add new example client-read-format-mpeg4audio-save-to-disk (#235)

examples/client-read-format-mpeg4audio-save-to-disk/main.go

@@ -0,0 +1,84 @@
+package main
+
+import (
+	"log"
+
+	"github.com/bluenviron/gortsplib/v3"
+	"github.com/bluenviron/gortsplib/v3/pkg/formats"
+	"github.com/bluenviron/gortsplib/v3/pkg/url"
+	"github.com/pion/rtp"
+)
+
+// This example shows how to
+// 1. connect to a RTSP server
+// 2. check if there's an MPEG4-audio media
+// 3. save the content of the media into a file in MPEG-TS format
+
+func main() {
+	c := gortsplib.Client{}
+
+	// parse URL
+	u, err := url.Parse("rtsp://localhost:8554/mystream")
+	if err != nil {
+		panic(err)
+	}
+
+	// connect to the server
+	err = c.Start(u.Scheme, u.Host)
+	if err != nil {
+		panic(err)
+	}
+	defer c.Close()
+
+	// find published medias
+	medias, baseURL, _, err := c.Describe(u)
+	if err != nil {
+		panic(err)
+	}
+
+	// find the MPEG4-audio media and format
+	var forma *formats.MPEG4Audio
+	medi := medias.FindFormat(&forma)
+	if medi == nil {
+		panic("media not found")
+	}
+
+	// setup RTP/MPEG4-audio -> MPEG4-audio decoder
+	rtpDec := forma.CreateDecoder()
+
+	// setup MPEG4-audio -> MPEG-TS muxer
+	mpegtsMuxer, err := newMPEGTSMuxer(forma.Config)
+	if err != nil {
+		panic(err)
+	}
+
+	// setup a single media
+	_, err = c.Setup(medi, baseURL, 0, 0)
+	if err != nil {
+		panic(err)
+	}
+
+	// called when a RTP packet arrives
+	c.OnPacketRTP(medi, forma, func(pkt *rtp.Packet) {
+		// extract access units from RTP packets
+		aus, pts, err := rtpDec.Decode(pkt)
+		if err != nil {
+			log.Printf("ERR: %v", err)
+			return
+		}
+
+		for _, au := range aus {
+			// encode the access unit into MPEG-TS
+			mpegtsMuxer.encode(au, pts)
+		}
+	})
+
+	// start playing
+	_, err = c.Play(nil)
+	if err != nil {
+		panic(err)
+	}
+
+	// wait until a fatal error
+	panic(c.Wait())
+}

examples/client-read-format-mpeg4audio-save-to-disk/mpegtsmuxer.go

@@ -0,0 +1,91 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"log"
+	"os"
+	"time"
+
+	"github.com/asticode/go-astits"
+	"github.com/bluenviron/mediacommon/pkg/codecs/mpeg4audio"
+)
+
+// mpegtsMuxer allows to save a MPEG4-audio stream into a MPEG-TS file.
+type mpegtsMuxer struct {
+	config *mpeg4audio.Config
+	f      *os.File
+	b      *bufio.Writer
+	mux    *astits.Muxer
+}
+
+// newMPEGTSMuxer allocates a mpegtsMuxer.
+func newMPEGTSMuxer(config *mpeg4audio.Config) (*mpegtsMuxer, error) {
+	f, err := os.Create("mystream.ts")
+	if err != nil {
+		return nil, err
+	}
+	b := bufio.NewWriter(f)
+
+	mux := astits.NewMuxer(context.Background(), b)
+	mux.AddElementaryStream(astits.PMTElementaryStream{
+		ElementaryPID: 257,
+		StreamType:    astits.StreamTypeAACAudio,
+	})
+	mux.SetPCRPID(257)
+
+	return &mpegtsMuxer{
+		config: config,
+		f:      f,
+		b:      b,
+		mux:    mux,
+	}, nil
+}
+
+// close closes all the mpegtsMuxer resources.
+func (e *mpegtsMuxer) close() {
+	e.b.Flush()
+	e.f.Close()
+}
+
+// encode encodes a MPEG4-audio access unit into MPEG-TS.
+func (e *mpegtsMuxer) encode(au []byte, pts time.Duration) error {
+	// wrap access unit inside an ADTS packet
+	pkts := mpeg4audio.ADTSPackets{
+		{
+			Type:         e.config.Type,
+			SampleRate:   e.config.SampleRate,
+			ChannelCount: e.config.ChannelCount,
+			AU:           au,
+		},
+	}
+	enc, err := pkts.Marshal()
+	if err != nil {
+		return err
+	}
+
+	_, err = e.mux.WriteData(&astits.MuxerData{
+		PID: 257,
+		AdaptationField: &astits.PacketAdaptationField{
+			RandomAccessIndicator: true,
+		},
+		PES: &astits.PESData{
+			Header: &astits.PESHeader{
+				OptionalHeader: &astits.PESOptionalHeader{
+					MarkerBits:      2,
+					PTSDTSIndicator: astits.PTSDTSIndicatorOnlyPTS,
+					PTS:             &astits.ClockReference{Base: int64(pts.Seconds() * 90000)},
+				},
+				PacketLength: uint16(len(enc) + 8),
+				StreamID:     192, // audio
+			},
+			Data: enc,
+		},
+	})
+	if err != nil {
+		return err
+	}
+
+	log.Println("wrote TS packet")
+	return nil
+}