Add custom video/audio transforms

Resolves https://github.com/pion/mediadevices/issues/31

examples/transform/main.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"fmt"
+	"image"
+
+	"github.com/pion/mediadevices"
+	"github.com/pion/mediadevices/examples/internal/signal"
+	_ "github.com/pion/mediadevices/pkg/codec/openh264" // This is required to register h264 video encoder
+	_ "github.com/pion/mediadevices/pkg/codec/opus"     // This is required to register opus audio encoder
+	_ "github.com/pion/mediadevices/pkg/codec/vpx"
+	"github.com/pion/mediadevices/pkg/frame"
+	"github.com/pion/mediadevices/pkg/io/video"
+	"github.com/pion/webrtc/v2"
+)
+
+const (
+	videoCodecName = webrtc.VP8
+)
+
+func removeBlue(r video.Reader) video.Reader {
+	return video.ReaderFunc(func() (img image.Image, err error) {
+		img, err = r.Read()
+		if err != nil {
+			return
+		}
+
+		yuvImg, ok := img.(*image.YCbCr)
+		if !ok {
+			return img, nil
+		}
+
+		yuvImg.Cb = make([]uint8, len(yuvImg.Cb))
+		return
+	})
+}
+
+func main() {
+	config := webrtc.Configuration{
+		ICEServers: []webrtc.ICEServer{
+			{
+				URLs: []string{"stun:stun.l.google.com:19302"},
+			},
+		},
+	}
+
+	// Wait for the offer to be pasted
+	offer := webrtc.SessionDescription{}
+	signal.Decode(signal.MustReadStdin(), &offer)
+
+	// Create a new RTCPeerConnection
+	mediaEngine := webrtc.MediaEngine{}
+	if err := mediaEngine.PopulateFromSDP(offer); err != nil {
+		panic(err)
+	}
+	api := webrtc.NewAPI(webrtc.WithMediaEngine(mediaEngine))
+	peerConnection, err := api.NewPeerConnection(config)
+	if err != nil {
+		panic(err)
+	}
+
+	// Set the handler for ICE connection state
+	// This will notify you when the peer has connected/disconnected
+	peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
+		fmt.Printf("Connection State has changed %s \n", connectionState.String())
+	})
+
+	md := mediadevices.NewMediaDevices(peerConnection)
+
+	s, err := md.GetUserMedia(mediadevices.MediaStreamConstraints{
+		Audio: func(c *mediadevices.MediaTrackConstraints) {
+			c.CodecName = webrtc.Opus
+			c.Enabled = true
+			c.BitRate = 32000 // 32kbps
+		},
+		Video: func(c *mediadevices.MediaTrackConstraints) {
+			c.CodecName = videoCodecName
+			c.FrameFormat = frame.FormatI420 // most of the encoder accepts I420
+			c.Enabled = true
+			c.Width = 640
+			c.Height = 480
+			c.BitRate = 100000 // 100kbps
+			c.VideoTransform = removeBlue
+		},
+	})
+	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",
+				t.ID(), t.Label(), err)
+		})
+		_, err = peerConnection.AddTrack(t)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	// Tweak transceiver direction to work with Firefox
+	for _, t := range peerConnection.GetTransceivers() {
+		t.Direction = webrtc.RTPTransceiverDirectionSendonly
+	}
+
+	// Set the remote SessionDescription
+	err = peerConnection.SetRemoteDescription(offer)
+	if err != nil {
+		panic(err)
+	}
+
+	// Create an answer
+	answer, err := peerConnection.CreateAnswer(nil)
+	if err != nil {
+		panic(err)
+	}
+
+	// Sets the LocalDescription, and starts our UDP listeners
+	err = peerConnection.SetLocalDescription(answer)
+	if err != nil {
+		panic(err)
+	}
+
+	// Output the answer in base64 so we can paste it in browser
+	fmt.Println(signal.Encode(answer))
+	select {}
+}