Rewrite exec backchannel

pkg/pcm/backchannel.go

@@ -0,0 +1,69 @@
+package pcm
+
+import (
+	"errors"
+
+	"github.com/AlexxIT/go2rtc/pkg/core"
+	"github.com/AlexxIT/go2rtc/pkg/shell"
+	"github.com/pion/rtp"
+)
+
+type Backchannel struct {
+	core.Connection
+	cmd *shell.Command
+}
+
+func NewBackchannel(cmd *shell.Command, audio string) (core.Producer, error) {
+	var codec *core.Codec
+
+	if audio == "" {
+		// default codec
+		codec = &core.Codec{Name: core.CodecPCML, ClockRate: 16000}
+	} else if codec = core.ParseCodecString(audio); codec == nil {
+		return nil, errors.New("pcm: unsupported audio format: " + audio)
+	}
+
+	medias := []*core.Media{
+		{
+			Kind:      core.KindAudio,
+			Direction: core.DirectionSendonly,
+			Codecs:    []*core.Codec{codec},
+		},
+	}
+
+	return &Backchannel{
+		Connection: core.Connection{
+			ID:         core.NewID(),
+			FormatName: "pcm",
+			Protocol:   "pipe",
+			Medias:     medias,
+			Transport:  cmd,
+		},
+		cmd: cmd,
+	}, nil
+}
+
+func (c *Backchannel) GetTrack(media *core.Media, codec *core.Codec) (*core.Receiver, error) {
+	return nil, core.ErrCantGetTrack
+}
+
+func (c *Backchannel) AddTrack(media *core.Media, codec *core.Codec, track *core.Receiver) error {
+	wr, err := c.cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	sender := core.NewSender(media, track.Codec)
+	sender.Handler = func(packet *rtp.Packet) {
+		if n, err := wr.Write(packet.Payload); err != nil {
+			c.Send += n
+		}
+	}
+	sender.HandleRTP(track)
+	c.Senders = append(c.Senders, sender)
+	return nil
+}
+
+func (c *Backchannel) Start() error {
+	return c.cmd.Run()
+}