Set video track for WebRTC always first

pkg/webrtc/conn.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"github.com/AlexxIT/go2rtc/pkg/streamer"
 	"github.com/pion/webrtc/v3"
+	"sort"
 )
 
 const (
@@ -100,6 +101,12 @@ func (c *Conn) SetOffer(offer string) (err error) {
 	}
 	rawSDP := []byte(c.Conn.RemoteDescription().SDP)
 	c.medias, err = streamer.UnmarshalSDP(rawSDP)
+
+	// sort medias, so video will always be before audio
+	sort.Slice(c.medias, func(i, j int) bool {
+		return c.medias[i].Kind == streamer.KindVideo
+	})
+
 	return
 }