improve examples (#708)

examples/client-record-format-mpeg4audio/main.go

@@ -1,85 +1,129 @@
+//go:build cgo
+
 package main
 
 import (
+	"crypto/rand"
 	"log"
-	"net"
+	"time"
 
 	"github.com/bluenviron/gortsplib/v4"
 	"github.com/bluenviron/gortsplib/v4/pkg/description"
 	"github.com/bluenviron/gortsplib/v4/pkg/format"
 	"github.com/bluenviron/mediacommon/v2/pkg/codecs/mpeg4audio"
-	"github.com/pion/rtp"
 )
 
 // This example shows how to
-// 1. generate a MPEG-4 audio stream and RTP packets with GStreamer
-// 2. connect to a RTSP server, announce an MPEG-4 audio format
-// 3. route the packets from GStreamer to the server
+// 1. connect to a RTSP server, announce a MPEG-4 Audio (AAC) format
+// 2. generate dummy LPCM audio samples
+// 3. encode audio samples with MPEG-4 Audio (AAC)
+// 3. generate RTP packets from MPEG-4 Audio units
+// 4. write RTP packets to the server
+
+// This example requires the FFmpeg libraries, that can be installed with this command:
+// apt install -y libavcodec-dev libswresample-dev gcc pkg-config
+
+func multiplyAndDivide(v, m, d int64) int64 {
+	secs := v / d
+	dec := v % d
+	return (secs*m + dec*m/d)
+}
+
+func randUint32() (uint32, error) {
+	var b [4]byte
+	_, err := rand.Read(b[:])
+	if err != nil {
+		return 0, err
+	}
+	return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3]), nil
+}
 
 func main() {
-	// open a listener to receive RTP/MPEG-4 audio packets
-	pc, err := net.ListenPacket("udp", "localhost:9000")
-	if err != nil {
-		panic(err)
+	// create a description that contains a MPEG-4 Audio format
+	forma := &format.MPEG4Audio{
+		PayloadTyp: 96,
+		Config: &mpeg4audio.Config{
+			Type:         mpeg4audio.ObjectTypeAACLC,
+			SampleRate:   48000,
+			ChannelCount: 2,
+		},
+		SizeLength:       13,
+		IndexLength:      3,
+		IndexDeltaLength: 3,
 	}
-	defer pc.Close()
-
-	log.Println("Waiting for a RTP/MPEG-4 audio stream on UDP port 9000 - you can send one with GStreamer:\n" +
-		"gst-launch-1.0 audiotestsrc freq=300 ! audioconvert ! audioresample ! audio/x-raw,rate=48000" +
-		" ! avenc_aac bitrate=128000 ! rtpmp4gpay ! udpsink host=127.0.0.1 port=9000")
-
-	// wait for first packet
-	buf := make([]byte, 2048)
-	n, _, err := pc.ReadFrom(buf)
-	if err != nil {
-		panic(err)
-	}
-	log.Println("stream connected")
-
-	// create a description that contains a MPEG-4 audio format
 	desc := &description.Session{
 		Medias: []*description.Media{{
-			Type: description.MediaTypeVideo,
-			Formats: []format.Format{&format.MPEG4Audio{
-				PayloadTyp: 96,
-				Config: &mpeg4audio.Config{
-					Type:         mpeg4audio.ObjectTypeAACLC,
-					SampleRate:   48000,
-					ChannelCount: 2,
-				},
-				SizeLength:       13,
-				IndexLength:      3,
-				IndexDeltaLength: 3,
-			}},
+			Type:    description.MediaTypeAudio,
+			Formats: []format.Format{forma},
 		}},
 	}
 
 	// connect to the server and start recording
 	c := gortsplib.Client{}
-	err = c.StartRecording("rtsp://myuser:mypass@localhost:8554/mystream", desc)
+	err := c.StartRecording("rtsp://myuser:mypass@localhost:8554/mystream", desc)
 	if err != nil {
 		panic(err)
 	}
 	defer c.Close()
 
-	var pkt rtp.Packet
-	for {
-		// parse RTP packet
-		err = pkt.Unmarshal(buf[:n])
+	// setup LPCM -> MPEG-4 Audio encoder
+	mp4aEnc := &mp4aEncoder{}
+	err = mp4aEnc.initialize()
+	if err != nil {
+		panic(err)
+	}
+
+	// setup MPEG-4 Audio -> RTP encoder
+	rtpEnc, err := forma.CreateEncoder()
+	if err != nil {
+		panic(err)
+	}
+
+	start := time.Now()
+	prevPTS := int64(0)
+
+	randomStart, err := randUint32()
+	if err != nil {
+		panic(err)
+	}
+
+	// setup a ticker to sleep between writings
+	ticker := time.NewTicker(100 * time.Millisecond)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		// get current timestamp
+		pts := multiplyAndDivide(int64(time.Since(start)), int64(forma.ClockRate()), int64(time.Second))
+
+		// generate dummy LPCM audio samples
+		samples := createDummyAudio(pts, prevPTS)
+
+		// encode samples with MPEG-4 Audio
+		aus, outPTS, err := mp4aEnc.encode(samples)
+		if err != nil {
+			panic(err)
+		}
+		if aus == nil {
+			continue
+		}
+
+		// generate RTP packets from MPEG-4 audio access units
+		pkts, err := rtpEnc.Encode(aus)
 		if err != nil {
 			panic(err)
 		}
 
-		// route RTP packet to the server
-		err = c.WritePacketRTP(desc.Medias[0], &pkt)
-		if err != nil {
-			panic(err)
+		log.Printf("writing RTP packets with PTS=%d, packet count=%d", outPTS, len(pkts))
+
+		for _, pkt := range pkts {
+			pkt.Timestamp += uint32(int64(randomStart) + outPTS)
+
+			err = c.WritePacketRTP(desc.Medias[0], pkt)
+			if err != nil {
+				panic(err)
+			}
 		}
 
-		// read another RTP packet from source
-		n, _, err = pc.ReadFrom(buf)
-		if err != nil {
-			panic(err)
-		}
+		prevPTS = pts
 	}
 }