pipewire: Add experimental PipeWire support

This implements a PipeWire capture device which can be used as an input
source instead of the already available URL input.

Known issues with the current PipeWire support are:

- user has to connect the monitor of the default audio sink to the
  capture device manually
- correct shutdown has to be tested
- multiple instances do not work
- medium code quality requires refactoring

Since this is nevertheless usable and possible unknown bugs should be
figured out in practise soon this implementation is already added.
Bugfixes and refactoring might follow.

1 files changed, 80 insertions, 0 deletions

diff --git a/soundbox/pipewire.go b/soundbox/pipewire.go
new file mode 100644
index 0000000..fbae73b
--- /dev/null
+++ b/soundbox/pipewire.go
@@ -0,0 +1,80 @@
+package soundbox
+
+/*
+#cgo pkg-config: libpipewire-0.3
+#include "pipewire-binding.h"
+*/
+import "C"
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"net"
+	"log"
+	"os/exec"
+	"unsafe"
+)
+
+var pipewireAudio = make(chan []byte, 5)
+
+func StreamPipewireContext(ctx context.Context, targets []net.HardwareAddr) error {
+	cmd := exec.CommandContext(
+		ctx,
+		"ffmpeg",
+		"-ac",
+		"2",
+		"-ar",
+		"48000",
+		"-f",
+		"s16le",
+		"-channel_layout",
+		"stereo",
+		"-i",
+		"-",
+		"-acodec",
+		"flac",
+		"-f",
+		"ogg",
+		"-",
+	)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return err
+	}
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	go C.pw_stdout()
+
+	go func() {
+		for buffer := range pipewireAudio {
+			tempReader := bytes.NewReader(buffer)
+			_, err := io.Copy(stdin, tempReader)
+			if err != nil {
+				log.Println("Failed to copy from PipeWire to ffmpeg.")
+				break
+			}
+		}
+	}()
+
+	err = cmd.Start()
+	if err != nil {
+		return err
+	}
+
+	err = streamContext(ctx, stdout, targets)
+	if err != nil {
+		return err
+	}
+
+	return cmd.Wait()
+}
+
+//export goHandleData
+func goHandleData(data *C.int16_t, size C.size_t) {
+	buf := C.GoBytes(unsafe.Pointer(data), C.int(size))
+	pipewireAudio <- buf
+}