOnEnded(t *testing.T) {
 	})
 
 	t.Run("ErrorBeforeRegister", func(t *testing.T) {
-		tr := &track{}
+		tr := &baseTrack{}
 
 		tr.onError(errExpected)