enable ffmpeg functionality outside the GUI paths

the GUI creates TVPayload directly, and supplies FFmpegPath. the other code paths use NewTVPayload to construct the TVPayload. assigning FFmpegPath here makes sure that the Transcode option can actually be supported.

soapcalls/soapcalls.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"io"
 	"net/url"
+	"os/exec"
 	"time"
 
 	"github.com/alexballas/go2tv/soapcalls/utils"
@@ -45,6 +46,8 @@ func NewTVPayload(o *Options) (*TVPayload, error) {
 		return nil, err
 	}
 
+	ffmpegPath, _ := exec.LookPath("ffmpeg")
+
 	return &TVPayload{
 		ControlURL:                  upnpServicesURLs.AvtransportControlURL,
 		EventURL:                    upnpServicesURLs.AvtransportEventSubURL,
@@ -61,6 +64,8 @@ func NewTVPayload(o *Options) (*TVPayload, error) {
 		Transcode:                   o.Transcode,
 		Seekable:                    o.Seek,
 		LogOutput:                   o.LogOutput,
+		FFmpegPath:                  ffmpegPath,
+		FFmpegSubsPath:              o.Subs,
 	}, nil
 }