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

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))
+}