streaming

commit 97693535acd9ae096cffa7e635491aa97264c4a1
parent 5e057162d97599b2803923f2450d38d26c9833f0
Author: Oliver Lowe <o@olowe.co>
Date:   Thu,  1 Aug 2024 18:44:56 +1000

cmd/autx: import audio transmit program

This is a fun test of our RTP and SDP packages. From the docs:
"Command autx transmits audio over the network via RTP."

Diffstat:
A
cmd/autx/autx.go
 | 
110
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 110 insertions(+), 0 deletions(-)
diff --git a/cmd/autx/autx.go b/cmd/autx/autx.go
@@ -0,0 +1,110 @@
+// Command autx transmits audio over the network via RTP.
+// It reads raw audio from the standard input
+// and transmits it to the provided address.
+// Audio must be single-channel (mono),
+// signed 16-bit linear PCM data in big-endian byte order.
+// The sample rate must be 44.1KHz.
+//
+// Its usage is:
+//
+//	autx address
+//
+// Address is in addr:port format.
+//
+// # Example
+//
+// Transmit audio from the file "test.pcm" to 2001:db8::1 port 9999:
+//
+//	autx [2001:db8::1]:9999 < test.pcm
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"time"
+
+	"github.com/untangledco/streaming/rtp"
+	"github.com/untangledco/streaming/sdp"
+)
+
+// 1441kbps in bytes per 20 milliseconds
+const bufSize int = 1411 / 8 * 20
+const packetInterval = 20 * time.Millisecond // from RFC 3xxx
+
+const usage string = "usage: autx address"
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintln(os.Stderr, usage)
+		os.Exit(1)
+	}
+
+	session, err := rtp.Dial("udp", os.Args[1])
+	if err != nil {
+		log.Fatal(err)
+	}
+	session.Clock = 44100 // 44.1KHz
+
+	description := sdp.Session{
+		Origin: sdp.Origin{
+			Username:    sdp.NoUsername,
+			ID:          sdp.Now(),
+			Version:     sdp.Now(),
+			AddressType: "IP6",
+			Address:     "[::1]",
+		},
+		Name: "test",
+		Media: []sdp.Media{
+			{
+				Type:      sdp.MediaTypeAudio,
+				Port:      9999,
+				Transport: sdp.ProtoRTP,
+				Format:    []string{fmt.Sprintf("%d", rtp.PayloadL16)},
+				Attributes: []string{
+					fmt.Sprintf("rtpmap:%d", rtp.PayloadL16),
+					fmt.Sprintf("L16/%d", session.Clock),
+				},
+			},
+		},
+	}
+	fmt.Fprintln(os.Stderr, description)
+
+	out := make(chan rtp.Packet, 100)
+	go func() {
+		buf := &bytes.Buffer{}
+		p := rtp.Packet{
+			Header: rtp.Header{
+				Type: rtp.PayloadL16,
+			},
+		}
+		for {
+			buf.Reset()
+			_, err := io.CopyN(buf, os.Stdin, int64(bufSize))
+			if errors.Is(err, io.EOF) {
+				p.Payload = buf.Bytes()
+				out <- p
+				close(out)
+				return
+			} else if err != nil {
+				log.Println(err)
+			}
+			p.Payload = buf.Bytes()
+			out <- p
+		}
+	}()
+
+	ticker := time.NewTicker(packetInterval)
+	for range ticker.C {
+		p, ok := <-out
+		if !ok {
+			return
+		}
+		if err := session.Transmit(&p); err != nil {
+			log.Println(err)
+		}
+	}
+}