init

Signed-off-by: Hadi <[email protected]>

internal/audio/level.go

@@ -0,0 +1,87 @@
+package audio
+
+import (
+	"encoding/binary"
+	"io"
+	"math"
+	"os/exec"
+	"strconv"
+)
+
+// levelSampleRate and levelFrameSamples pick a small chunk size (~100ms) so
+// the UI can poll for a fresh peak reading at a responsive rate without
+// reading much audio data.
+const (
+	levelSampleRate  = 16000
+	levelFrameFrames = levelSampleRate / 10 // 100ms
+	levelFrameBytes  = levelFrameFrames * 4 // 4 bytes per float32 sample
+)
+
+// LevelMonitor streams raw audio from a source and reports its peak
+// amplitude in short chunks, for a live input-level meter. Callers must call
+// Stop when done to release the underlying pw-cat process.
+type LevelMonitor struct {
+	cmd    *exec.Cmd
+	stdout io.ReadCloser
+}
+
+// StartLevelMonitor begins capturing raw audio from sourceID.
+func StartLevelMonitor(sourceID string) (*LevelMonitor, error) {
+	target, err := nodeTarget(sourceID)
+	if err != nil {
+		return nil, err
+	}
+
+	cmd := exec.Command("pw-cat", // #nosec G204 -- target is a node.name read back from `wpctl inspect`, never shell-interpreted
+		"--record",
+		"--target", target,
+		"--format", "f32",
+		"--rate", strconv.Itoa(levelSampleRate),
+		"--channels", "1",
+		"--raw",
+		"-",
+	)
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+	return &LevelMonitor{cmd: cmd, stdout: stdout}, nil
+}
+
+// Next blocks until one ~100ms chunk of audio has been captured and returns
+// its peak amplitude as a value in [0, 1]. It returns an error once the
+// monitor is stopped or the source disappears.
+func (l *LevelMonitor) Next() (float64, error) {
+	buf := make([]byte, levelFrameBytes)
+	n, err := io.ReadFull(l.stdout, buf)
+	if n == 0 {
+		return 0, err
+	}
+
+	var peak float32
+	for i := 0; i+4 <= n; i += 4 {
+		v := math.Float32frombits(binary.LittleEndian.Uint32(buf[i : i+4]))
+		if v < 0 {
+			v = -v
+		}
+		if v > peak {
+			peak = v
+		}
+	}
+	if peak > 1 {
+		peak = 1
+	}
+	return float64(peak), nil
+}
+
+// Stop terminates the capture process. Safe to call more than once.
+func (l *LevelMonitor) Stop() {
+	if l.cmd.Process != nil {
+		_ = l.cmd.Process.Kill()
+	}
+	_ = l.cmd.Wait()
+}