install go2rtc on bob

installs_on_host/go2rtc/internal/webrtc/client_creality.go

@@ -0,0 +1,152 @@
+package webrtc
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/AlexxIT/go2rtc/pkg/core"
+	"github.com/AlexxIT/go2rtc/pkg/webrtc"
+	"github.com/pion/sdp/v3"
+)
+
+// https://github.com/AlexxIT/go2rtc/issues/1600
+func crealityClient(url string) (core.Producer, error) {
+	pc, err := PeerConnection(true)
+	if err != nil {
+		return nil, err
+	}
+
+	prod := webrtc.NewConn(pc)
+	prod.FormatName = "webrtc/creality"
+	prod.Mode = core.ModeActiveProducer
+	prod.Protocol = "http"
+	prod.URL = url
+
+	medias := []*core.Media{
+		{Kind: core.KindVideo, Direction: core.DirectionRecvonly},
+	}
+
+	// TODO: return webrtc.SessionDescription
+	offer, err := prod.CreateCompleteOffer(medias)
+	if err != nil {
+		return nil, err
+	}
+
+	log.Trace().Msgf("[webrtc] offer:\n%s", offer)
+
+	body, err := offerToB64(offer)
+	if err != nil {
+		return nil, err
+	}
+
+	req, err := http.NewRequest("POST", url, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "plain/text")
+
+	// TODO: change http.DefaultClient settings
+	client := http.Client{Timeout: time.Second * 5000}
+	defer client.CloseIdleConnections()
+
+	res, err := client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	answer, err := answerFromB64(res.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	log.Trace().Msgf("[webrtc] answer:\n%s", answer)
+
+	if answer, err = fixCrealitySDP(answer); err != nil {
+		return nil, err
+	}
+
+	if err = prod.SetAnswer(answer); err != nil {
+		return nil, err
+	}
+
+	return prod, nil
+}
+
+func offerToB64(sdp string) (io.Reader, error) {
+	// JS object
+	v := map[string]string{
+		"type": "offer",
+		"sdp":  sdp,
+	}
+
+	// bytes
+	b, err := json.Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+
+	// base64, why? who knows...
+	s := base64.StdEncoding.EncodeToString(b)
+
+	return strings.NewReader(s), nil
+}
+
+func answerFromB64(r io.Reader) (string, error) {
+	// base64
+	b, err := io.ReadAll(r)
+	if err != nil {
+		return "", err
+	}
+
+	// bytes
+	if b, err = base64.StdEncoding.DecodeString(string(b)); err != nil {
+		return "", err
+	}
+
+	// JS object
+	var v map[string]string
+	if err = json.Unmarshal(b, &v); err != nil {
+		return "", err
+	}
+
+	// string "v=0..."
+	return v["sdp"], nil
+}
+
+func fixCrealitySDP(value string) (string, error) {
+	var sd sdp.SessionDescription
+	if err := sd.UnmarshalString(value); err != nil {
+		return "", err
+	}
+
+	md := sd.MediaDescriptions[0]
+
+	// important to skip first codec, because second codec will be used
+	skip := md.MediaName.Formats[0]
+	md.MediaName.Formats = md.MediaName.Formats[1:]
+
+	attrs := make([]sdp.Attribute, 0, len(md.Attributes))
+	for _, attr := range md.Attributes {
+		switch attr.Key {
+		case "fmtp", "rtpmap":
+			// important to skip fmtp with x-google, because this is second fmtp for same codec
+			// and pion library will fail parsing this SDP
+			if strings.HasPrefix(attr.Value, skip) || strings.Contains(attr.Value, "x-google") {
+				continue
+			}
+		}
+		attrs = append(attrs, attr)
+	}
+
+	md.Attributes = attrs
+
+	b, err := sd.Marshal()
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}