Allow to use user defined Track

Add WithTrackGenerator option to specify TrackGenerator.
This allows user to replace Track by user defined one that
has WriteSample() and Codec() interface.

mediadevices.go

@@ -20,7 +20,7 @@ type MediaDevices interface {
 // 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) MediaDevices {
+func NewMediaDevices(pc *webrtc.PeerConnection, opts ...MediaDevicesOption) MediaDevices {
 	codecs := make(map[webrtc.RTPCodecType][]*webrtc.RTPCodec)
 	for _, kind := range []webrtc.RTPCodecType{
 		webrtc.RTPCodecTypeAudio,
@@ -28,20 +28,51 @@ func NewMediaDevices(pc *webrtc.PeerConnection) MediaDevices {
 	} {
 		codecs[kind] = pc.GetRegisteredRTPCodecs(kind)
 	}
-
-	return &mediaDevices{codecs}
+	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) MediaDevices {
-	return &mediaDevices{codecs}
+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 {
-	codecs map[webrtc.RTPCodecType][]*webrtc.RTPCodec
+	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
+	}
 }
 
 // GetUserMedia prompts the user for permission to use a media input which produces a MediaStream
@@ -161,7 +192,7 @@ func (m *mediaDevices) selectAudio(constraints MediaTrackConstraints) (Tracker,
 		return nil, err
 	}
 
-	return newAudioTrack(m.codecs[webrtc.RTPCodecTypeAudio], d, c)
+	return newAudioTrack(&m.MediaDevicesOptions, d, c)
 }
 func (m *mediaDevices) selectVideo(constraints MediaTrackConstraints) (Tracker, error) {
 	filter := driver.FilterVideoRecorder()
@@ -178,7 +209,7 @@ func (m *mediaDevices) selectVideo(constraints MediaTrackConstraints) (Tracker,
 		return nil, err
 	}
 
-	return newVideoTrack(m.codecs[webrtc.RTPCodecTypeVideo], d, c)
+	return newVideoTrack(&m.MediaDevicesOptions, d, c)
 }
 
 func (m *mediaDevices) EnumerateDevices() []MediaDeviceInfo {

sampler.go

@@ -3,17 +3,16 @@ package mediadevices
 import (
 	"time"
 
-	"github.com/pion/webrtc/v2"
 	"github.com/pion/webrtc/v2/pkg/media"
 )
 
 type sampler struct {
-	track         *webrtc.Track
+	track         LocalTrack
 	clockRate     float64
 	lastTimestamp time.Time
 }
 
-func newSampler(track *webrtc.Track) *sampler {
+func newSampler(track LocalTrack) *sampler {
 	return &sampler{
 		track:         track,
 		clockRate:     float64(track.Codec().ClockRate),

track.go

@@ -21,14 +21,19 @@ type Tracker interface {
 	OnEnded(func(error))
 }
 
+type LocalTrack interface {
+	WriteSample(s media.Sample) error
+	Codec() *webrtc.RTPCodec
+}
+
 type track struct {
-	t *webrtc.Track
+	t LocalTrack
 	s *sampler
 
 	onErrorHandler atomic.Value // func(error)
 }
 
-func newTrack(codecs []*webrtc.RTPCodec, d driver.Driver, codecName string) (*track, error) {
+func newTrack(codecs []*webrtc.RTPCodec, trackGenerator TrackGenerator, d driver.Driver, codecName string) (*track, error) {
 	var selectedCodec *webrtc.RTPCodec
 	for _, c := range codecs {
 		if c.Name == codecName {
@@ -40,7 +45,7 @@ func newTrack(codecs []*webrtc.RTPCodec, d driver.Driver, codecName string) (*tr
 		return nil, fmt.Errorf("track: %s is not registered in media engine", codecName)
 	}
 
-	t, err := webrtc.NewTrack(
+	t, err := trackGenerator(
 		selectedCodec.PayloadType,
 		rand.Uint32(),
 		d.ID(),
@@ -69,7 +74,7 @@ func (t *track) onError(err error) {
 }
 
 func (t *track) Track() *webrtc.Track {
-	return t.t
+	return t.t.(*webrtc.Track)
 }
 
 type videoTrack struct {
@@ -81,9 +86,9 @@ type videoTrack struct {
 
 var _ Tracker = &videoTrack{}
 
-func newVideoTrack(codecs []*webrtc.RTPCodec, d driver.Driver, constraints MediaTrackConstraints) (*videoTrack, error) {
+func newVideoTrack(opts *MediaDevicesOptions, d driver.Driver, constraints MediaTrackConstraints) (*videoTrack, error) {
 	codecName := constraints.CodecName
-	t, err := newTrack(codecs, d, codecName)
+	t, err := newTrack(opts.codecs[webrtc.RTPCodecTypeVideo], opts.trackGenerator, d, codecName)
 	if err != nil {
 		return nil, err
 	}
@@ -156,9 +161,9 @@ type audioTrack struct {
 
 var _ Tracker = &audioTrack{}
 
-func newAudioTrack(codecs []*webrtc.RTPCodec, d driver.Driver, constraints MediaTrackConstraints) (*audioTrack, error) {
+func newAudioTrack(opts *MediaDevicesOptions, d driver.Driver, constraints MediaTrackConstraints) (*audioTrack, error) {
 	codecName := constraints.CodecName
-	t, err := newTrack(codecs, d, codecName)
+	t, err := newTrack(opts.codecs[webrtc.RTPCodecTypeAudio], opts.trackGenerator, d, codecName)
 	if err != nil {
 		return nil, err
 	}