Add support pipe to exec source

pkg/pipe/producer.go

@@ -0,0 +1,51 @@
+package pipe
+
+import (
+	"encoding/json"
+	"github.com/AlexxIT/go2rtc/pkg/core"
+	"strings"
+)
+
+func (c *Client) GetMedias() []*core.Media {
+	return c.medias
+}
+
+func (c *Client) GetTrack(media *core.Media, codec *core.Codec) (*core.Receiver, error) {
+	if c.receiver == nil {
+		c.receiver = core.NewReceiver(media, codec)
+	}
+	return c.receiver, nil
+}
+
+func (c *Client) Start() error {
+	return c.handle()
+}
+
+func (c *Client) Stop() (err error) {
+	if c.receiver != nil {
+		c.receiver.Close()
+	}
+	if err1 := c.stdout.Close(); err != nil {
+		err = err1
+	}
+	if err1 := c.cmd.Process.Kill(); err != nil {
+		err = err1
+	}
+	if err1 := c.cmd.Wait(); err != nil {
+		err = err1
+	}
+	return
+}
+
+func (c *Client) MarshalJSON() ([]byte, error) {
+	info := &core.Info{
+		Type:   "PIPE active producer",
+		URL:    c.cmd.Path + " " + strings.Join(c.cmd.Args, " "),
+		Medias: c.medias,
+		Recv:   c.recv,
+	}
+	if c.receiver != nil {
+		info.Receivers = append(info.Receivers, c.receiver)
+	}
+	return json.Marshal(info)
+}