Use new intervalpli interceptor in examples

Instead of manually spawning a goroutine this demonstrates how an
interceptor can be useful.

Co-authored-by: Antoine Baché <antoine@tenten.app>

examples/save-to-disk/main.go

@@ -8,10 +8,9 @@ import (
 	"fmt"
 	"os"
 	"strings"
-	"time"
 
 	"github.com/pion/interceptor"
-	"github.com/pion/rtcp"
+	"github.com/pion/interceptor/pkg/intervalpli"
 	"github.com/pion/webrtc/v3"
 	"github.com/pion/webrtc/v3/examples/internal/signal"
 	"github.com/pion/webrtc/v3/pkg/media"
@@ -65,8 +64,18 @@ func main() {
 	// for each PeerConnection.
 	i := &interceptor.Registry{}
 
+	// Register a intervalpli factory
+	// This interceptor sends a PLI every 3 seconds. A PLI causes a video keyframe to be generated by the sender.
+	// This makes our video seekable and more error resilent, but at a cost of lower picture quality and higher bitrates
+	// A real world application should process incoming RTCP packets from viewers and forward them to senders
+	intervalPliFactory, err := intervalpli.NewReceiverInterceptor()
+	if err != nil {
+		panic(err)
+	}
+	i.Add(intervalPliFactory)
+
 	// Use the default set of Interceptors
-	if err := webrtc.RegisterDefaultInterceptors(m, i); err != nil {
+	if err = webrtc.RegisterDefaultInterceptors(m, i); err != nil {
 		panic(err)
 	}
 
@@ -108,17 +117,6 @@ func main() {
 	// an ivf file, since we could have multiple video tracks we provide a counter.
 	// In your application this is where you would handle/process video
 	peerConnection.OnTrack(func(track *webrtc.TrackRemote, receiver *webrtc.RTPReceiver) {
-		// Send a PLI on an interval so that the publisher is pushing a keyframe every rtcpPLIInterval
-		go func() {
-			ticker := time.NewTicker(time.Second * 3)
-			for range ticker.C {
-				errSend := peerConnection.WriteRTCP([]rtcp.Packet{&rtcp.PictureLossIndication{MediaSSRC: uint32(track.SSRC())}})
-				if errSend != nil {
-					fmt.Println(errSend)
-				}
-			}
-		}()
-
 		codec := track.Codec()
 		if strings.EqualFold(codec.MimeType, webrtc.MimeTypeOpus) {
 			fmt.Println("Got Opus track, saving to disk as output.opus (48 kHz, 2 channels)")