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internal/pipewire/output.go

@@ -0,0 +1,165 @@
+package pipewire
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"os/exec"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+// Output implements the sendspin output.Output interface via pw-cat --playback.
+type Output struct {
+	target   string
+	nodeName string
+
+	mu         sync.Mutex
+	cmd        *exec.Cmd
+	stdin      io.WriteCloser
+	sampleRate int
+	channels   int
+	bitShift   uint
+	buf        []byte
+
+	volume float64
+	muted  bool
+}
+
+func NewOutput(target, nodeName string) *Output {
+	return &Output{
+		target:   target,
+		nodeName: nodeName,
+		volume:   1.0,
+	}
+}
+
+func (o *Output) Open(sampleRate, channels, bitDepth int) error {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+
+	o.sampleRate = sampleRate
+	o.channels = channels
+	// Samples from sendspin are right-justified in int32; shift to fill
+	// the full 32-bit range so pw-cat receives proper amplitude.
+	if bitDepth > 0 && bitDepth < 32 {
+		o.bitShift = uint(32 - bitDepth)
+	} else {
+		o.bitShift = 0
+	}
+	o.killUnlocked()
+	return o.startUnlocked()
+}
+
+func (o *Output) startUnlocked() error {
+	nameJSON, _ := json.Marshal(o.nodeName)
+	props := fmt.Sprintf(`{"node.name":%s}`, nameJSON)
+
+	args := []string{
+		"--playback",
+		"--raw",
+		"--format", "s32",
+		"--rate", strconv.Itoa(o.sampleRate),
+		"--channels", strconv.Itoa(o.channels),
+		"--properties", props,
+	}
+	if o.target != "" {
+		args = append(args, "--target", o.target)
+	}
+	args = append(args, "-")
+
+	cmd := exec.Command("pw-cat", args...)
+
+	stderr, _ := cmd.StderrPipe()
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("pw-cat stdin: %w", err)
+	}
+	if err := cmd.Start(); err != nil {
+		return fmt.Errorf("pw-cat start: %w", err)
+	}
+
+	go func() {
+		b, _ := io.ReadAll(stderr)
+		if s := strings.TrimSpace(string(b)); s != "" {
+			log.Printf("pw-cat stderr: %s", s)
+		}
+	}()
+
+	o.cmd = cmd
+	o.stdin = stdin
+	if o.buf == nil {
+		o.buf = make([]byte, 0, 4096)
+	}
+	return nil
+}
+
+func (o *Output) killUnlocked() {
+	if o.stdin != nil {
+		o.stdin.Close()
+		o.stdin = nil
+	}
+	if o.cmd != nil && o.cmd.Process != nil {
+		o.cmd.Process.Kill()
+		o.cmd.Wait()
+		o.cmd = nil
+	}
+}
+
+func (o *Output) Write(samples []int32) error {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+
+	if o.stdin == nil {
+		return fmt.Errorf("output not opened")
+	}
+
+	need := len(samples) * 4
+	if cap(o.buf) < need {
+		o.buf = make([]byte, need)
+	}
+	o.buf = o.buf[:need]
+
+	for i, s := range samples {
+		if o.muted {
+			s = 0
+		} else if o.volume != 1.0 {
+			s = int32(float64(s) * o.volume)
+		}
+		s <<= o.bitShift
+		binary.LittleEndian.PutUint32(o.buf[i*4:], uint32(s))
+	}
+
+	_, err := o.stdin.Write(o.buf)
+	if err != nil {
+		log.Printf("pw-cat pipe broken (%v), restarting", err)
+		o.killUnlocked()
+		if rerr := o.startUnlocked(); rerr != nil {
+			return fmt.Errorf("pw-cat restart: %w", rerr)
+		}
+		_, err = o.stdin.Write(o.buf)
+	}
+	return err
+}
+
+func (o *Output) SetVolume(volume int) {
+	o.mu.Lock()
+	o.volume = float64(volume) / 100.0
+	o.mu.Unlock()
+}
+
+func (o *Output) SetMuted(muted bool) {
+	o.mu.Lock()
+	o.muted = muted
+	o.mu.Unlock()
+}
+
+func (o *Output) Close() error {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+	o.killUnlocked()
+	return nil
+}