pipewire: Make sure only one instance is running

The init / deinit of the PipeWire C library is not well handled for
multiple instances. Furthermore the PipeWire audio streaming relies on a
channel which is a global variable.

Both issues have to be fixed before multiple PipeWire capture instances
are allowed.

1 files changed, 12 insertions, 0 deletions

diff --git a/soundbox/pipewire.go b/soundbox/pipewire.go
index bb672f8..0443766 100644
--- a/soundbox/pipewire.go
+++ b/soundbox/pipewire.go
@@ -8,10 +8,12 @@ import "C"
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"log"
 	"net"
 	"os/exec"
+	"sync"
 	"unsafe"
 )
 
@@ -21,6 +23,10 @@ type pwCapture struct {
 
 var pwAudio chan []byte
 
+// lock makes sure there is always just one PipeWire capture device since
+// multiple are not yet implemented.
+var lock sync.Mutex
+
 func newPWCapture(ctx context.Context) pwCapture {
 	pwc := pwCapture{}
 
@@ -74,6 +80,12 @@ func s16leDropSilence(input []byte) []byte {
 }
 
 func StreamPipewireContext(ctx context.Context, targets []net.HardwareAddr) error {
+	success := lock.TryLock()
+	if !success {
+		return fmt.Errorf("Could not acquire lock")
+	}
+	defer lock.Unlock()
+
 	cmd := exec.CommandContext(
 		ctx,
 		"ffmpeg",