feat(audio): T-0.3 spike lolos — engine oto v3.5.1 async + fallback anggun (F-024 awal)

internal/audio/wav.go

@@ -0,0 +1,51 @@
+package audio
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+)
+
+// ParsePCM memvalidasi file WAV (RIFF) dan mengembalikan isi chunk "data" (PCM).
+// Standar aset tia (PRD Appendix C): 44.1 kHz, mono, 16-bit — selain itu ditolak
+// agar kesalahan aset ketahuan saat dev, bukan saat runtime.
+func ParsePCM(b []byte) ([]byte, error) {
+	if len(b) < 44 || string(b[0:4]) != "RIFF" || string(b[8:12]) != "WAVE" {
+		return nil, errors.New("bukan file RIFF/WAVE")
+	}
+	var (
+		format, channels, bits, rate int
+		data                         []byte
+	)
+	for off := 12; off+8 <= len(b); {
+		id := string(b[off : off+4])
+		size := int(binary.LittleEndian.Uint32(b[off+4 : off+8]))
+		off += 8
+		if size < 0 || off+size > len(b) {
+			return nil, fmt.Errorf("chunk %q terpotong", id)
+		}
+		switch id {
+		case "fmt ":
+			if size < 16 {
+				return nil, errors.New("chunk fmt terlalu pendek")
+			}
+			format = int(binary.LittleEndian.Uint16(b[off : off+2]))
+			channels = int(binary.LittleEndian.Uint16(b[off+2 : off+4]))
+			rate = int(binary.LittleEndian.Uint32(b[off+4 : off+8]))
+			bits = int(binary.LittleEndian.Uint16(b[off+14 : off+16]))
+		case "data":
+			data = b[off : off+size]
+		}
+		off += size + size%2 // chunk berukuran ganjil dipad 1 byte
+	}
+	if format != 1 {
+		return nil, fmt.Errorf("format %d bukan PCM", format)
+	}
+	if channels != 1 || bits != 16 || rate != 44100 {
+		return nil, fmt.Errorf("hanya mono/16-bit/44100Hz didukung (dapat %dch/%dbit/%dHz)", channels, bits, rate)
+	}
+	if len(data) == 0 {
+		return nil, errors.New("chunk data kosong")
+	}
+	return data, nil
+}